Fix: split index and data file rotation logic
[lttng-tools.git] / src / bin / lttng-relayd / main.c
index 4c99b56f67dcb23ee726b361e96d81d6ba0f0967..1e2e9050fef2d6d77ca78e9767a2fea759ba99be 100644 (file)
 #include <common/sessiond-comm/relayd.h>
 #include <common/uri.h>
 #include <common/utils.h>
+#include <common/align.h>
 #include <common/config/session-config.h>
+#include <common/dynamic-buffer.h>
+#include <common/buffer-view.h>
 #include <urcu/rculist.h>
 
 #include "cmd.h"
@@ -80,6 +83,14 @@ NULL
 #endif
 ;
 
+enum relay_connection_status {
+       RELAY_CONNECTION_STATUS_OK,
+       /* An error occured while processing an event on the connection. */
+       RELAY_CONNECTION_STATUS_ERROR,
+       /* Connection closed/shutdown cleanly. */
+       RELAY_CONNECTION_STATUS_CLOSED,
+};
+
 /* command line options */
 char *opt_output_path;
 static int opt_daemon, opt_background;
@@ -93,6 +104,7 @@ static int lttng_relay_ready = NR_LTTNG_RELAY_READY;
 
 /* Size of receive buffer. */
 #define RECV_DATA_BUFFER_SIZE          65536
+#define FILE_COPY_BUFFER_SIZE          65536
 
 static int recv_child_signal;  /* Set to 1 when a SIGUSR1 signal is received. */
 static pid_t child_ppid;       /* Internal parent PID use with daemonize. */
@@ -143,10 +155,6 @@ static uint64_t last_relay_stream_id;
  */
 static struct relay_conn_queue relay_conn_queue;
 
-/* buffer allocated at startup, used to store the trace data */
-static char *data_buffer;
-static unsigned int data_buffer_size;
-
 /* Global relay stream hash table. */
 struct lttng_ht *relay_streams_ht;
 
@@ -749,6 +757,7 @@ static struct lttcomm_sock *relay_socket_create(struct lttng_uri *uri)
 
        ret = sock->ops->bind(sock);
        if (ret < 0) {
+               PERROR("Failed to bind socket");
                goto error;
        }
 
@@ -1057,35 +1066,39 @@ static int set_index_control_data(struct relay_index *index,
        struct ctf_packet_index index_data;
 
        /*
-        * The index on disk is encoded in big endian, so we don't need
-        * to convert the data received on the network. The data_offset
-        * value is NEVER modified here and is updated by the data
-        * thread.
+        * The index on disk is encoded in big endian.
         */
-       index_data.packet_size = data->packet_size;
-       index_data.content_size = data->content_size;
-       index_data.timestamp_begin = data->timestamp_begin;
-       index_data.timestamp_end = data->timestamp_end;
-       index_data.events_discarded = data->events_discarded;
-       index_data.stream_id = data->stream_id;
+       index_data.packet_size = htobe64(data->packet_size);
+       index_data.content_size = htobe64(data->content_size);
+       index_data.timestamp_begin = htobe64(data->timestamp_begin);
+       index_data.timestamp_end = htobe64(data->timestamp_end);
+       index_data.events_discarded = htobe64(data->events_discarded);
+       index_data.stream_id = htobe64(data->stream_id);
 
        if (conn->minor >= 8) {
-               index->index_data.stream_instance_id = data->stream_instance_id;
-               index->index_data.packet_seq_num = data->packet_seq_num;
+               index->index_data.stream_instance_id = htobe64(data->stream_instance_id);
+               index->index_data.packet_seq_num = htobe64(data->packet_seq_num);
        }
 
        return relay_index_set_data(index, &index_data);
 }
 
+static bool session_streams_have_index(const struct relay_session *session)
+{
+       return session->minor >= 4 && !session->snapshot;
+}
+
 /*
  * Handle the RELAYD_CREATE_SESSION command.
  *
  * On success, send back the session id or else return a negative value.
  */
-static int relay_create_session(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_create_session(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret = 0, send_ret;
+       int ret = 0;
+       ssize_t send_ret;
        struct relay_session *session;
        struct lttcomm_relayd_status_session reply;
        char session_name[LTTNG_NAME_MAX];
@@ -1098,16 +1111,19 @@ static int relay_create_session(struct lttcomm_relayd_hdr *recv_hdr,
 
        memset(&reply, 0, sizeof(reply));
 
-       switch (conn->minor) {
-       case 1:
-       case 2:
-       case 3:
-               break;
-       case 4: /* LTTng sessiond 2.4 */
-       default:
-               ret = cmd_create_session_2_4(conn, session_name,
+       if (conn->minor < 4) {
+               /* From 2.1 to 2.3 */
+               ret = 0;
+       } else if (conn->minor >= 4 && conn->minor < 11) {
+               /* From 2.4 to 2.10 */
+               ret = cmd_create_session_2_4(payload, session_name,
+                       hostname, &live_timer, &snapshot);
+       } else {
+               /* From 2.11 to ... */
+               ret = cmd_create_session_2_11(payload, session_name,
                        hostname, &live_timer, &snapshot);
        }
+
        if (ret < 0) {
                goto send_reply;
        }
@@ -1132,9 +1148,10 @@ send_reply:
        }
 
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (send_ret < 0) {
-               ERR("Relayd sending session id");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"create session\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
        return ret;
@@ -1173,8 +1190,9 @@ static void publish_connection_local_streams(struct relay_connection *conn)
 /*
  * relay_add_stream: allocate a new stream for a session
  */
-static int relay_add_stream(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_add_stream(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
        ssize_t send_ret;
@@ -1185,24 +1203,30 @@ static int relay_add_stream(struct lttcomm_relayd_hdr *recv_hdr,
        uint64_t stream_handle = -1ULL;
        char *path_name = NULL, *channel_name = NULL;
        uint64_t tracefile_size = 0, tracefile_count = 0;
+       struct relay_stream_chunk_id stream_chunk_id = { 0 };
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to add a stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       switch (session->minor) {
-       case 1: /* LTTng sessiond 2.1. Allocates path_name and channel_name. */
-               ret = cmd_recv_stream_2_1(conn, &path_name,
+       if (session->minor == 1) {
+               /* For 2.1 */
+               ret = cmd_recv_stream_2_1(payload, &path_name,
                        &channel_name);
-               break;
-       case 2: /* LTTng sessiond 2.2. Allocates path_name and channel_name. */
-       default:
-               ret = cmd_recv_stream_2_2(conn, &path_name,
+       } else if (session->minor > 1 && session->minor < 11) {
+               /* From 2.2 to 2.10 */
+               ret = cmd_recv_stream_2_2(payload, &path_name,
                        &channel_name, &tracefile_size, &tracefile_count);
-               break;
+       } else {
+               /* From 2.11 to ... */
+               ret = cmd_recv_stream_2_11(payload, &path_name,
+                       &channel_name, &tracefile_size, &tracefile_count,
+                       &stream_chunk_id.value);
+               stream_chunk_id.is_set = true;
        }
+
        if (ret < 0) {
                goto send_reply;
        }
@@ -1219,7 +1243,8 @@ static int relay_add_stream(struct lttcomm_relayd_hdr *recv_hdr,
 
        /* We pass ownership of path_name and channel_name. */
        stream = stream_create(trace, stream_handle, path_name,
-                       channel_name, tracefile_size, tracefile_count);
+               channel_name, tracefile_size, tracefile_count,
+               &stream_chunk_id);
        path_name = NULL;
        channel_name = NULL;
 
@@ -1240,9 +1265,10 @@ send_reply:
 
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
                        sizeof(struct lttcomm_relayd_status_stream), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending stream id");
-               ret = (int) send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"add stream\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -1254,10 +1280,12 @@ end_no_session:
 /*
  * relay_close_stream: close a specific stream
  */
-static int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_close_stream(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret;
+       int ret;
+       ssize_t send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_close_stream stream_info;
        struct lttcomm_relayd_generic_reply reply;
@@ -1265,26 +1293,23 @@ static int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
 
        DBG("Close stream received");
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &stream_info,
-                       sizeof(struct lttcomm_relayd_close_stream), 0);
-       if (ret < sizeof(struct lttcomm_relayd_close_stream)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid add_stream struct size : %d", ret);
-               }
+       if (payload->size < sizeof(stream_info)) {
+               ERR("Unexpected payload size in \"relay_close_stream\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(stream_info), payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&stream_info, payload->data, sizeof(stream_info));
+       stream_info.stream_id = be64toh(stream_info.stream_id);
+       stream_info.last_net_seq_num = be64toh(stream_info.last_net_seq_num);
 
-       stream = stream_get_by_id(be64toh(stream_info.stream_id));
+       stream = stream_get_by_id(stream_info.stream_id);
        if (!stream) {
                ret = -1;
                goto end;
@@ -1295,7 +1320,7 @@ static int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
         * pending check.
         */
        pthread_mutex_lock(&stream->lock);
-       stream->last_net_seq_num = be64toh(stream_info.last_net_seq_num);
+       stream->last_net_seq_num = stream_info.last_net_seq_num;
        pthread_mutex_unlock(&stream->lock);
 
        /*
@@ -1326,6 +1351,7 @@ static int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
                }
        }
        stream_put(stream);
+       ret = 0;
 
 end:
        memset(&reply, 0, sizeof(reply));
@@ -1336,9 +1362,10 @@ end:
        }
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
                        sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending stream id");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"close stream\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -1349,10 +1376,12 @@ end_no_session:
  * relay_reset_metadata: reset a metadata stream
  */
 static
-int relay_reset_metadata(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+int relay_reset_metadata(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret;
+       int ret;
+       ssize_t send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_reset_metadata stream_info;
        struct lttcomm_relayd_generic_reply reply;
@@ -1360,26 +1389,23 @@ int relay_reset_metadata(struct lttcomm_relayd_hdr *recv_hdr,
 
        DBG("Reset metadata received");
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to reset a metadata stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &stream_info,
-                       sizeof(struct lttcomm_relayd_reset_metadata), 0);
-       if (ret < sizeof(struct lttcomm_relayd_reset_metadata)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid reset_metadata struct "
-                                       "size : %d", ret);
-               }
+       if (payload->size < sizeof(stream_info)) {
+               ERR("Unexpected payload size in \"relay_reset_metadata\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(stream_info), payload->size);
                ret = -1;
                goto end_no_session;
        }
-       DBG("Update metadata to version %" PRIu64, be64toh(stream_info.version));
+       memcpy(&stream_info, payload->data, sizeof(stream_info));
+       stream_info.stream_id = be64toh(stream_info.stream_id);
+       stream_info.version = be64toh(stream_info.version);
+
+       DBG("Update metadata to version %" PRIu64, stream_info.version);
 
        /* Unsupported for live sessions for now. */
        if (session->live_timer != 0) {
@@ -1387,7 +1413,7 @@ int relay_reset_metadata(struct lttcomm_relayd_hdr *recv_hdr,
                goto end;
        }
 
