Fix: uninitialized variable returned by relay_rotate_session_streams
[lttng-tools.git] / src / bin / lttng-relayd / main.c
index 0ee27efce03af5a5dfa7d6f07c8899c001626f10..8fe3dd96deabe322f7e634bbd51aa78ffcfd70d0 100644 (file)
@@ -37,6 +37,7 @@
 #include <inttypes.h>
 #include <urcu/futex.h>
 #include <urcu/uatomic.h>
+#include <urcu/rculist.h>
 #include <unistd.h>
 #include <fcntl.h>
 
@@ -58,7 +59,7 @@
 #include <common/config/session-config.h>
 #include <common/dynamic-buffer.h>
 #include <common/buffer-view.h>
-#include <urcu/rculist.h>
+#include <common/string-utils/format.h>
 
 #include "cmd.h"
 #include "ctf-trace.h"
@@ -74,6 +75,7 @@
 #include "connection.h"
 #include "tracefile-array.h"
 #include "tcp_keep_alive.h"
+#include "sessiond-trace-chunks.h"
 
 static const char *help_msg =
 #ifdef LTTNG_EMBED_HELP
@@ -104,7 +106,6 @@ 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. */
@@ -167,6 +168,8 @@ struct lttng_ht *sessions_ht;
 /* Relayd health monitoring */
 struct health_app *health_relayd;
 
+struct sessiond_trace_chunk_registry *sessiond_trace_chunk_registry;
+
 static struct option long_options[] = {
        { "control-port", 1, 0, 'C', },
        { "data-port", 1, 0, 'D', },
@@ -1048,33 +1051,6 @@ error_testpoint:
        return NULL;
 }
 
-/*
- * Set index data from the control port to a given index object.
- */
-static int set_index_control_data(struct relay_index *index,
-               struct lttcomm_relayd_index *data,
-               struct relay_connection *conn)
-{
-       struct ctf_packet_index index_data;
-
-       /*
-        * The index on disk is encoded in big endian.
-        */
-       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 = 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;
@@ -1092,16 +1068,16 @@ static int relay_create_session(const struct lttcomm_relayd_hdr *recv_hdr,
        int ret = 0;
        ssize_t send_ret;
        struct relay_session *session = NULL;
-       struct lttcomm_relayd_status_session reply;
-       char session_name[LTTNG_NAME_MAX];
-       char hostname[LTTNG_HOST_NAME_MAX];
+       struct lttcomm_relayd_status_session reply = {};
+       char session_name[LTTNG_NAME_MAX] = {};
+       char hostname[LTTNG_HOST_NAME_MAX] = {};
        uint32_t live_timer = 0;
        bool snapshot = false;
-
-       memset(session_name, 0, LTTNG_NAME_MAX);
-       memset(hostname, 0, LTTNG_HOST_NAME_MAX);
-
-       memset(&reply, 0, sizeof(reply));
+       /* Left nil for peers < 2.11. */
+       lttng_uuid sessiond_uuid = {};
+       LTTNG_OPTIONAL(uint64_t) id_sessiond = {};
+       LTTNG_OPTIONAL(uint64_t) current_chunk_id = {};
+       LTTNG_OPTIONAL(time_t) creation_time = {};
 
        if (conn->minor < 4) {
                /* From 2.1 to 2.3 */
@@ -1111,9 +1087,28 @@ static int relay_create_session(const struct lttcomm_relayd_hdr *recv_hdr,
                ret = cmd_create_session_2_4(payload, session_name,
                        hostname, &live_timer, &snapshot);
        } else {
+               bool has_current_chunk;
+               uint64_t current_chunk_id_value;
+               time_t creation_time_value;
+               uint64_t id_sessiond_value;
+
                /* From 2.11 to ... */
-               ret = cmd_create_session_2_11(payload, session_name,
-                       hostname, &live_timer, &snapshot);
+               ret = cmd_create_session_2_11(payload, session_name, hostname,
+                               &live_timer, &snapshot, &id_sessiond_value,
+                               sessiond_uuid, &has_current_chunk,
+                               &current_chunk_id_value, &creation_time_value);
+               if (lttng_uuid_is_nil(sessiond_uuid)) {
+                       /* The nil UUID is reserved for pre-2.11 clients. */
+                       ERR("Illegal nil UUID announced by peer in create session command");
+                       ret = -1;
+                       goto send_reply;
+               }
+               LTTNG_OPTIONAL_SET(&id_sessiond, id_sessiond_value);
+               LTTNG_OPTIONAL_SET(&creation_time, creation_time_value);
+               if (has_current_chunk) {
+                       LTTNG_OPTIONAL_SET(&current_chunk_id,
+                                       current_chunk_id_value);
+               }
        }
 