-       stream = stream_get_by_id(be64toh(stream_info.stream_id));
+       stream = stream_get_by_id(stream_info.stream_id);
        if (!stream) {
                ret = -1;
                goto end;
@@ -1420,9 +1446,10 @@ end:
        }
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
                        sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending reset metadata reply");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"reset metadata\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -1435,14 +1462,13 @@ end_no_session:
 static void relay_unknown_command(struct relay_connection *conn)
 {
        struct lttcomm_relayd_generic_reply reply;
-       int ret;
+       ssize_t send_ret;
 
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(LTTNG_ERR_UNK);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (ret < 0) {
-               ERR("Relay sending unknown command");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < sizeof(reply)) {
+               ERR("Failed to send \"unknown command\" command reply (ret = %zd)", send_ret);
        }
 }
 
@@ -1450,10 +1476,12 @@ static void relay_unknown_command(struct relay_connection *conn)
  * relay_start: send an acknowledgment to the client to tell if we are
  * ready to receive data. We are ready if a session is established.
  */
-static int relay_start(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_start(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret = htobe32(LTTNG_OK);
+       int ret = 0;
+       ssize_t send_ret;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_session *session = conn->session;
 
@@ -1463,11 +1491,13 @@ static int relay_start(struct lttcomm_relayd_hdr *recv_hdr,
        }
 
        memset(&reply, 0, sizeof(reply));
-       reply.ret_code = ret;
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (ret < 0) {
-               ERR("Relay sending start ack");
+       reply.ret_code = htobe32(LTTNG_OK);
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"relay_start\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
        return ret;
@@ -1504,62 +1534,360 @@ end:
 }
 
 /*
- * relay_recv_metadata: receive the metadata for the session.
+ * Close the current index file if it is open, and create a new one.
+ *
+ * Return 0 on success, -1 on error.
  */
-static int relay_recv_metadata(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static
+int create_rotate_index_file(struct relay_stream *stream,
+               const char *stream_path)
 {
-       int ret = 0;
-       ssize_t size_ret;
-       struct relay_session *session = conn->session;
-       struct lttcomm_relayd_metadata_payload *metadata_struct;
-       struct relay_stream *metadata_stream;
-       uint64_t data_size, payload_size;
+       int ret;
+       uint32_t major, minor;
+
+       /* Put ref on previous index_file. */
+       if (stream->index_file) {
+               lttng_index_file_put(stream->index_file);
+               stream->index_file = NULL;
+       }
+       major = stream->trace->session->major;
+       minor = stream->trace->session->minor;
+       stream->index_file = lttng_index_file_create(stream_path,
+                       stream->channel_name,
+                       -1, -1, stream->tracefile_size,
+                       tracefile_array_get_file_index_head(stream->tfa),
+                       lttng_to_index_major(major, minor),
+                       lttng_to_index_minor(major, minor));
+       if (!stream->index_file) {
+               ret = -1;
+               goto end;
+       }
 
-       if (!session) {
-               ERR("Metadata sent before version check");
+       ret = 0;
+
+end:
+       return ret;
+}
+
+static
+int do_rotate_stream_data(struct relay_stream *stream)
+{
+       int ret;
+
+       DBG("Rotating stream %" PRIu64 " data file",
+                       stream->stream_handle);
+       /* Perform the stream rotation. */
+       ret = utils_rotate_stream_file(stream->path_name,
+                       stream->channel_name, stream->tracefile_size,
+                       stream->tracefile_count, -1,
+                       -1, stream->stream_fd->fd,
+                       NULL, &stream->stream_fd->fd);
+       if (ret < 0) {
+               ERR("Rotating stream output file");
+               goto end;
+       }
+       stream->tracefile_size_current = 0;
+       stream->pos_after_last_complete_data_index = 0;
+       stream->data_rotated = true;
+
+       if (stream->data_rotated && stream->index_rotated) {
+               /* Rotation completed; reset its state. */
+               DBG("Rotation completed for stream %" PRIu64,
+                               stream->stream_handle);
+               stream->rotate_at_seq_num = -1ULL;
+               stream->data_rotated = false;
+               stream->index_rotated = false;
+       }
+end:
+       return ret;
+}
+
+/*
+ * If too much data has been written in a tracefile before we received the
+ * rotation command, we have to move the excess data to the new tracefile and
+ * perform the rotation. This can happen because the control and data
+ * connections are separate, the indexes as well as the commands arrive from
+ * the control connection and we have no control over the order so we could be
+ * in a situation where too much data has been received on the data connection
+ * before the rotation command on the control connection arrives.
+ */
+static
+int rotate_truncate_stream(struct relay_stream *stream)
+{
+       int ret, new_fd;
+       off_t lseek_ret;
+       uint64_t diff, pos = 0;
+       char buf[FILE_COPY_BUFFER_SIZE];
+
+       assert(!stream->is_metadata);
+
+       assert(stream->tracefile_size_current >
+                       stream->pos_after_last_complete_data_index);
+       diff = stream->tracefile_size_current -
+                       stream->pos_after_last_complete_data_index;
+
+       /* Create the new tracefile. */
+       new_fd = utils_create_stream_file(stream->path_name,
+                       stream->channel_name,
+                       stream->tracefile_size, stream->tracefile_count,
+                       /* uid */ -1, /* gid */ -1, /* suffix */ NULL);
+       if (new_fd < 0) {
+               ERR("Failed to create new stream file at path %s for channel %s",
+                               stream->path_name, stream->channel_name);
                ret = -1;
                goto end;
        }
 
-       data_size = payload_size = be64toh(recv_hdr->data_size);
-       if (data_size < sizeof(struct lttcomm_relayd_metadata_payload)) {
-               ERR("Incorrect data size");
+       /*
+        * Rewind the current tracefile to the position at which the rotation
+        * should have occured.
+        */
+       lseek_ret = lseek(stream->stream_fd->fd,
+                       stream->pos_after_last_complete_data_index, SEEK_SET);
+       if (lseek_ret < 0) {
+               PERROR("seek truncate stream");
                ret = -1;
                goto end;
        }
-       payload_size -= sizeof(struct lttcomm_relayd_metadata_payload);
 
-       if (data_buffer_size < data_size) {
-               /* In case the realloc fails, we can free the memory */
-               char *tmp_data_ptr;
+       /* Move data from the old file to the new file. */
+       while (pos < diff) {
+               uint64_t count, bytes_left;
+               ssize_t io_ret;
+
+               bytes_left = diff - pos;
+               count = bytes_left > sizeof(buf) ? sizeof(buf) : bytes_left;
+               assert(count <= SIZE_MAX);
 
-               tmp_data_ptr = realloc(data_buffer, data_size);
-               if (!tmp_data_ptr) {
-                       ERR("Allocating data buffer");
-                       free(data_buffer);
+               io_ret = lttng_read(stream->stream_fd->fd, buf, count);
+               if (io_ret < (ssize_t) count) {
+                       char error_string[256];
+
+                       snprintf(error_string, sizeof(error_string),
+                                       "Failed to read %" PRIu64 " bytes from fd %i in rotate_truncate_stream(), returned %zi",
+                                       count, stream->stream_fd->fd, io_ret);
+                       if (io_ret == -1) {
+                               PERROR("%s", error_string);
+                       } else {
+                               ERR("%s", error_string);
+                       }
+                       ret = -1;
+                       goto end;
+               }
+
+               io_ret = lttng_write(new_fd, buf, count);
+               if (io_ret < (ssize_t) count) {
+                       char error_string[256];
+
+                       snprintf(error_string, sizeof(error_string),
+                                       "Failed to write %" PRIu64 " bytes from fd %i in rotate_truncate_stream(), returned %zi",
+                                       count, new_fd, io_ret);
+                       if (io_ret == -1) {
+                               PERROR("%s", error_string);
+                       } else {
+                               ERR("%s", error_string);
+                       }
                        ret = -1;
                        goto end;
                }
-               data_buffer = tmp_data_ptr;
-               data_buffer_size = data_size;
+
+               pos += count;
        }
-       memset(data_buffer, 0, data_size);
-       DBG2("Relay receiving metadata, waiting for %" PRIu64 " bytes", data_size);
-       size_ret = conn->sock->ops->recvmsg(conn->sock, data_buffer, data_size, 0);
-       if (size_ret < 0 || size_ret != data_size) {
-               if (size_ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive the whole metadata");
+
+       /* Truncate the file to get rid of the excess data. */
+       ret = ftruncate(stream->stream_fd->fd,
+                       stream->pos_after_last_complete_data_index);
+       if (ret) {
+               PERROR("ftruncate");
+               goto end;
+       }
+
+       ret = close(stream->stream_fd->fd);
+       if (ret < 0) {
+               PERROR("Closing tracefile");
+               goto end;
+       }
+
+       /*
+        * Update the offset and FD of all the eventual indexes created by the
+        * data connection before the rotation command arrived.
+        */
+       ret = relay_index_switch_all_files(stream);
+       if (ret < 0) {
+               ERR("Failed to rotate index file");
+               goto end;
+       }
+
+       stream->stream_fd->fd = new_fd;
+       stream->tracefile_size_current = diff;
+       stream->pos_after_last_complete_data_index = 0;
+       stream->rotate_at_seq_num = -1ULL;
+
+       ret = 0;
+
+end:
+       return ret;
+}
+
+/*
+ * Check if a stream's index file should be rotated (for session rotation).
+ * Must be called with the stream lock held.
+ *
+ * Return 0 on success, a negative value on error.
+ */
+static
+int try_rotate_stream_index(struct relay_stream *stream)
+{
+       int ret = 0;
+
+       if (stream->rotate_at_seq_num == -1ULL) {
+               /* No rotation expected. */
+               goto end;
+       }
+
+       if (stream->index_rotated) {
+               /* Rotation of the index has already occurred. */
+               goto end;
+       }
+
+       if (stream->prev_index_seq == -1ULL ||
+                       stream->prev_index_seq < stream->rotate_at_seq_num) {
+               DBG("Stream %" PRIu64 " index not yet ready for rotation (rotate_at_seq_num = %" PRIu64 ", prev_index_seq = %" PRIu64 ")",
+                               stream->stream_handle,
+                               stream->rotate_at_seq_num,
+                               stream->prev_index_seq);
+               goto end;
+       } else if (stream->prev_index_seq != stream->rotate_at_seq_num) {
+               /*
+                * Unexpected, protocol error/bug.
+                * It could mean that we received a rotation position
+                * that is in the past.
+                */
+               ERR("Stream %" PRIu64 " index is in an inconsistent state (rotate_at_seq_num = %" PRIu64 ", prev_data_seq = %" PRIu64 ", prev_index_seq = %" PRIu64 ")",
+                               stream->stream_handle,
+                               stream->rotate_at_seq_num,
+                               stream->prev_data_seq,
+                               stream->prev_index_seq);
+               ret = -1;
+               goto end;
+       } else {
+               DBG("Rotating stream %" PRIu64 " index file",
+                               stream->stream_handle);
+               ret = create_rotate_index_file(stream, stream->path_name);
+               stream->index_rotated = true;
+
+               if (stream->data_rotated && stream->index_rotated) {
+                       /* Rotation completed; reset its state. */
+                       DBG("Rotation completed for stream %" PRIu64,
+                                       stream->stream_handle);
+                       stream->rotate_at_seq_num = -1ULL;
+                       stream->data_rotated = false;
+                       stream->index_rotated = false;
+               }
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Check if a stream's data file (as opposed to index) should be rotated
+ * (for session rotation).
+ * Must be called with the stream lock held.
+ *
+ * Return 0 on success, a negative value on error.
+ */
+static
+int try_rotate_stream_data(struct relay_stream *stream)
+{
+       int ret = 0;
+
+       if (stream->rotate_at_seq_num == -1ULL) {
+               /* No rotation expected. */
+               goto end;
+       }
+
+       if (stream->data_rotated) {
+               /* Rotation of the data file has already occurred. */
+               goto end;
+       }
+
+       if (stream->prev_data_seq == -1ULL ||
+                       stream->prev_data_seq < stream->rotate_at_seq_num) {
+               DBG("Stream %" PRIu64 " not yet ready for rotation (rotate_at_seq_num = %" PRIu64 ", prev_data_seq = %" PRIu64 ")",
+                               stream->stream_handle,
+                               stream->rotate_at_seq_num,
+                               stream->prev_data_seq);
+               goto end;
+       } else if (stream->prev_data_seq > stream->rotate_at_seq_num) {
+               /*
+                * prev_data_seq is checked here since indexes and rotation
+                * commands are serialized with respect to each other.
+                */
+               DBG("Rotation after too much data has been written in tracefile "
+                               "for stream %" PRIu64 ", need to truncate before "
+                               "rotating", stream->stream_handle);
+               ret = rotate_truncate_stream(stream);
+               if (ret) {
+                       ERR("Failed to truncate stream");
+                       goto end;
                }
+       } else if (stream->prev_data_seq != stream->rotate_at_seq_num) {
+               /*
+                * Unexpected, protocol error/bug.
+                * It could mean that we received a rotation position
+                * that is in the past.
+                */
+               ERR("Stream %" PRIu64 " data is in an inconsistent state (rotate_at_seq_num = %" PRIu64 ", prev_data_seq = %" PRIu64 ")",
+                               stream->stream_handle,
+                               stream->rotate_at_seq_num,
+                               stream->prev_data_seq);
+               ret = -1;
+               goto end;
+       } else {
+               ret = do_rotate_stream_data(stream);
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * relay_recv_metadata: receive the metadata for the session.
+ */
+static int relay_recv_metadata(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       int ret = 0;
+       ssize_t size_ret;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_metadata_payload metadata_payload_header;
+       struct relay_stream *metadata_stream;
+       uint64_t metadata_payload_size;
+
+       if (!session) {
+               ERR("Metadata sent before version check");
+               ret = -1;
+               goto end;
+       }
+
+       if (recv_hdr->data_size < sizeof(struct lttcomm_relayd_metadata_payload)) {
+               ERR("Incorrect data size");
                ret = -1;
                goto end;
        }
-       metadata_struct = (struct lttcomm_relayd_metadata_payload *) data_buffer;
+       metadata_payload_size = recv_hdr->data_size -
+                       sizeof(struct lttcomm_relayd_metadata_payload);
 
-       metadata_stream = stream_get_by_id(be64toh(metadata_struct->stream_id));
+       memcpy(&metadata_payload_header, payload->data,
+                       sizeof(metadata_payload_header));
+       metadata_payload_header.stream_id = be64toh(
+                       metadata_payload_header.stream_id);
+       metadata_payload_header.padding_size = be32toh(
+                       metadata_payload_header.padding_size);
+
+       metadata_stream = stream_get_by_id(metadata_payload_header.stream_id);
        if (!metadata_stream) {
                ret = -1;
                goto end;
@@ -1567,25 +1895,32 @@ static int relay_recv_metadata(struct lttcomm_relayd_hdr *recv_hdr,
 
        pthread_mutex_lock(&metadata_stream->lock);
 
-       size_ret = lttng_write(metadata_stream->stream_fd->fd, metadata_struct->payload,
-                       payload_size);
-       if (size_ret < payload_size) {
+       size_ret = lttng_write(metadata_stream->stream_fd->fd,
+                       payload->data + sizeof(metadata_payload_header),
+                       metadata_payload_size);
+       if (size_ret < metadata_payload_size) {
                ERR("Relay error writing metadata on file");
                ret = -1;
                goto end_put;
        }
 
        size_ret = write_padding_to_file(metadata_stream->stream_fd->fd,
-                       be32toh(metadata_struct->padding_size));
-       if (size_ret < 0) {
+                       metadata_payload_header.padding_size);
+       if (size_ret < (int64_t) metadata_payload_header.padding_size) {
+               ret = -1;
                goto end_put;
        }
 
        metadata_stream->metadata_received +=
-               payload_size + be32toh(metadata_struct->padding_size);
+               metadata_payload_size + metadata_payload_header.padding_size;
        DBG2("Relay metadata written. Updated metadata_received %" PRIu64,
                metadata_stream->metadata_received);
 
+       ret = try_rotate_stream_data(metadata_stream);
+       if (ret < 0) {
+               goto end_put;
+       }
+
 end_put:
        pthread_mutex_unlock(&metadata_stream->lock);
        stream_put(metadata_stream);
@@ -1596,53 +1931,59 @@ end:
 /*
  * relay_send_version: send relayd version number
  */
-static int relay_send_version(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_send_version(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
+       ssize_t send_ret;
        struct lttcomm_relayd_version reply, msg;
        bool compatible = true;
 
-       conn->version_check_done = 1;
+       conn->version_check_done = true;
 
        /* Get version from the other side. */
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < 0 || ret != sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay failed to receive the version values.");
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_send_version\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end;
        }
 
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.major = be32toh(msg.major);
+       msg.minor = be32toh(msg.minor);
+
        memset(&reply, 0, sizeof(reply));
        reply.major = RELAYD_VERSION_COMM_MAJOR;
        reply.minor = RELAYD_VERSION_COMM_MINOR;
 
        /* Major versions must be the same */
-       if (reply.major != be32toh(msg.major)) {
+       if (reply.major != msg.major) {
                DBG("Incompatible major versions (%u vs %u), deleting session",
-                               reply.major, be32toh(msg.major));
+                               reply.major, msg.major);
                compatible = false;
        }
 
        conn->major = reply.major;
        /* We adapt to the lowest compatible version */
-       if (reply.minor <= be32toh(msg.minor)) {
+       if (reply.minor <= msg.minor) {
                conn->minor = reply.minor;
        } else {
-               conn->minor = be32toh(msg.minor);
+               conn->minor = msg.minor;
        }
 
        reply.major = htobe32(reply.major);
        reply.minor = htobe32(reply.minor);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_version), 0);
-       if (ret < 0) {
-               ERR("Relay sending version");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"send version\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+               goto end;
+       } else {
+               ret = 0;
        }
 
        if (!compatible) {
@@ -1660,41 +2001,37 @@ end:
 /*
  * Check for data pending for a given stream id from the session daemon.
  */
-static int relay_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_data_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_data_pending msg;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
+       ssize_t send_ret;
        int ret;
-       uint64_t last_net_seq_num, stream_id;
+       uint64_t stream_seq;
 
        DBG("Data pending command received");
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid data_pending struct size : %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_data_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.stream_id = be64toh(msg.stream_id);
+       msg.last_net_seq_num = be64toh(msg.last_net_seq_num);
 
-       stream_id = be64toh(msg.stream_id);
-       last_net_seq_num = be64toh(msg.last_net_seq_num);
-
-       stream = stream_get_by_id(stream_id);
+       stream = stream_get_by_id(msg.stream_id);
        if (stream == NULL) {
                ret = -1;
                goto end;
@@ -1702,12 +2039,23 @@ static int relay_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
 
        pthread_mutex_lock(&stream->lock);
 
-       DBG("Data pending for stream id %" PRIu64 " prev_seq %" PRIu64
-                       " and last_seq %" PRIu64, stream_id, stream->prev_seq,
-                       last_net_seq_num);
+       if (session_streams_have_index(session)) {
+               /*
+                * Ensure that both the index and stream data have been
+                * flushed up to the requested point.
+                */
+               stream_seq = min(stream->prev_data_seq, stream->prev_index_seq);
+       } else {
+               stream_seq = stream->prev_data_seq;
+       }
+       DBG("Data pending for stream id %" PRIu64 ": prev_data_seq %" PRIu64
+                       ", prev_index_seq %" PRIu64
+                       ", and last_seq %" PRIu64, msg.stream_id,
+                       stream->prev_data_seq, stream->prev_index_seq,
+                       msg.last_net_seq_num);
 
        /* Avoid wrapping issue */
-       if (((int64_t) (stream->prev_seq - last_net_seq_num)) >= 0) {
+       if (((int64_t) (stream_seq - msg.last_net_seq_num)) >= 0) {
                /* Data has in fact been written and is NOT pending */
                ret = 0;
        } else {
@@ -1723,9 +2071,11 @@ end:
 
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(ret);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay data pending ret code failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"data pending\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -1740,52 +2090,53 @@ end_no_session:
  * the control socket has been handled. So, this is why we simply return
  * OK here.
  */
-static int relay_quiescent_control(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_quiescent_control(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
-       uint64_t stream_id;
+       ssize_t send_ret;
        struct relay_stream *stream;
        struct lttcomm_relayd_quiescent_control msg;
        struct lttcomm_relayd_generic_reply reply;
 
        DBG("Checking quiescent state on control socket");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid begin data_pending struct size: %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_quiescent_control\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.stream_id = be64toh(msg.stream_id);
 
-       stream_id = be64toh(msg.stream_id);
-       stream = stream_get_by_id(stream_id);
+       stream = stream_get_by_id(msg.stream_id);
        if (!stream) {
                goto reply;
        }
        pthread_mutex_lock(&stream->lock);
        stream->data_pending_check_done = true;
        pthread_mutex_unlock(&stream->lock);
-       DBG("Relay quiescent control pending flag set to %" PRIu64, stream_id);
+
+       DBG("Relay quiescent control pending flag set to %" PRIu64, msg.stream_id);
        stream_put(stream);
 reply:
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(LTTNG_OK);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay data quiescent control ret code failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"quiescent control\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       } else {
+               ret = 0;
        }
 
 end_no_session:
@@ -1799,41 +2150,36 @@ end_no_session:
  *
  * This command returns to the client a LTTNG_OK code.
  */
-static int relay_begin_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_begin_data_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
+       ssize_t send_ret;
        struct lttng_ht_iter iter;
        struct lttcomm_relayd_begin_data_pending msg;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
-       uint64_t session_id;
 
        assert(recv_hdr);
        assert(conn);
 
        DBG("Init streams for data pending");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid begin data_pending struct size: %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_begin_data_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
-
-       session_id = be64toh(msg.session_id);
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.session_id = be64toh(msg.session_id);
 