        if (ret < 0) {
@@ -1121,7 +1116,11 @@ static int relay_create_session(const struct lttcomm_relayd_hdr *recv_hdr,
        }
 
        session = session_create(session_name, hostname, live_timer,
-                       snapshot, conn->major, conn->minor);
+                       snapshot, sessiond_uuid,
+                       id_sessiond.is_set ? &id_sessiond.value : NULL,
+                       current_chunk_id.is_set ? &current_chunk_id.value : NULL,
+                       creation_time.is_set ? &creation_time.value : NULL,
+                       conn->major, conn->minor);
        if (!session) {
                ret = -1;
                goto send_reply;
@@ -1181,6 +1180,34 @@ static void publish_connection_local_streams(struct relay_connection *conn)
        pthread_mutex_unlock(&session->lock);
 }
 
+static int conform_channel_path(char *channel_path)
+{
+       int ret = 0;
+
+       if (strstr("../", channel_path)) {
+               ERR("Refusing channel path as it walks up the path hierarchy: \"%s\"",
+                               channel_path);
+               ret = -1;
+               goto end;
+       }
+
+       if (*channel_path == '/') {
+               const size_t len = strlen(channel_path);
+
+               /*
+                * Channel paths from peers prior to 2.11 are expressed as an
+                * absolute path that is, in reality, relative to the relay
+                * daemon's output directory. Remove the leading slash so it
+                * is correctly interpreted as a relative path later on.
+                *
+                * len (and not len - 1) is used to copy the trailing NULL.
+                */
+               bcopy(channel_path + 1, channel_path, len);
+       }
+end:
+       return ret;
+}
+
 /*
  * relay_add_stream: allocate a new stream for a session
  */
@@ -1197,7 +1224,7 @@ static int relay_add_stream(const 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 };
+       LTTNG_OPTIONAL(uint64_t) stream_chunk_id = {};
 
        if (!session || !conn->version_check_done) {
                ERR("Trying to add a stream before version check");
@@ -1225,6 +1252,10 @@ static int relay_add_stream(const struct lttcomm_relayd_hdr *recv_hdr,
                goto send_reply;
        }
 
+       if (conform_channel_path(path_name)) {
+               goto send_reply;
+       }
+
        trace = ctf_trace_get_by_path_or_create(session, path_name);
        if (!trace) {
                goto send_reply;
@@ -1237,8 +1268,7 @@ static int relay_add_stream(const 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,
-               &stream_chunk_id);
+               channel_name, tracefile_size, tracefile_count);
        path_name = NULL;
        channel_name = NULL;
 
@@ -1418,15 +1448,14 @@ int relay_reset_metadata(const struct lttcomm_relayd_hdr *recv_hdr,
                goto end_unlock;
        }
 
-       ret = utils_rotate_stream_file(stream->path_name, stream->channel_name,
-                       0, 0, -1, -1, stream->stream_fd->fd, NULL,
-                       &stream->stream_fd->fd);
+       ret = stream_reset_file(stream);
        if (ret < 0) {
-               ERR("Failed to rotate metadata file %s of channel %s",
-                               stream->path_name, stream->channel_name);
+               ERR("Failed to reset metadata stream %" PRIu64
+                               ": stream_path = %s, channel = %s",
+                               stream->stream_handle, stream->path_name,
+                               stream->channel_name);
                goto end_unlock;
        }
-
 end_unlock:
        pthread_mutex_unlock(&stream->lock);
        stream_put(stream);
@@ -1497,355 +1526,6 @@ static int relay_start(const struct lttcomm_relayd_hdr *recv_hdr,
        return ret;
 }
 
-/*
- * Append padding to the file pointed by the file descriptor fd.
- */
-static int write_padding_to_file(int fd, uint32_t size)
-{
-       ssize_t ret = 0;
-       char *zeros;
-
-       if (size == 0) {
-               goto end;
-       }
-
-       zeros = zmalloc(size);
-       if (zeros == NULL) {
-               PERROR("zmalloc zeros for padding");
-               ret = -1;
-               goto end;
-       }
-
-       ret = lttng_write(fd, zeros, size);
-       if (ret < size) {
-               PERROR("write padding to file");
-       }
-
-       free(zeros);
-
-end:
-       return ret;
-}
-
-/*
- * Close the current index file if it is open, and create a new one.
- *
- * Return 0 on success, -1 on error.
- */
-static
-int create_rotate_index_file(struct relay_stream *stream,
-               const char *stream_path)
-{
-       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;
-       }
-
-       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;
-       }
-
-       /*
-        * Rewind the current tracefile to the position at which the rotation
-        * should have occurred.
-        */
-       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;
-       }
-
-       /* 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);
-
-               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;
-               }
-
-               pos += count;
-       }
-
-       /* 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.
  */
@@ -1854,11 +1534,11 @@ static int relay_recv_metadata(const struct lttcomm_relayd_hdr *recv_hdr,
                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;
+       struct lttng_buffer_view packet_view;
 
        if (!session) {
                ERR("Metadata sent before version check");
@@ -1887,36 +1567,23 @@ static int relay_recv_metadata(const struct lttcomm_relayd_hdr *recv_hdr,
                goto end;
        }
 
-       pthread_mutex_lock(&metadata_stream->lock);
-
-       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");
+       packet_view = lttng_buffer_view_from_view(payload,
+                       sizeof(metadata_payload_header), metadata_payload_size);
+       if (!packet_view.data) {
+               ERR("Invalid metadata packet length announced by header");
                ret = -1;
                goto end_put;
        }
 
-       size_ret = write_padding_to_file(metadata_stream->stream_fd->fd,
+       pthread_mutex_lock(&metadata_stream->lock);
+       ret = stream_write(metadata_stream, &packet_view,
                        metadata_payload_header.padding_size);
-       if (size_ret < (int64_t) metadata_payload_header.padding_size) {
+       pthread_mutex_unlock(&metadata_stream->lock);
+       if (ret){
                ret = -1;
                goto end_put;
        }
-
-       metadata_stream->metadata_received +=
-               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);
 end:
        return ret;
@@ -2324,7 +1991,6 @@ static int relay_recv_index(const struct lttcomm_relayd_hdr *recv_hdr,
        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;
        size_t msg_len;
@@ -2370,73 +2036,17 @@ static int relay_recv_index(const struct lttcomm_relayd_hdr *recv_hdr,
                ret = -1;
                goto end;
        }
-       pthread_mutex_lock(&stream->lock);
-
-       /* Live beacon handling */
-       if (index_info.packet_size == 0) {
-               DBG("Received live beacon for stream %" PRIu64,
-                               stream->stream_handle);
-
-               /*
-                * Only flag a stream inactive when it has already
-                * received data and no indexes are in flight.
-                */
-               if (stream->index_received_seqcount > 0
-                               && stream->indexes_in_flight == 0) {
-                       stream->beacon_ts_end = index_info.timestamp_end;
-               }
-               ret = 0;
-               goto end_stream_put;
-       } else {
-               stream->beacon_ts_end = -1ULL;
-       }
 
-       if (stream->ctf_stream_id == -1ULL) {
-               stream->ctf_stream_id = index_info.stream_id;
-       }
-       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");
-               goto end_stream_put;
-       }
-       if (set_index_control_data(index, &index_info, conn)) {
-               ERR("set_index_control_data error");
-               relay_index_put(index);
-               ret = -1;
+       pthread_mutex_lock(&stream->lock);
+       ret = stream_add_index(stream, &index_info);
+       pthread_mutex_unlock(&stream->lock);
+       if (ret) {
                goto end_stream_put;
        }
-       ret = relay_index_try_flush(index);
-       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);
-               ret = -1;
-       }
 
 end_stream_put:
-       pthread_mutex_unlock(&stream->lock);
        stream_put(stream);
-
 end:
-
        memset(&reply, 0, sizeof(reply));
        if (ret < 0) {
                reply.ret_code = htobe32(LTTNG_ERR_UNK);
@@ -2499,24 +2109,27 @@ end_no_session:
 }
 
 /*
- * relay_rotate_session_stream: rotate a stream to a new tracefile for the session
- * rotation feature (not the tracefile rotation feature).
+ * 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,
+static int relay_rotate_session_streams(
+               const struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn,
                const struct lttng_buffer_view *payload)
 {
        int ret;
+       uint32_t i;
        ssize_t send_ret;
+       enum lttng_error_code reply_code = LTTNG_ERR_UNK;
        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");
+       struct lttcomm_relayd_rotate_streams rotate_streams;
+       struct lttcomm_relayd_generic_reply reply = {};
+       struct relay_stream *stream = NULL;
+       const size_t header_len = sizeof(struct lttcomm_relayd_rotate_streams);
+       struct lttng_trace_chunk *next_trace_chunk = NULL;
+       struct lttng_buffer_view stream_positions;
+       char chunk_id_buf[MAX_INT_DEC_LEN(uint64_t)];
+       const char *chunk_id_str = "none";
 
        if (!session || !conn->version_check_done) {
                ERR("Trying to rotate a stream before version check");
@@ -2530,8 +2143,6 @@ static int relay_rotate_session_stream(const struct lttcomm_relayd_hdr *recv_hdr
                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);
@@ -2539,99 +2150,100 @@ static int relay_rotate_session_stream(const struct lttcomm_relayd_hdr *recv_hdr
                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);
+       memcpy(&rotate_streams, payload->data, header_len);
 