        /*
         * Iterate over all streams to set the begin data pending flag.
@@ -1847,7 +2193,7 @@ static int relay_begin_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
                if (!stream_get(stream)) {
                        continue;
                }
-               if (stream->trace->session->id == session_id) {
+               if (stream->trace->session->id == msg.session_id) {
                        pthread_mutex_lock(&stream->lock);
                        stream->data_pending_check_done = false;
                        pthread_mutex_unlock(&stream->lock);
@@ -1862,9 +2208,13 @@ static int relay_begin_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
        /* All good, send back reply. */
        reply.ret_code = htobe32(LTTNG_OK);
 
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay begin data pending send reply failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"begin data pending\" command reply (ret = %zd)",
+                       send_ret);
+               ret = -1;
+       } else {
+               ret = 0;
        }
 
 end_no_session:
@@ -1880,39 +2230,34 @@ end_no_session:
  *
  * Return to the client if there is data in flight or not with a ret_code.
  */
-static int relay_end_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_end_data_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
+       ssize_t send_ret;
        struct lttng_ht_iter iter;
        struct lttcomm_relayd_end_data_pending msg;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
-       uint64_t session_id;
        uint32_t is_data_inflight = 0;
 
        DBG("End data pending command");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid end data_pending struct size: %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_end_data_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
-
-       session_id = be64toh(msg.session_id);
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.session_id = be64toh(msg.session_id);
 
        /*
         * Iterate over all streams to see if the begin data pending
@@ -1924,13 +2269,24 @@ static int relay_end_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
                if (!stream_get(stream)) {
                        continue;
                }
-               if (stream->trace->session->id != session_id) {
+               if (stream->trace->session->id != msg.session_id) {
                        stream_put(stream);
                        continue;
                }
                pthread_mutex_lock(&stream->lock);
                if (!stream->data_pending_check_done) {
-                       if (!stream->closed || !(((int64_t) (stream->prev_seq - stream->last_net_seq_num)) >= 0)) {
+                       uint64_t stream_seq;
+
+                       if (session_streams_have_index(conn->session)) {
+                               /*
+                                * Ensure that both the index and stream data have been
+                                * flushed up to the requested point.
+                                */
+                               stream_seq = min(stream->prev_data_seq, stream->prev_index_seq);
+                       } else {
+                               stream_seq = stream->prev_data_seq;
+                       }
+                       if (!stream->closed || !(((int64_t) (stream_seq - stream->last_net_seq_num)) >= 0)) {
                                is_data_inflight = 1;
                                DBG("Data is still in flight for stream %" PRIu64,
                                                stream->stream_handle);
@@ -1948,9 +2304,13 @@ static int relay_end_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
        /* All good, send back reply. */
        reply.ret_code = htobe32(is_data_inflight);
 
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay end data pending send reply failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"end data pending\" command reply (ret = %zd)",
+                       send_ret);
+               ret = -1;
+       } else {
+               ret = 0;
        }
 
 end_no_session:
@@ -1962,23 +2322,24 @@ end_no_session:
  *
  * Return 0 on success else a negative value.
  */
-static int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_recv_index(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret;
+       int ret;
+       ssize_t send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_index index_info;
        struct relay_index *index;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
-       uint64_t net_seq_num;
        size_t msg_len;
 
        assert(conn);
 
        DBG("Relay receiving index");
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
@@ -1987,22 +2348,29 @@ static int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
        msg_len = lttcomm_relayd_index_len(
                        lttng_to_index_major(conn->major, conn->minor),
                        lttng_to_index_minor(conn->major, conn->minor));
-       ret = conn->sock->ops->recvmsg(conn->sock, &index_info,
-                       msg_len, 0);
-       if (ret < msg_len) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid index struct size : %d", ret);
-               }
+       if (payload->size < msg_len) {
+               ERR("Unexpected payload size in \"relay_recv_index\": expected >= %zu bytes, got %zu bytes",
+                               msg_len, payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&index_info, payload->data, msg_len);
+       index_info.relay_stream_id = be64toh(index_info.relay_stream_id);
+       index_info.net_seq_num = be64toh(index_info.net_seq_num);
+       index_info.packet_size = be64toh(index_info.packet_size);
+       index_info.content_size = be64toh(index_info.content_size);
+       index_info.timestamp_begin = be64toh(index_info.timestamp_begin);
+       index_info.timestamp_end = be64toh(index_info.timestamp_end);
+       index_info.events_discarded = be64toh(index_info.events_discarded);
+       index_info.stream_id = be64toh(index_info.stream_id);
 
-       net_seq_num = be64toh(index_info.net_seq_num);
+       if (conn->minor >= 8) {
+               index_info.stream_instance_id =
+                               be64toh(index_info.stream_instance_id);
+               index_info.packet_seq_num = be64toh(index_info.packet_seq_num);
+       }
 
-       stream = stream_get_by_id(be64toh(index_info.relay_stream_id));
+       stream = stream_get_by_id(index_info.relay_stream_id);
        if (!stream) {
                ERR("stream_get_by_id not found");
                ret = -1;
@@ -2021,8 +2389,7 @@ static int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
                 */
                if (stream->index_received_seqcount > 0
                                && stream->indexes_in_flight == 0) {
-                       stream->beacon_ts_end =
-                               be64toh(index_info.timestamp_end);
+                       stream->beacon_ts_end = index_info.timestamp_end;
                }
                ret = 0;
                goto end_stream_put;
@@ -2031,9 +2398,9 @@ static int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
        }
 
        if (stream->ctf_stream_id == -1ULL) {
-               stream->ctf_stream_id = be64toh(index_info.stream_id);
+               stream->ctf_stream_id = index_info.stream_id;
        }
-       index = relay_index_get_by_id_or_create(stream, net_seq_num);
+       index = relay_index_get_by_id_or_create(stream, index_info.net_seq_num);
        if (!index) {
                ret = -1;
                ERR("relay_index_get_by_id_or_create index NULL");
@@ -2049,12 +2416,24 @@ static int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
        if (ret == 0) {
                tracefile_array_commit_seq(stream->tfa);
                stream->index_received_seqcount++;
+               stream->pos_after_last_complete_data_index += index->total_size;
+               stream->prev_index_seq = index_info.net_seq_num;
+
+               ret = try_rotate_stream_index(stream);
+               if (ret < 0) {
+                       goto end_stream_put;
+               }
        } else if (ret > 0) {
                /* no flush. */
                ret = 0;
        } else {
+               /*
+                * ret < 0
+                *
+                * relay_index_try_flush is responsible for the self-reference
+                * put of the index object on error.
+                */
                ERR("relay_index_try_flush error %d", ret);
-               relay_index_put(index);
                ret = -1;
        }
 
@@ -2071,9 +2450,9 @@ end:
                reply.ret_code = htobe32(LTTNG_OK);
        }
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending close index id reply");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"recv index\" command reply (ret = %zd)", send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -2085,17 +2464,19 @@ end_no_session:
  *
  * Return 0 on success else a negative value.
  */
-static int relay_streams_sent(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_streams_sent(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret;
+       int ret;
+       ssize_t send_ret;
        struct lttcomm_relayd_generic_reply reply;
 
        assert(conn);
 
        DBG("Relay receiving streams_sent");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
@@ -2110,9 +2491,10 @@ static int relay_streams_sent(struct lttcomm_relayd_hdr *recv_hdr,
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(LTTNG_OK);
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending sent_stream reply");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"streams sent\" command reply (ret = %zd)",
+                       send_ret);
+               ret = -1;
        } else {
                /* Success. */
                ret = 0;
@@ -2122,19 +2504,167 @@ end_no_session:
        return ret;
 }
 
+/*
+ * relay_rotate_session_stream: rotate a stream to a new tracefile for the session
+ * rotation feature (not the tracefile rotation feature).
+ */
+static int relay_rotate_session_stream(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       int ret;
+       ssize_t send_ret;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_rotate_stream stream_info;
+       struct lttcomm_relayd_generic_reply reply;
+       struct relay_stream *stream;
+       size_t header_len;
+       size_t path_len;
+       struct lttng_buffer_view new_path_view;
+
+       DBG("Rotate stream received");
+
+       if (!session || !conn->version_check_done) {
+               ERR("Trying to rotate a stream before version check");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       if (session->major == 2 && session->minor < 11) {
+               ERR("Unsupported feature before 2.11");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       header_len = sizeof(struct lttcomm_relayd_rotate_stream);
+
+       if (payload->size < header_len) {
+               ERR("Unexpected payload size in \"relay_rotate_session_stream\": expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       memcpy(&stream_info, payload->data, header_len);
+
+       /* Convert to host */
+       stream_info.pathname_length = be32toh(stream_info.pathname_length);
+       stream_info.stream_id = be64toh(stream_info.stream_id);
+       stream_info.new_chunk_id = be64toh(stream_info.new_chunk_id);
+       stream_info.rotate_at_seq_num = be64toh(stream_info.rotate_at_seq_num);
+
+       path_len = stream_info.pathname_length;
+       if (payload->size < header_len + path_len) {
+               ERR("Unexpected payload size in \"relay_rotate_session_stream\" including path: expected >= %zu bytes, got %zu bytes",
+                               header_len + path_len, payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }       
+       
+       /* Ensure it fits in local filename length. */
+       if (path_len >= LTTNG_PATH_MAX) {
+               ret = -ENAMETOOLONG;
+               ERR("Length of relay_rotate_session_stream command's path name (%zu bytes) exceeds the maximal allowed length of %i bytes",
+                               path_len, LTTNG_PATH_MAX);
+               goto end;
+       }
+
+       new_path_view = lttng_buffer_view_from_view(payload, header_len,
+                       stream_info.pathname_length);
+
+       stream = stream_get_by_id(stream_info.stream_id);
+       if (!stream) {
+               ret = -1;
+               goto end;
+       }
+
+       pthread_mutex_lock(&stream->lock);
+
+       /*
+        * Update the trace path (just the folder, the stream name does not
+        * change).
+        */
+       free(stream->prev_path_name);
+       stream->prev_path_name = stream->path_name;
+       stream->path_name = create_output_path(new_path_view.data);
+       if (!stream->path_name) {
+               ERR("Failed to create a new output path");
+               ret = -1;
+               goto end_stream_unlock;
+       }
+       ret = utils_mkdir_recursive(stream->path_name, S_IRWXU | S_IRWXG,
+                       -1, -1);
+       if (ret < 0) {
+               ERR("relay creating output directory");
+               ret = -1;
+               goto end_stream_unlock;
+       }
+
+       assert(stream->current_chunk_id.is_set);
+       stream->current_chunk_id.value = stream_info.new_chunk_id;
+
+       if (stream->is_metadata) {
+               /*
+                * Metadata streams have no index; consider its rotation
+                * complete.
+                */
+               stream->index_rotated = true;
+               /*
+                * The metadata stream is sent only over the control connection
+                * so we know we have all the data to perform the stream
+                * rotation.
+                */
+               ret = do_rotate_stream_data(stream);
+       } else {
+               stream->rotate_at_seq_num = stream_info.rotate_at_seq_num;
+               ret = try_rotate_stream_data(stream);
+               if (ret < 0) {
+                       goto end_stream_unlock;
+               }
+
+               ret = try_rotate_stream_index(stream);
+               if (ret < 0) {
+                       goto end_stream_unlock;
+               }
+       }
+
+end_stream_unlock:
+       pthread_mutex_unlock(&stream->lock);
+       stream_put(stream);
+end:
+       memset(&reply, 0, sizeof(reply));
+       if (ret < 0) {
+               reply.ret_code = htobe32(LTTNG_ERR_UNK);
+       } else {
+               reply.ret_code = htobe32(LTTNG_OK);
+       }
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(struct lttcomm_relayd_generic_reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"rotate session stream\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       }
+
+end_no_reply:
+       return ret;
+}
+
 /*
  * relay_mkdir: Create a folder on the disk.
  */
-static int relay_mkdir(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_mkdir(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
-       ssize_t network_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_mkdir path_info_header;
-       struct lttcomm_relayd_mkdir *path_info = NULL;
        struct lttcomm_relayd_generic_reply reply;
        char *path = NULL;
+       size_t header_len;
+       ssize_t send_ret;
+       struct lttng_buffer_view path_view;
 
        if (!session || !conn->version_check_done) {
                ERR("Trying to create a directory before version check");
@@ -2152,22 +2682,25 @@ static int relay_mkdir(struct lttcomm_relayd_hdr *recv_hdr,
                goto end_no_session;
        }
 
-       network_ret = conn->sock->ops->recvmsg(conn->sock, &path_info_header,
-                       sizeof(path_info_header), 0);
-       if (network_ret < (ssize_t) sizeof(path_info_header)) {
-               if (network_ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Reception of mkdir command argument length failed with ret = %zi, expected %zu",
-                                       network_ret, sizeof(path_info_header));
-               }
+       header_len = sizeof(path_info_header);
+       if (payload->size < header_len) {
+               ERR("Unexpected payload size in \"relay_mkdir\": expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
                ret = -1;
                goto end_no_session;
        }
 
+       memcpy(&path_info_header, payload->data, header_len);
+
        path_info_header.length = be32toh(path_info_header.length);
 
+       if (payload->size < header_len + path_info_header.length) {
+               ERR("Unexpected payload size in \"relay_mkdir\" including path: expected >= %zu bytes, got %zu bytes",
+                               header_len + path_info_header.length, payload->size);
+               ret = -1;
+               goto end_no_session;
+       }
+
        /* Ensure that it fits in local path length. */
        if (path_info_header.length >= LTTNG_PATH_MAX) {
                ret = -ENAMETOOLONG;
@@ -2176,34 +2709,17 @@ static int relay_mkdir(struct lttcomm_relayd_hdr *recv_hdr,
                goto end;
        }
 
-       path_info = zmalloc(sizeof(path_info_header) + path_info_header.length);
-       if (!path_info) {
-               PERROR("zmalloc of mkdir command path");
-               ret = -1;
-               goto end;
-       }
-
-       network_ret = conn->sock->ops->recvmsg(conn->sock, path_info->path,
-                       path_info_header.length, 0);
-       if (network_ret < (ssize_t) path_info_header.length) {
-               if (network_ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Reception of mkdir path argument failed with ret = %zi, expected %" PRIu32,
-                                       network_ret, path_info_header.length);
-               }
-               ret = -1;
-               goto end_no_session;
-       }
+       path_view = lttng_buffer_view_from_view(payload, header_len,
+                       path_info_header.length);
 
-       path = create_output_path(path_info->path);
+       path = create_output_path(path_view.data);
        if (!path) {
                ERR("Failed to create output path");
                ret = -1;
                goto end;
        }
 
+       DBG("MKDIR command has path \"%s\", changed to \"%s\"", path_view.data, path);
        ret = utils_mkdir_recursive(path, S_IRWXU | S_IRWXG, -1, -1);
        if (ret < 0) {
                ERR("relay creating output directory");
@@ -2219,18 +2735,14 @@ end:
        } else {
                reply.ret_code = htobe32(LTTNG_OK);
        }
-       network_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (network_ret < (ssize_t) sizeof(struct lttcomm_relayd_generic_reply)) {
-               ERR("Failed to send mkdir command status code with ret = %zi, expected %zu",
-                               network_ret,
-                               sizeof(struct lttcomm_relayd_generic_reply));
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"mkdir\" command reply (ret = %zd)", send_ret);
                ret = -1;
        }
 
 end_no_session:
        free(path);
-       free(path_info);
        return ret;
 }
 
@@ -2255,18 +2767,20 @@ static int validate_rotate_rename_path_length(const char *path_type,
  * completed. We are not closing any fd here, just moving the folder, so it
  * works even if data is still in-flight.
  */
-static int relay_rotate_rename(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_rotate_rename(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
-       ssize_t network_ret;
+       ssize_t send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_generic_reply reply;
        struct lttcomm_relayd_rotate_rename header;
-       char *received_paths = NULL;
+       size_t header_len;
        size_t received_paths_size;
-       const char *received_old_path, *received_new_path;
        char *complete_old_path = NULL, *complete_new_path = NULL;
+       struct lttng_buffer_view old_path_view;
+       struct lttng_buffer_view new_path_view;
 
        if (!session || !conn->version_check_done) {
                ERR("Trying to rename a trace folder before version check");
@@ -2280,25 +2794,27 @@ static int relay_rotate_rename(struct lttcomm_relayd_hdr *recv_hdr,
                goto end_no_reply;
        }
 
-       network_ret = conn->sock->ops->recvmsg(conn->sock, &header,
-                       sizeof(header), 0);
-       if (network_ret < (ssize_t) sizeof(header)) {
-               if (network_ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown",
-                                       conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive a valid rotate_rename command header: expected %zu bytes, recvmsg() returned %zi",
-                                       sizeof(header), network_ret);
-               }
+       header_len = sizeof(header);
+       if (payload->size < header_len) {
+               ERR("Unexpected payload size in \"relay_rotate_rename\": expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
                ret = -1;
                goto end_no_reply;
        }
 
+       memcpy(&header, payload->data, header_len);
+
        header.old_path_length = be32toh(header.old_path_length);
        header.new_path_length = be32toh(header.new_path_length);
        received_paths_size = header.old_path_length + header.new_path_length;
 
+       if (payload->size < header_len + received_paths_size) {
+               ERR("Unexpected payload size in \"relay_rotate_rename\" including paths: expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }
+
        /* Ensure the paths don't exceed their allowed size. */
        ret = validate_rotate_rename_path_length("old", header.old_path_length);
        if (ret) {
@@ -2309,56 +2825,41 @@ static int relay_rotate_rename(struct lttcomm_relayd_hdr *recv_hdr,
                goto end;
        }
 
-       received_paths = zmalloc(received_paths_size);
-       if (!received_paths) {
-               PERROR("Could not allocate rotate commands paths reception buffer");
-               ret = -1;
-               goto end;
-       }
-
-       network_ret = conn->sock->ops->recvmsg(conn->sock, received_paths,
-                       received_paths_size, 0);
-       if (network_ret < (ssize_t) received_paths_size) {
-               if (network_ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown",
-                                       conn->sock->fd);
-               } else {
-                       ERR("Relay failed to received rename command paths (%zu bytes): recvmsg() returned %zi",
-                                       received_paths_size, network_ret);
-               }
-               ret = -1;
-               goto end_no_reply;
-       }
+       old_path_view = lttng_buffer_view_from_view(payload, header_len,
+                       header.old_path_length);
+       new_path_view = lttng_buffer_view_from_view(payload,
+                       header_len + header.old_path_length,
+                       header.new_path_length);
 
        /* Validate that both paths received are NULL terminated. */
-       if (received_paths[header.old_path_length - 1] != '\0') {
+       if (old_path_view.data[old_path_view.size - 1] != '\0') {
                ERR("relay_rotate_rename command's \"old\" path is invalid (not NULL terminated)");
                ret = -1;
                goto end;
        }
-       if (received_paths[received_paths_size - 1] != '\0') {
+       if (new_path_view.data[new_path_view.size - 1] != '\0') {
                ERR("relay_rotate_rename command's \"new\" path is invalid (not NULL terminated)");
                ret = -1;
                goto end;
        }
 
-       received_old_path = received_paths;
-       received_new_path = received_paths + header.old_path_length;
-
-       complete_old_path = create_output_path(received_old_path);
+       DBG("ROTATE_RENAME command has argument old path = \"%s\", new_path = \"%s\"",
+                       old_path_view.data, new_path_view.data);
+       complete_old_path = create_output_path(old_path_view.data);
        if (!complete_old_path) {
                ERR("Failed to build old output path in rotate_rename command");
                ret = -1;
                goto end;
        }
 
-       complete_new_path = create_output_path(received_new_path);
+       complete_new_path = create_output_path(new_path_view.data);
        if (!complete_new_path) {
                ERR("Failed to build new output path in rotate_rename command");
                ret = -1;
                goto end;
        }
+       DBG("Expanded ROTATE_RENAME arguments to old path = \"%s\", new_path = \"%s\"",
+                       complete_old_path, complete_new_path);
 
        ret = utils_mkdir_recursive(complete_new_path, S_IRWXU | S_IRWXG,
                        -1, -1);
@@ -2387,77 +2888,208 @@ end:
        } else {
                reply.ret_code = htobe32(LTTNG_OK);
        }
-       network_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (network_ret < sizeof(struct lttcomm_relayd_generic_reply)) {
-               ERR("Relay sending stream id");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < sizeof(reply)) {
+               ERR("Failed to send \"rotate rename\" command reply (ret = %zd)",
+                               send_ret);
                ret = -1;
        }
 
 end_no_reply:
-       free(received_paths);
        free(complete_old_path);
        free(complete_new_path);
        return ret;
 }
 