-       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;
-       }
+       /* Convert header to host endianness. */
+       rotate_streams = (typeof(rotate_streams)) {
+               .stream_count = be32toh(rotate_streams.stream_count),
+               .new_chunk_id = (typeof(rotate_streams.new_chunk_id)) {
+                       .is_set = !!rotate_streams.new_chunk_id.is_set,
+                       .value = be64toh(rotate_streams.new_chunk_id.value),
+               }
+       };
 
-       new_path_view = lttng_buffer_view_from_view(payload, header_len,
-                       stream_info.pathname_length);
+       if (rotate_streams.new_chunk_id.is_set) {
+               /*
+                * Retrieve the trace chunk the stream must transition to. As
+                * per the protocol, this chunk should have been created
+                * before this command is received.
+                */
+               next_trace_chunk = sessiond_trace_chunk_registry_get_chunk(
+                               sessiond_trace_chunk_registry,
+                               session->sessiond_uuid, session->id,
+                               rotate_streams.new_chunk_id.value);
+               if (!next_trace_chunk) {
+                       char uuid_str[UUID_STR_LEN];
+
+                       lttng_uuid_to_str(session->sessiond_uuid, uuid_str);
+                       ERR("Unknown next trace chunk in ROTATE_STREAMS command: sessiond_uuid = {%s}, session_id = %" PRIu64
+                                       ", trace_chunk_id = %" PRIu64,
+                                       uuid_str, session->id,
+                                       rotate_streams.new_chunk_id.value);
+                       reply_code = LTTNG_ERR_INVALID_PROTOCOL;
+                       ret = -1;
+                       goto end;
+               }
 
-       stream = stream_get_by_id(stream_info.stream_id);
-       if (!stream) {
-               ret = -1;
-               goto end;
+               ret = snprintf(chunk_id_buf, sizeof(chunk_id_buf), "%" PRIu64,
+                               rotate_streams.new_chunk_id.value);
+               if (ret < 0 || ret >= sizeof(chunk_id_buf)) {
+                       chunk_id_str = "formatting error";
+               } else {
+                       chunk_id_str = chunk_id_buf;
+               }
        }
 
-       pthread_mutex_lock(&stream->lock);
+       DBG("Rotate %" PRIu32 " streams of session \"%s\" to chunk \"%s\"",
+                       rotate_streams.stream_count, session->session_name,
+                       chunk_id_str);
 
-       /*
-        * 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");
+       stream_positions = lttng_buffer_view_from_view(payload,
+                       sizeof(rotate_streams), -1);
+       if (!stream_positions.data ||
+                       stream_positions.size <
+                                       (rotate_streams.stream_count *
+                                                       sizeof(struct lttcomm_relayd_stream_rotation_position))) {
+               reply_code = LTTNG_ERR_INVALID_PROTOCOL;
                ret = -1;
-               goto end_stream_unlock;
+               goto end;
        }
 
-       assert(stream->current_chunk_id.is_set);
-       stream->current_chunk_id.value = stream_info.new_chunk_id;
+       for (i = 0; i < rotate_streams.stream_count; i++) {
+               struct lttcomm_relayd_stream_rotation_position *position_comm =
+                               &((typeof(position_comm)) stream_positions.data)[i];
+               const struct lttcomm_relayd_stream_rotation_position pos = {
+                       .stream_id = be64toh(position_comm->stream_id),
+                       .rotate_at_seq_num = be64toh(
+                                       position_comm->rotate_at_seq_num),
+               };
 
-       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;
+               stream = stream_get_by_id(pos.stream_id);
+               if (!stream) {
+                       reply_code = LTTNG_ERR_INVALID;
+                       ret = -1;
+                       goto end;
                }
 
-               ret = try_rotate_stream_index(stream);
-               if (ret < 0) {
-                       goto end_stream_unlock;
+               pthread_mutex_lock(&stream->lock);
+               ret = stream_set_pending_rotation(stream, next_trace_chunk,
+                               pos.rotate_at_seq_num);
+               pthread_mutex_unlock(&stream->lock);
+               if (ret) {
+                       reply_code = LTTNG_ERR_FILE_CREATION_ERROR;
+                       goto end;
                }
+
+               stream_put(stream);
+               stream = NULL;
        }
 
-end_stream_unlock:
-       pthread_mutex_unlock(&stream->lock);
-       stream_put(stream);
+       reply_code = LTTNG_OK;
 end:
-       memset(&reply, 0, sizeof(reply));
-       if (ret < 0) {
-               reply.ret_code = htobe32(LTTNG_ERR_UNK);
-       } else {
-               reply.ret_code = htobe32(LTTNG_OK);
+       if (stream) {
+               stream_put(stream);
        }
+
+       reply.ret_code = htobe32((uint32_t) reply_code);
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
                        sizeof(struct lttcomm_relayd_generic_reply), 0);
        if (send_ret < (ssize_t) sizeof(reply)) {
@@ -2640,366 +2252,413 @@ end:
                ret = -1;
        }
 
+       ret = 0;
 end_no_reply:
+       lttng_trace_chunk_put(next_trace_chunk);
+       return ret;
+}
+
+static int init_session_output_directory_handle(struct relay_session *session,
+               struct lttng_directory_handle *handle)
+{
+       int ret;
+       /* hostname/session_name */
+       char *session_directory = NULL;
+       /*
+        * base path + session_directory
+        * e.g. /home/user/lttng-traces/hostname/session_name
+        */
+       char *full_session_path = NULL;
+       char creation_time_str[16];
+       struct tm *timeinfo;
+
+       assert(session->creation_time.is_set);
+       timeinfo = localtime(&session->creation_time.value);
+       if (!timeinfo) {
+               ret = -1;
+               goto end;
+       }
+       strftime(creation_time_str, sizeof(creation_time_str), "%Y%m%d-%H%M%S",
+                       timeinfo);
+
+       pthread_mutex_lock(&session->lock);
+       ret = asprintf(&session_directory, "%s/%s-%s", session->hostname,
+                       session->session_name, creation_time_str);
+       pthread_mutex_unlock(&session->lock);
+       if (ret < 0) {
+               PERROR("Failed to format session directory name");
+               goto end;
+       }
+
+       full_session_path = create_output_path(session_directory);
+       if (!full_session_path) {
+               ret = -1;
+               goto end;
+       }
+
+       ret = utils_mkdir_recursive(
+                       full_session_path, S_IRWXU | S_IRWXG, -1, -1);
+       if (ret) {
+               ERR("Failed to create session output path \"%s\"",
+                               full_session_path);
+               goto end;
+       }
+
+       ret = lttng_directory_handle_init(handle, full_session_path);
+       if (ret) {
+               goto end;
+       }
+end:
+       free(session_directory);
+       free(full_session_path);
        return ret;
 }
 
 /*
- * relay_mkdir: Create a folder on the disk.
+ * relay_create_trace_chunk: create a new trace chunk
  */
-static int relay_mkdir(const struct lttcomm_relayd_hdr *recv_hdr,
+static int relay_create_trace_chunk(const struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn,
                const struct lttng_buffer_view *payload)
 {
-       int ret;
-       struct relay_session *session = conn->session;
-       struct lttcomm_relayd_mkdir path_info_header;
-       struct lttcomm_relayd_generic_reply reply;
-       char *path = NULL;
-       size_t header_len;
+       int ret = 0;
        ssize_t send_ret;
-       struct lttng_buffer_view path_view;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_create_trace_chunk *msg;
+       struct lttcomm_relayd_generic_reply reply = {};
+       struct lttng_buffer_view header_view;
+       struct lttng_buffer_view chunk_name_view;
+       struct lttng_trace_chunk *chunk = NULL, *published_chunk = NULL;
+       enum lttng_error_code reply_code = LTTNG_OK;
+       enum lttng_trace_chunk_status chunk_status;
+       struct lttng_directory_handle session_output;
 
        if (!session || !conn->version_check_done) {
-               ERR("Trying to create a directory before version check");
+               ERR("Trying to create a trace chunk before version check");
                ret = -1;
-               goto end_no_session;
+               goto end_no_reply;
        }
 
        if (session->major == 2 && session->minor < 11) {
-               /*
-                * This client is not supposed to use this command since
-                * it predates its introduction.
-                */
-               ERR("relay_mkdir command is unsupported before LTTng 2.11");
+               ERR("Chunk creation command is unsupported before 2.11");
                ret = -1;
-               goto end_no_session;
+               goto end_no_reply;
        }
 
-       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);
+       header_view = lttng_buffer_view_from_view(payload, 0, sizeof(*msg));
+       if (!header_view.data) {
+               ERR("Failed to receive payload of chunk creation command");
                ret = -1;
-               goto end_no_session;
+               goto end_no_reply;
        }
 
-       memcpy(&path_info_header, payload->data, header_len);
+       /* Convert to host endianness. */
+       msg = (typeof(msg)) header_view.data;
+       msg->chunk_id = be64toh(msg->chunk_id);
+       msg->creation_timestamp = be64toh(msg->creation_timestamp);
+       msg->override_name_length = be32toh(msg->override_name_length);
 