 /*
- * Process the commands received on the control socket
+ * Check if all the streams in the session have completed the last rotation.
+ * The chunk_id value is used to distinguish the cases where a stream was
+ * closed on the consumerd before the rotation started but it still active on
+ * the relayd, and the case where a stream appeared on the consumerd/relayd
+ * after the last rotation started (in that case, it is already writing in the
+ * new chunk folder).
  */
-static int relay_process_control(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static
+int relay_rotate_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_rotate_pending msg;
+       struct lttcomm_relayd_rotate_pending_reply reply;
+       struct lttng_ht_iter iter;
+       struct relay_stream *stream;
+       int ret = 0;
+       ssize_t send_ret;
+       uint64_t chunk_id;
+        bool rotate_pending = false;
+
+       DBG("Rotate pending command received");
+
+       if (!session || !conn->version_check_done) {
+               ERR("Trying to check for data before version check");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       if (session->major == 2 && session->minor < 11) {
+               ERR("Unsupported feature before 2.11");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_rotate_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       memcpy(&msg, payload->data, sizeof(msg));
+
+       chunk_id = be64toh(msg.chunk_id);
+
+       DBG("Evaluating rotate pending for session \"%s\" and  chunk id %" PRIu64,
+                       session->session_name, chunk_id);
+
+       /*
+        * Iterate over all the streams in the session and check if they are
+        * still waiting for data to perform their rotation.
+        */
+       rcu_read_lock();
+       cds_lfht_for_each_entry(relay_streams_ht->ht, &iter.iter, stream,
+                       node.node) {
+               if (!stream_get(stream)) {
+                       continue;
+               }
+               if (stream->trace->session != session) {
+                       stream_put(stream);
+                       continue;
+               }
+               pthread_mutex_lock(&stream->lock);
+               if (stream->rotate_at_seq_num != -1ULL) {
+                       /* We have not yet performed the rotation. */
+                       rotate_pending = true;
+                       DBG("Stream %" PRIu64 " is still rotating",
+                                       stream->stream_handle);
+               } else if (stream->current_chunk_id.value < chunk_id) {
+                       /*
+                        * Stream closed on the consumer but still active on the
+                        * relay.
+                        */
+                       rotate_pending = true;
+                       DBG("Stream %" PRIu64 " did not exist on the consumer "
+                                       "when the last rotation started, but is"
+                                       "still waiting for data before getting"
+                                       "closed",
+                                       stream->stream_handle);
+               }
+               pthread_mutex_unlock(&stream->lock);
+               stream_put(stream);
+               if (rotate_pending) {
+                       goto send_reply;
+               }
+       }
+
+send_reply:
+       rcu_read_unlock();
+       memset(&reply, 0, sizeof(reply));
+       reply.generic.ret_code = htobe32((uint32_t) LTTNG_OK);
+       reply.is_pending = (uint8_t) !!rotate_pending;
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"rotate pending\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       }
+
+end_no_reply:
+       return ret;
+}
+
+#define DBG_CMD(cmd_name, conn) \
+               DBG3("Processing \"%s\" command for socket %i", cmd_name, conn->sock->fd);
+
+static int relay_process_control_command(struct relay_connection *conn,
+               const struct lttcomm_relayd_hdr *header,
+               const struct lttng_buffer_view *payload)
 {
        int ret = 0;
 
-       switch (be32toh(recv_hdr->cmd)) {
+       switch (header->cmd) {
        case RELAYD_CREATE_SESSION:
-               ret = relay_create_session(recv_hdr, conn);
+               DBG_CMD("RELAYD_CREATE_SESSION", conn);
+               ret = relay_create_session(header, conn, payload);
                break;
        case RELAYD_ADD_STREAM:
-               ret = relay_add_stream(recv_hdr, conn);
+               DBG_CMD("RELAYD_ADD_STREAM", conn);
+               ret = relay_add_stream(header, conn, payload);
                break;
        case RELAYD_START_DATA:
-               ret = relay_start(recv_hdr, conn);
+               DBG_CMD("RELAYD_START_DATA", conn);
+               ret = relay_start(header, conn, payload);
                break;
        case RELAYD_SEND_METADATA:
-               ret = relay_recv_metadata(recv_hdr, conn);
+               DBG_CMD("RELAYD_SEND_METADATA", conn);
+               ret = relay_recv_metadata(header, conn, payload);
                break;
        case RELAYD_VERSION:
-               ret = relay_send_version(recv_hdr, conn);
+               DBG_CMD("RELAYD_VERSION", conn);
+               ret = relay_send_version(header, conn, payload);
                break;
        case RELAYD_CLOSE_STREAM:
-               ret = relay_close_stream(recv_hdr, conn);
+               DBG_CMD("RELAYD_CLOSE_STREAM", conn);
+               ret = relay_close_stream(header, conn, payload);
                break;
        case RELAYD_DATA_PENDING:
-               ret = relay_data_pending(recv_hdr, conn);
+               DBG_CMD("RELAYD_DATA_PENDING", conn);
+               ret = relay_data_pending(header, conn, payload);
                break;
        case RELAYD_QUIESCENT_CONTROL:
-               ret = relay_quiescent_control(recv_hdr, conn);
+               DBG_CMD("RELAYD_QUIESCENT_CONTROL", conn);
+               ret = relay_quiescent_control(header, conn, payload);
                break;
        case RELAYD_BEGIN_DATA_PENDING:
-               ret = relay_begin_data_pending(recv_hdr, conn);
+               DBG_CMD("RELAYD_BEGIN_DATA_PENDING", conn);
+               ret = relay_begin_data_pending(header, conn, payload);
                break;
        case RELAYD_END_DATA_PENDING:
-               ret = relay_end_data_pending(recv_hdr, conn);
+               DBG_CMD("RELAYD_END_DATA_PENDING", conn);
+               ret = relay_end_data_pending(header, conn, payload);
                break;
        case RELAYD_SEND_INDEX:
-               ret = relay_recv_index(recv_hdr, conn);
+               DBG_CMD("RELAYD_SEND_INDEX", conn);
+               ret = relay_recv_index(header, conn, payload);
                break;
        case RELAYD_STREAMS_SENT:
-               ret = relay_streams_sent(recv_hdr, conn);
+               DBG_CMD("RELAYD_STREAMS_SENT", conn);
+               ret = relay_streams_sent(header, conn, payload);
                break;
        case RELAYD_RESET_METADATA:
-               ret = relay_reset_metadata(recv_hdr, conn);
+               DBG_CMD("RELAYD_RESET_METADATA", conn);
+               ret = relay_reset_metadata(header, conn, payload);
+               break;
+       case RELAYD_ROTATE_STREAM:
+               DBG_CMD("RELAYD_ROTATE_STREAM", conn);
+               ret = relay_rotate_session_stream(header, conn, payload);
                break;
        case RELAYD_ROTATE_RENAME:
-               ret = relay_rotate_rename(recv_hdr, conn);
+               DBG_CMD("RELAYD_ROTATE_RENAME", conn);
+               ret = relay_rotate_rename(header, conn, payload);
+               break;
+       case RELAYD_ROTATE_PENDING:
+               DBG_CMD("RELAYD_ROTATE_PENDING", conn);
+               ret = relay_rotate_pending(header, conn, payload);
                break;
        case RELAYD_MKDIR:
-               ret = relay_mkdir(recv_hdr, conn);
+               DBG_CMD("RELAYD_MKDIR", conn);
+               ret = relay_mkdir(header, conn, payload);
                break;
        case RELAYD_UPDATE_SYNC_INFO:
        default:
-               ERR("Received unknown command (%u)", be32toh(recv_hdr->cmd));
+               ERR("Received unknown command (%u)", header->cmd);
                relay_unknown_command(conn);
                ret = -1;
                goto end;
@@ -2467,6 +3099,194 @@ end:
        return ret;
 }
 
+static enum relay_connection_status relay_process_control_receive_payload(
+               struct relay_connection *conn)
+{
+       int ret = 0;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct lttng_dynamic_buffer *reception_buffer =
+                       &conn->protocol.ctrl.reception_buffer;
+       struct ctrl_connection_state_receive_payload *state =
+                       &conn->protocol.ctrl.state.receive_payload;
+       struct lttng_buffer_view payload_view;
+
+       if (state->left_to_receive == 0) {
+               /* Short-circuit for payload-less commands. */
+               goto reception_complete;
+       }
+
+       ret = conn->sock->ops->recvmsg(conn->sock,
+                       reception_buffer->data + state->received,
+                       state->left_to_receive, MSG_DONTWAIT);
+       if (ret < 0) {
+               if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                       PERROR("Unable to receive command payload on sock %d",
+                                       conn->sock->fd);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+               }
+               goto end;
+       } else if (ret == 0) {
+               DBG("Socket %d performed an orderly shutdown (received EOF)", conn->sock->fd);
+               status = RELAY_CONNECTION_STATUS_CLOSED;
+               goto end;
+       }
+
+       assert(ret > 0);
+       assert(ret <= state->left_to_receive);
+
+       state->left_to_receive -= ret;
+       state->received += ret;
+
+       if (state->left_to_receive > 0) {
+               /*
+                * Can't transition to the protocol's next state, wait to
+                * receive the rest of the header.
+                */
+               DBG3("Partial reception of control connection protocol payload (received %" PRIu64 " bytes, %" PRIu64 " bytes left to receive, fd = %i)",
+                               state->received, state->left_to_receive,
+                               conn->sock->fd);
+               goto end;
+       }
+
+reception_complete:
+       DBG("Done receiving control command payload: fd = %i, payload size = %" PRIu64 " bytes",
+                       conn->sock->fd, state->received);
+       /*
+        * The payload required to process the command has been received.
+        * A view to the reception buffer is forwarded to the various
+        * commands and the state of the control is reset on success.
+        *
+        * Commands are responsible for sending their reply to the peer.
+        */
+       payload_view = lttng_buffer_view_from_dynamic_buffer(reception_buffer,
+                       0, -1);
+       ret = relay_process_control_command(conn,
+                       &state->header, &payload_view);
+       if (ret < 0) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       ret = connection_reset_protocol_state(conn);
+       if (ret) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+       }
+end:
+       return status;
+}
+
+static enum relay_connection_status relay_process_control_receive_header(
+               struct relay_connection *conn)
+{
+       int ret = 0;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct lttcomm_relayd_hdr header;
+       struct lttng_dynamic_buffer *reception_buffer =
+                       &conn->protocol.ctrl.reception_buffer;
+       struct ctrl_connection_state_receive_header *state =
+                       &conn->protocol.ctrl.state.receive_header;
+
+       assert(state->left_to_receive != 0);
+
+       ret = conn->sock->ops->recvmsg(conn->sock,
+                       reception_buffer->data + state->received,
+                       state->left_to_receive, MSG_DONTWAIT);
+       if (ret < 0) {
+               if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                       PERROR("Unable to receive control command header on sock %d",
+                                       conn->sock->fd);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+               }
+               goto end;
+       } else if (ret == 0) {
+               DBG("Socket %d performed an orderly shutdown (received EOF)", conn->sock->fd);
+               status = RELAY_CONNECTION_STATUS_CLOSED;
+               goto end;
+       }
+
+       assert(ret > 0);
+       assert(ret <= state->left_to_receive);
+
+       state->left_to_receive -= ret;
+       state->received += ret;
+
+       if (state->left_to_receive > 0) {
+               /*
+                * Can't transition to the protocol's next state, wait to
+                * receive the rest of the header.
+                */
+               DBG3("Partial reception of control connection protocol header (received %" PRIu64 " bytes, %" PRIu64 " bytes left to receive, fd = %i)",
+                               state->received, state->left_to_receive,
+                               conn->sock->fd);
+               goto end;
+       }
+
+       /* Transition to next state: receiving the command's payload. */
+       conn->protocol.ctrl.state_id =
+                       CTRL_CONNECTION_STATE_RECEIVE_PAYLOAD;
+       memcpy(&header, reception_buffer->data, sizeof(header));
+       header.circuit_id = be64toh(header.circuit_id);
+       header.data_size = be64toh(header.data_size);
+       header.cmd = be32toh(header.cmd);
+       header.cmd_version = be32toh(header.cmd_version);
+       memcpy(&conn->protocol.ctrl.state.receive_payload.header,
+                       &header, sizeof(header));
+
+       DBG("Done receiving control command header: fd = %i, cmd = %" PRIu32 ", cmd_version = %" PRIu32 ", payload size = %" PRIu64 " bytes",
+                       conn->sock->fd, header.cmd, header.cmd_version,
+                       header.data_size);
+
+       if (header.data_size > DEFAULT_NETWORK_RELAYD_CTRL_MAX_PAYLOAD_SIZE) {
+               ERR("Command header indicates a payload (%" PRIu64 " bytes) that exceeds the maximal payload size allowed on a control connection.",
+                               header.data_size);
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       conn->protocol.ctrl.state.receive_payload.left_to_receive =
+                       header.data_size;
+       conn->protocol.ctrl.state.receive_payload.received = 0;
+       ret = lttng_dynamic_buffer_set_size(reception_buffer,
+                       header.data_size);
+       if (ret) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       if (header.data_size == 0) {
+               /*
+                * Manually invoke the next state as the poll loop
+                * will not wake-up to allow us to proceed further.
+                */
+               status = relay_process_control_receive_payload(conn);
+       }
+end:
+       return status;
+}
+
+/*
+ * Process the commands received on the control socket
+ */
+static enum relay_connection_status relay_process_control(
+               struct relay_connection *conn)
+{
+       enum relay_connection_status status;
+
+       switch (conn->protocol.ctrl.state_id) {
+       case CTRL_CONNECTION_STATE_RECEIVE_HEADER:
+               status = relay_process_control_receive_header(conn);
+               break;
+       case CTRL_CONNECTION_STATE_RECEIVE_PAYLOAD:
+               status = relay_process_control_receive_payload(conn);
+               break;
+       default:
+               ERR("Unknown control connection protocol state encountered.");
+               abort();
+       }
+
+       return status;
+}
+
 /*
  * Handle index for a data stream.
  *
@@ -2475,7 +3295,7 @@ end:
  * Return 0 on success else a negative value.
  */
 static int handle_index_data(struct relay_stream *stream, uint64_t net_seq_num,
-               int rotate_index)
+               bool rotate_index, bool *flushed, uint64_t total_size)
 {
        int ret = 0;
        uint64_t data_offset;
@@ -2499,23 +3319,36 @@ static int handle_index_data(struct relay_stream *stream, uint64_t net_seq_num,
        }
 