-       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);
+       chunk = lttng_trace_chunk_create(
+                       msg->chunk_id, msg->creation_timestamp);
+       if (!chunk) {
+               ERR("Failed to create trace chunk in trace chunk creation command");
                ret = -1;
-               goto end_no_session;
+               reply_code = LTTNG_ERR_NOMEM;
+               goto end;
        }
 
-       /* Ensure that it fits in local path length. */
-       if (path_info_header.length >= LTTNG_PATH_MAX) {
-               ret = -ENAMETOOLONG;
-               ERR("Path name argument of mkdir command (%" PRIu32 " bytes) exceeds the maximal length allowed (%d bytes)",
-                               path_info_header.length, LTTNG_PATH_MAX);
-               goto end;
+       if (msg->override_name_length) {
+               const char *name;
+
+               chunk_name_view = lttng_buffer_view_from_view(payload,
+                               sizeof(*msg),
+                               msg->override_name_length);
+               name = chunk_name_view.data;
+               if (!name || name[msg->override_name_length - 1]) {
+                       ERR("Failed to receive payload of chunk creation command");
+                       ret = -1;
+                       reply_code = LTTNG_ERR_INVALID;
+                       goto end;
+               }
+
+               chunk_status = lttng_trace_chunk_override_name(
+                               chunk, chunk_name_view.data);
+               switch (chunk_status) {
+               case LTTNG_TRACE_CHUNK_STATUS_OK:
+                       break;
+               case LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT:
+                       ERR("Failed to set the name of new trace chunk in trace chunk creation command (invalid name)");
+                       reply_code = LTTNG_ERR_INVALID;
+                       ret = -1;
+                       goto end;
+               default:
+                       ERR("Failed to set the name of new trace chunk in trace chunk creation command (unknown error)");
+                       reply_code = LTTNG_ERR_UNK;
+                       ret = -1;
+                       goto end;
+               }
        }
 
-       path_view = lttng_buffer_view_from_view(payload, header_len,
-                       path_info_header.length);
+       ret = init_session_output_directory_handle(
+                       conn->session, &session_output);
+       if (ret) {
+               reply_code = LTTNG_ERR_CREATE_DIR_FAIL;
+               goto end;
+       }
 
-       path = create_output_path(path_view.data);
-       if (!path) {
-               ERR("Failed to create output path");
+       chunk_status = lttng_trace_chunk_set_credentials_current_user(chunk);
+       if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+               reply_code = LTTNG_ERR_UNK;
                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");
+       chunk_status = lttng_trace_chunk_set_as_owner(chunk, &session_output);
+       if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+               reply_code = LTTNG_ERR_UNK;
+               ret = -1;
                goto end;
        }
 
-       ret = 0;
+       published_chunk = sessiond_trace_chunk_registry_publish_chunk(
+                       sessiond_trace_chunk_registry,
+                       conn->session->sessiond_uuid,
+                       conn->session->id,
+                       chunk);
+       if (!published_chunk) {
+               char uuid_str[UUID_STR_LEN];
 
-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(reply), 0);
-       if (send_ret < (ssize_t) sizeof(reply)) {
-               ERR("Failed to send \"mkdir\" command reply (ret = %zd)", send_ret);
+               lttng_uuid_to_str(conn->session->sessiond_uuid, uuid_str);
+               ERR("Failed to publish chunk: sessiond_uuid = %s, session_id = %" PRIu64 ", chunk_id = %" PRIu64,
+                               uuid_str,
+                               conn->session->id,
+                               msg->chunk_id);
                ret = -1;
+               reply_code = LTTNG_ERR_NOMEM;
+               goto end;
        }
 
-end_no_session:
-       free(path);
-       return ret;
-}
-
-static int validate_rotate_rename_path_length(const char *path_type,
-               uint32_t path_length)
-{
-       int ret = 0;
-
-       if (path_length > LTTNG_PATH_MAX) {
-               ret = -ENAMETOOLONG;
-               ERR("rotate rename \"%s\" path name length (%" PRIu32 " bytes) exceeds the allowed size of %i bytes",
-                               path_type, path_length, LTTNG_PATH_MAX);
-       } else if (path_length == 0) {
-               ret = -EINVAL;
-               ERR("rotate rename \"%s\" path name has an illegal length of 0", path_type);
+       pthread_mutex_lock(&conn->session->lock);
+       if (conn->session->pending_closure_trace_chunk) {
+               /*
+                * Invalid; this means a second create_trace_chunk command was
+                * received before a close_trace_chunk.
+                */
+               ERR("Invalid trace chunk close command received; a trace chunk is already waiting for a trace chunk close command");
+               reply_code = LTTNG_ERR_INVALID_PROTOCOL;
+               ret = -1;
+               goto end_unlock_session;
        }
+       conn->session->pending_closure_trace_chunk =
+                       conn->session->current_trace_chunk;
+       conn->session->current_trace_chunk = published_chunk;
+       published_chunk = NULL;
+end_unlock_session:
+       pthread_mutex_unlock(&conn->session->lock);
+end:
+       reply.ret_code = htobe32((uint32_t) reply_code);
+       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 \"create trace chunk\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       }
+end_no_reply:
+       lttng_trace_chunk_put(chunk);
+       lttng_trace_chunk_put(published_chunk);
+       lttng_directory_handle_fini(&session_output);
        return ret;
 }
 
 /*
- * relay_rotate_rename: rename the trace folder after a rotation is
- * completed. We are not closing any fd here, just moving the folder, so it
- * works even if data is still in-flight.
+ * relay_close_trace_chunk: close a trace chunk
  */
-static int relay_rotate_rename(const struct lttcomm_relayd_hdr *recv_hdr,
+static int relay_close_trace_chunk(const struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn,
                const struct lttng_buffer_view *payload)
 {
-       int ret;
+       int ret = 0;
        ssize_t send_ret;
        struct relay_session *session = conn->session;
-       struct lttcomm_relayd_generic_reply reply;
-       struct lttcomm_relayd_rotate_rename header;
-       size_t header_len;
-       size_t received_paths_size;
-       char *complete_old_path = NULL, *complete_new_path = NULL;
-       struct lttng_buffer_view old_path_view;
-       struct lttng_buffer_view new_path_view;
+       struct lttcomm_relayd_close_trace_chunk *msg;
+       struct lttcomm_relayd_generic_reply reply = {};
+       struct lttng_buffer_view header_view;
+       struct lttng_trace_chunk *chunk = NULL;
+       enum lttng_error_code reply_code = LTTNG_OK;
+       enum lttng_trace_chunk_status chunk_status;
+       uint64_t chunk_id;
+       LTTNG_OPTIONAL(enum lttng_trace_chunk_command_type) close_command = {};
+       time_t close_timestamp;
 
        if (!session || !conn->version_check_done) {
-               ERR("Trying to rename a trace folder before version check");
+               ERR("Trying to close a trace chunk before version check");
                ret = -1;
                goto end_no_reply;
        }
 
        if (session->major == 2 && session->minor < 11) {
-               ERR("relay_rotate_rename command is unsupported before LTTng 2.11");
+               ERR("Chunk close command is unsupported before 2.11");
                ret = -1;
                goto end_no_reply;
        }
 
-       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);
+       header_view = lttng_buffer_view_from_view(payload, 0, sizeof(*msg));
+       if (!header_view.data) {
+               ERR("Failed to receive payload of chunk close command");
                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) {
-               goto end;
-       }
-       ret = validate_rotate_rename_path_length("new", header.new_path_length);
-       if (ret) {
-               goto end;
-       }
-
-       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 (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 (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;
+       /* Convert to host endianness. */
+       msg = (typeof(msg)) header_view.data;
+       chunk_id = be64toh(msg->chunk_id);
+       close_timestamp = (time_t) be64toh(msg->close_timestamp);
+       close_command = (typeof(close_command)){
+               .value = be32toh(msg->close_command.value),
+               .is_set = msg->close_command.is_set,
+       };
+
+       chunk = sessiond_trace_chunk_registry_get_chunk(
+                       sessiond_trace_chunk_registry,
+                       conn->session->sessiond_uuid,
+                       conn->session->id,
+                       chunk_id);
+       if (!chunk) {
+               char uuid_str[UUID_STR_LEN];
+
+               lttng_uuid_to_str(conn->session->sessiond_uuid, uuid_str);
+               ERR("Failed to find chunk to close: sessiond_uuid = %s, session_id = %" PRIu64 ", chunk_id = %" PRIu64,
+                               uuid_str,
+                               conn->session->id,
+                               msg->chunk_id);
+               ret = -1;
+               reply_code = LTTNG_ERR_NOMEM;
                goto end;
        }
 
-       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");
+       pthread_mutex_lock(&session->lock);
+       if (session->pending_closure_trace_chunk &&
+                       session->pending_closure_trace_chunk != chunk) {
+               ERR("Trace chunk close command for session \"%s\" does not target the trace chunk pending closure",
+                               session->session_name);
+               reply_code = LTTNG_ERR_INVALID_PROTOCOL;
                ret = -1;
-               goto end;
+               goto end_unlock_session;
        }
 