        if (rotate_index || !stream->index_file) {
-               uint32_t major, minor;
-
-               /* Put ref on previous index_file. */
-               if (stream->index_file) {
-                       lttng_index_file_put(stream->index_file);
-                       stream->index_file = NULL;
-               }
-               major = stream->trace->session->major;
-               minor = stream->trace->session->minor;
-               stream->index_file = lttng_index_file_create(stream->path_name,
-                               stream->channel_name,
-                               -1, -1, stream->tracefile_size,
-                               tracefile_array_get_file_index_head(stream->tfa),
-                               lttng_to_index_major(major, minor),
-                               lttng_to_index_minor(major, minor));
-               if (!stream->index_file) {
-                       ret = -1;
+               const char *stream_path;
+
+               /*
+                * The data connection creates the stream's first index file.
+                *
+                * This can happen _after_ a ROTATE_STREAM command. In
+                * other words, the data of the first packet of this stream
+                * can be received after a ROTATE_STREAM command.
+                *
+                * The ROTATE_STREAM command changes the stream's path_name
+                * to point to the "next" chunk. If a rotation is pending for
+                * this stream, as indicated by "rotate_at_seq_num != -1ULL",
+                * it means that we are still receiving data that belongs in the
+                * stream's former path.
+                *
+                * In this very specific case, we must ensure that the index
+                * file is created in the streams's former path,
+                * "prev_path_name".
+                *
+                * All other rotations beyond the first one are not affected
+                * by this problem since the actual rotation operation creates
+                * the new chunk's index file.
+                */
+               stream_path = stream->rotate_at_seq_num == -1ULL ?
+                               stream->path_name:
+                               stream->prev_path_name;
+
+               ret = create_rotate_index_file(stream, stream_path);
+               if (ret < 0) {
+                       ERR("Failed to rotate index");
                        /* Put self-ref for this index due to error. */
                        relay_index_put(index);
                        index = NULL;
@@ -2535,70 +3368,105 @@ static int handle_index_data(struct relay_stream *stream, uint64_t net_seq_num,
        if (ret == 0) {
                tracefile_array_commit_seq(stream->tfa);
                stream->index_received_seqcount++;
+               *flushed = true;
        } else if (ret > 0) {
+               index->total_size = total_size;
                /* No flush. */
                ret = 0;
        } else {
-               /* Put self-ref for this index due to error. */
-               relay_index_put(index);
-               index = NULL;
+               /*
+                * ret < 0
+                *
+                * relay_index_try_flush is responsible for the self-reference
+                * put of the index object on error.
+                */
+               ERR("relay_index_try_flush error %d", ret);
                ret = -1;
        }
 end:
        return ret;
 }
 
-/*
- * relay_process_data: Process the data received on the data socket
- */
-static int relay_process_data(struct relay_connection *conn)
+static enum relay_connection_status relay_process_data_receive_header(
+               struct relay_connection *conn)
 {
-       int ret = 0, rotate_index = 0;
-       ssize_t size_ret;
+       int ret;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct data_connection_state_receive_header *state =
+                       &conn->protocol.data.state.receive_header;
+       struct lttcomm_relayd_data_hdr header;
        struct relay_stream *stream;
-       struct lttcomm_relayd_data_hdr data_hdr;
-       uint64_t stream_id;
-       uint64_t net_seq_num;
-       uint32_t data_size;
-       struct relay_session *session;
-       bool new_stream = false, close_requested = false;
-       size_t chunk_size = RECV_DATA_BUFFER_SIZE;
-       size_t recv_off = 0;
-       char data_buffer[chunk_size];
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &data_hdr,
-                       sizeof(struct lttcomm_relayd_data_hdr), 0);
-       if (ret <= 0) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Unable to receive data header on sock %d", conn->sock->fd);
+       assert(state->left_to_receive != 0);
+
+       ret = conn->sock->ops->recvmsg(conn->sock,
+                       state->header_reception_buffer + state->received,
+                       state->left_to_receive, MSG_DONTWAIT);
+       if (ret < 0) {
+               if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                       PERROR("Unable to receive data header on sock %d", conn->sock->fd);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
                }
-               ret = -1;
+               goto end;
+       } else if (ret == 0) {
+               /* Orderly shutdown. Not necessary to print an error. */
+               DBG("Socket %d performed an orderly shutdown (received EOF)", conn->sock->fd);
+               status = RELAY_CONNECTION_STATUS_CLOSED;
                goto end;
        }
 
-       stream_id = be64toh(data_hdr.stream_id);
-       stream = stream_get_by_id(stream_id);
-       if (!stream) {
-               ERR("relay_process_data: Cannot find stream %" PRIu64, stream_id);
-               ret = -1;
+       assert(ret > 0);
+       assert(ret <= state->left_to_receive);
+
+       state->left_to_receive -= ret;
+       state->received += ret;
+
+       if (state->left_to_receive > 0) {
+               /*
+                * Can't transition to the protocol's next state, wait to
+                * receive the rest of the header.
+                */
+               DBG3("Partial reception of data connection header (received %" PRIu64 " bytes, %" PRIu64 " bytes left to receive, fd = %i)",
+                               state->received, state->left_to_receive,
+                               conn->sock->fd);
                goto end;
        }
-       session = stream->trace->session;
-       data_size = be32toh(data_hdr.data_size);
 
-       net_seq_num = be64toh(data_hdr.net_seq_num);
+       /* Transition to next state: receiving the payload. */
+       conn->protocol.data.state_id = DATA_CONNECTION_STATE_RECEIVE_PAYLOAD;
+
+       memcpy(&header, state->header_reception_buffer, sizeof(header));
+       header.circuit_id = be64toh(header.circuit_id);
+       header.stream_id = be64toh(header.stream_id);
+       header.data_size = be32toh(header.data_size);
+       header.net_seq_num = be64toh(header.net_seq_num);
+       header.padding_size = be32toh(header.padding_size);
+       memcpy(&conn->protocol.data.state.receive_payload.header, &header, sizeof(header));
+
+       conn->protocol.data.state.receive_payload.left_to_receive =
+                       header.data_size;
+       conn->protocol.data.state.receive_payload.received = 0;
+       conn->protocol.data.state.receive_payload.rotate_index = false;
 
-       DBG3("Receiving data of size %u for stream id %" PRIu64 " seqnum %" PRIu64,
-               data_size, stream_id, net_seq_num);
+       DBG("Received data connection header on fd %i: circuit_id = %" PRIu64 ", stream_id = %" PRIu64 ", data_size = %" PRIu32 ", net_seq_num = %" PRIu64 ", padding_size = %" PRIu32,
+                       conn->sock->fd, header.circuit_id,
+                       header.stream_id, header.data_size,
+                       header.net_seq_num, header.padding_size);
+
+       stream = stream_get_by_id(header.stream_id);
+       if (!stream) {
+               DBG("relay_process_data_receive_payload: Cannot find stream %" PRIu64,
+                               header.stream_id);
+               /* Protocol error. */
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
 
        pthread_mutex_lock(&stream->lock);
 
        /* Check if a rotation is needed. */
        if (stream->tracefile_size > 0 &&
-                       (stream->tracefile_size_current + data_size) >
+                       (stream->tracefile_size_current + header.data_size) >
                        stream->tracefile_size) {
                uint64_t old_id, new_id;
 
@@ -2614,77 +3482,185 @@ static int relay_process_data(struct relay_connection *conn)
                                -1, stream->stream_fd->fd,
                                &new_id, &stream->stream_fd->fd);
                if (ret < 0) {
-                       ERR("Rotating stream output file");
+                       ERR("Failed to rotate stream output file");
+                       status = RELAY_CONNECTION_STATUS_ERROR;
                        goto end_stream_unlock;
                }
+
                /*
                 * Reset current size because we just performed a stream
                 * rotation.
                 */
                stream->tracefile_size_current = 0;
-               rotate_index = 1;
+               conn->protocol.data.state.receive_payload.rotate_index = true;
        }
 
-       /*
-        * Index are handled in protocol version 2.4 and above. Also,
-        * snapshot and index are NOT supported.
-        */
-       if (session->minor >= 4 && !session->snapshot) {
-               ret = handle_index_data(stream, net_seq_num, rotate_index);
-               if (ret < 0) {
-                       ERR("handle_index_data: fail stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
-                                       stream->stream_handle, net_seq_num, ret);
+end_stream_unlock:
+       pthread_mutex_unlock(&stream->lock);
+       stream_put(stream);
+end:
+       return status;
+}
+
+static enum relay_connection_status relay_process_data_receive_payload(
+               struct relay_connection *conn)
+{
+       int ret;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct relay_stream *stream;
+       struct data_connection_state_receive_payload *state =
+                       &conn->protocol.data.state.receive_payload;
+       const size_t chunk_size = RECV_DATA_BUFFER_SIZE;
+       char data_buffer[chunk_size];
+       bool partial_recv = false;
+       bool new_stream = false, close_requested = false, index_flushed = false;
+       uint64_t left_to_receive = state->left_to_receive;
+       struct relay_session *session;
+
+       DBG3("Receiving data for stream id %" PRIu64 " seqnum %" PRIu64 ", %" PRIu64" bytes received, %" PRIu64 " bytes left to receive",
+                       state->header.stream_id, state->header.net_seq_num,
+                       state->received, left_to_receive);
+
+       stream = stream_get_by_id(state->header.stream_id);
+       if (!stream) {
+               /* Protocol error. */
+               ERR("relay_process_data_receive_payload: cannot find stream %" PRIu64,
+                               state->header.stream_id);
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       pthread_mutex_lock(&stream->lock);
+       session = stream->trace->session;
+       if (!conn->session) {
+               ret = connection_set_session(conn, session);
+               if (ret) {
+                       status = RELAY_CONNECTION_STATUS_ERROR;
                        goto end_stream_unlock;
                }
        }
 
-       for (recv_off = 0; recv_off < data_size; recv_off += chunk_size) {
-               size_t recv_size = min(data_size - recv_off, chunk_size);
+       /*
+        * The size of the "chunk" received on any iteration is bounded by:
+        *   - the data left to receive,
+        *   - the data immediately available on the socket,
+        *   - the on-stack data buffer
+        */
+       while (left_to_receive > 0 && !partial_recv) {
+               ssize_t write_ret;
+               size_t recv_size = min(left_to_receive, chunk_size);
 
-               ret = conn->sock->ops->recvmsg(conn->sock, data_buffer, recv_size, 0);
-               if (ret <= 0) {
-                       if (ret == 0) {
-                               /* Orderly shutdown. Not necessary to print an error. */
-                               DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-                       } else {
-                               ERR("Socket %d error %d", conn->sock->fd, ret);
+               ret = conn->sock->ops->recvmsg(conn->sock, data_buffer,
+                               recv_size, MSG_DONTWAIT);
+               if (ret < 0) {
+                       if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                               PERROR("Socket %d error", conn->sock->fd);
+                               status = RELAY_CONNECTION_STATUS_ERROR;
                        }
-                       ret = -1;
                        goto end_stream_unlock;
+               } else if (ret == 0) {
+                       /* No more data ready to be consumed on socket. */
+                       DBG3("No more data ready for consumption on data socket of stream id %" PRIu64,
+                                       state->header.stream_id);
+                       status = RELAY_CONNECTION_STATUS_CLOSED;
+                       break;
+               } else if (ret < (int) recv_size) {
+                       /*
+                        * All the data available on the socket has been
+                        * consumed.
+                        */
+                       partial_recv = true;
                }
 
+               recv_size = ret;
+
                /* Write data to stream output fd. */
-               size_ret = lttng_write(stream->stream_fd->fd, data_buffer,
+               write_ret = lttng_write(stream->stream_fd->fd, data_buffer,
                                recv_size);
-               if (size_ret < recv_size) {
+               if (write_ret < (ssize_t) recv_size) {
                        ERR("Relay error writing data to file");
-                       ret = -1;
+                       status = RELAY_CONNECTION_STATUS_ERROR;
                        goto end_stream_unlock;
                }
 
+               left_to_receive -= recv_size;
+               state->received += recv_size;
+               state->left_to_receive = left_to_receive;
+
                DBG2("Relay wrote %zd bytes to tracefile for stream id %" PRIu64,
-                               size_ret, stream->stream_handle);
+                               write_ret, stream->stream_handle);
+       }
+
+       if (state->left_to_receive > 0) {
+               /*
+                * Did not receive all the data expected, wait for more data to
+                * become available on the socket.
+                */
+               DBG3("Partial receive on data connection of stream id %" PRIu64 ", %" PRIu64 " bytes received, %" PRIu64 " bytes left to receive",
+                               state->header.stream_id, state->received,
+                               state->left_to_receive);
+               goto end_stream_unlock;
        }
 
        ret = write_padding_to_file(stream->stream_fd->fd,
-                       be32toh(data_hdr.padding_size));
-       if (ret < 0) {
+                       state->header.padding_size);
+       if ((int64_t) ret < (int64_t) state->header.padding_size) {
                ERR("write_padding_to_file: fail stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
-                               stream->stream_handle, net_seq_num, ret);
+                               stream->stream_handle,
+                               state->header.net_seq_num, ret);
+               status = RELAY_CONNECTION_STATUS_ERROR;
                goto end_stream_unlock;
        }
-       stream->tracefile_size_current +=
-                       data_size + be32toh(data_hdr.padding_size);
-       if (stream->prev_seq == -1ULL) {
+
+
+       if (session_streams_have_index(session)) {
+               ret = handle_index_data(stream, state->header.net_seq_num,
+                               state->rotate_index, &index_flushed, state->header.data_size + state->header.padding_size);
+               if (ret < 0) {
+                       ERR("handle_index_data: fail stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
+                                       stream->stream_handle,
+                                       state->header.net_seq_num, ret);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+                       goto end_stream_unlock;
+               }
+       }
+
+       stream->tracefile_size_current += state->header.data_size +
+                       state->header.padding_size;
+
+       if (stream->prev_data_seq == -1ULL) {
                new_stream = true;
        }
+       if (index_flushed) {
+               stream->pos_after_last_complete_data_index =
+                               stream->tracefile_size_current;
+               stream->prev_index_seq = state->header.net_seq_num;
+               ret = try_rotate_stream_index(stream);
+               if (ret < 0) {
+                       goto end_stream_unlock;
+               }
+       }
+
+       stream->prev_data_seq = state->header.net_seq_num;
 
-       stream->prev_seq = net_seq_num;
+       /*
+        * Resetting the protocol state (to RECEIVE_HEADER) will trash the
+        * contents of *state which are aliased (union) to the same location as
+        * the new state. Don't use it beyond this point.
+        */
+       connection_reset_protocol_state(conn);
+       state = NULL;
+
+       ret = try_rotate_stream_data(stream);
+       if (ret < 0) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end_stream_unlock;
+       }
 
 end_stream_unlock:
        close_requested = stream->close_requested;
        pthread_mutex_unlock(&stream->lock);
-       if (close_requested) {
+       if (close_requested && left_to_receive == 0) {
                try_stream_close(stream);
        }
 
@@ -2693,9 +3669,33 @@ end_stream_unlock:
                uatomic_set(&session->new_streams, 1);
                pthread_mutex_unlock(&session->lock);
        }
+
        stream_put(stream);
 end:
-       return ret;
+       return status;
+}
+
+/*
+ * relay_process_data: Process the data received on the data socket
+ */
+static enum relay_connection_status relay_process_data(
+               struct relay_connection *conn)
+{
+       enum relay_connection_status status;
+
+       switch (conn->protocol.data.state_id) {
+       case DATA_CONNECTION_STATE_RECEIVE_HEADER:
+               status = relay_process_data_receive_header(conn);
+               break;
+       case DATA_CONNECTION_STATE_RECEIVE_PAYLOAD:
+               status = relay_process_data_receive_payload(conn);
+               break;
+       default:
+               ERR("Unexpected data connection communication state.");
+               abort();
+       }
+
+       return status;
 }
 
 static void cleanup_connection_pollfd(struct lttng_poll_event *events, int pollfd)
@@ -2746,7 +3746,6 @@ static void *relay_thread_worker(void *data)
        struct lttng_poll_event events;
        struct lttng_ht *relay_connections_ht;
        struct lttng_ht_iter iter;
-       struct lttcomm_relayd_hdr recv_hdr;
        struct relay_connection *destroy_conn = NULL;
 
        DBG("[thread] Relay worker started");
@@ -2868,21 +3867,36 @@ restart:
                                assert(ctrl_conn->type == RELAY_CONTROL);
 
                                if (revents & LPOLLIN) {
-                                       ret = ctrl_conn->sock->ops->recvmsg(ctrl_conn->sock,
-                                                       &recv_hdr, sizeof(recv_hdr), 0);
-                                       if (ret <= 0) {
-                                               /* Connection closed */
-                                               relay_thread_close_connection(&events, pollfd,
-                                                               ctrl_conn);
-                                       } else {
-                                               ret = relay_process_control(&recv_hdr, ctrl_conn);
-                                               if (ret < 0) {
-                                                       /* Clear the session on error. */
-                                                       relay_thread_close_connection(&events,
-                                                                       pollfd, ctrl_conn);
+                                       enum relay_connection_status status;
+
+                                       status = relay_process_control(ctrl_conn);
+                                       if (status != RELAY_CONNECTION_STATUS_OK) {
+                                               /*
+                                                * On socket error flag the session as aborted to force
+                                                * the cleanup of its stream otherwise it can leak
+                                                * during the lifetime of the relayd.
+                                                *
+                                                * This prevents situations in which streams can be
+                                                * left opened because an index was received, the
+                                                * control connection is closed, and the data
+                                                * connection is closed (uncleanly) before the packet's
+                                                * data provided.
+                                                *
+                                                * Since the control connection encountered an error,
+                                                * it is okay to be conservative and close the
+                                                * session right now as we can't rely on the protocol
+                                                * being respected anymore.
+                                                */
+                                               if (status == RELAY_CONNECTION_STATUS_ERROR) {
+                                                       session_abort(ctrl_conn->session);
                                                }
-                                               seen_control = 1;
+
+                                               /* Clear the connection on error or close. */
+                                               relay_thread_close_connection(&events,
+                                                               pollfd,
+                                                               ctrl_conn);
                                        }
+                                       seen_control = 1;
                                } else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                        relay_thread_close_connection(&events,
                                                        pollfd, ctrl_conn);
@@ -2951,9 +3965,30 @@ restart:
                        assert(data_conn->type == RELAY_DATA);
 
                        if (revents & LPOLLIN) {
-                               ret = relay_process_data(data_conn);
-                               /* Connection closed */
-                               if (ret < 0) {
+                               enum relay_connection_status status;
+
+                               status = relay_process_data(data_conn);
+                               /* Connection closed or error. */
+                               if (status != RELAY_CONNECTION_STATUS_OK) {
+                                       /*
+                                        * On socket error flag the session as aborted to force
+                                        * the cleanup of its stream otherwise it can leak
+                                        * during the lifetime of the relayd.
+                                        *
+                                        * This prevents situations in which streams can be
+                                        * left opened because an index was received, the
+                                        * control connection is closed, and the data
+                                        * connection is closed (uncleanly) before the packet's
+                                        * data provided.
+                                        *
+                                        * Since the data connection encountered an error,
+                                        * it is okay to be conservative and close the
+                                        * session right now as we can't rely on the protocol
+                                        * being respected anymore.
+                                        */
+                                       if (status == RELAY_CONNECTION_STATUS_ERROR) {
+                                               session_abort(data_conn->session);
+                                       }
                                        relay_thread_close_connection(&events, pollfd,
                                                        data_conn);
                                        /*
@@ -2985,16 +4020,14 @@ restart:
 
 exit:
 error:
-       /* Cleanup reamaining connection object. */
+       /* Cleanup remaining connection object. */
        rcu_read_lock();
        cds_lfht_for_each_entry(relay_connections_ht->ht, &iter.iter,
                        destroy_conn,
                        sock_n.node) {
                health_code_update();
 
-               if (session_abort(destroy_conn->session)) {
-                       assert(0);
-               }
+               session_abort(destroy_conn->session);
 
                /*
                 * No need to grab another ref, because we own
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