-       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");
+       chunk_status = lttng_trace_chunk_set_close_timestamp(
+                       chunk, close_timestamp);
+       if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+               ERR("Failed to set trace chunk close timestamp");
                ret = -1;
-               goto end;
+               reply_code = LTTNG_ERR_UNK;
+               goto end_unlock_session;
        }
-       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);
-       if (ret < 0) {
-               ERR("Failed to mkdir() rotate_rename's \"new\" output directory at \"%s\"",
-                               complete_new_path);
-               goto end;
+       if (close_command.is_set) {
+               chunk_status = lttng_trace_chunk_set_close_command(
+                               chunk, close_command.value);
+               if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+                       ret = -1;
+                       reply_code = LTTNG_ERR_INVALID;
+                       goto end_unlock_session;
+               }
        }
 
-       /*
-        * If a domain has not yet created its channel, the domain-specific
-        * folder might not exist, but this is not an error.
-        */
-       ret = rename(complete_old_path, complete_new_path);
-       if (ret < 0 && errno != ENOENT) {
-               PERROR("Renaming chunk in rotate_rename command from \"%s\" to \"%s\"",
-                               complete_old_path, complete_new_path);
-               goto end;
+       if (session->current_trace_chunk == chunk) {
+               /*
+                * After a trace chunk close command, no new streams
+                * referencing the chunk may be created. Hence, on the
+                * event that no new trace chunk have been created for
+                * the session, the reference to the current trace chunk
+                * is released in order to allow it to be reclaimed when
+                * the last stream releases its reference to it.
+                */
+               lttng_trace_chunk_put(session->current_trace_chunk);
+               session->current_trace_chunk = NULL;
        }
-       ret = 0;
+       lttng_trace_chunk_put(session->pending_closure_trace_chunk);
+       session->pending_closure_trace_chunk = NULL;
+end_unlock_session:
+       pthread_mutex_unlock(&session->lock);
 
 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(reply), 0);
-       if (send_ret < sizeof(reply)) {
-               ERR("Failed to send \"rotate rename\" command reply (ret = %zd)",
+       reply.ret_code = htobe32((uint32_t) reply_code);
+       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 \"create trace chunk\" command reply (ret = %zd)",
                                send_ret);
                ret = -1;
        }
-
 end_no_reply:
-       free(complete_old_path);
-       free(complete_new_path);
+       lttng_trace_chunk_put(chunk);
        return ret;
 }
 
 /*
- * 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).
+ * relay_trace_chunk_exists: check if a trace chunk exists
  */
-static
-int relay_rotate_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+static int relay_trace_chunk_exists(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;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_trace_chunk_exists *msg;
+       struct lttcomm_relayd_trace_chunk_exists_reply reply = {};
+       struct lttng_buffer_view header_view;
+       struct lttng_trace_chunk *chunk = NULL;
        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");
+               ERR("Trying to close a trace chunk before version check");
                ret = -1;
                goto end_no_reply;
        }
 
        if (session->major == 2 && session->minor < 11) {
-               ERR("Unsupported feature before 2.11");
+               ERR("Chunk close command is unsupported 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);
+       header_view = lttng_buffer_view_from_view(payload, 0, sizeof(*msg));
+       if (!header_view.data) {
+               ERR("Failed to receive payload of chunk close command");
                ret = -1;
                goto end_no_reply;
        }
 
-       memcpy(&msg, payload->data, sizeof(msg));
-
-       chunk_id = be64toh(msg.chunk_id);
+       /* Convert to host endianness. */
+       msg = (typeof(msg)) header_view.data;
+       chunk_id = be64toh(msg->chunk_id);
 
-       DBG("Evaluating rotate pending for session \"%s\" and  chunk id %" PRIu64,
-                       session->session_name, chunk_id);
+       chunk = sessiond_trace_chunk_registry_get_chunk(
+                       sessiond_trace_chunk_registry,
+                       conn->session->sessiond_uuid,
+                       conn->session->id,
+                       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);
+       reply = (typeof(reply)) {
+               .generic.ret_code = htobe32((uint32_t) LTTNG_OK),
+               .trace_chunk_exists = !!chunk,
+       };
+       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)",
+               ERR("Failed to send \"create trace chunk\" command reply (ret = %zd)",
                                send_ret);
                ret = -1;
        }
-
 end_no_reply:
+       lttng_trace_chunk_put(chunk);
        return ret;
 }
 
@@ -3065,21 +2724,21 @@ static int relay_process_control_command(struct relay_connection *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);
+       case RELAYD_ROTATE_STREAMS:
+               DBG_CMD("RELAYD_ROTATE_STREAMS", conn);
+               ret = relay_rotate_session_streams(header, conn, payload);
                break;
-       case RELAYD_ROTATE_RENAME:
-               DBG_CMD("RELAYD_ROTATE_RENAME", conn);
-               ret = relay_rotate_rename(header, conn, payload);
+       case RELAYD_CREATE_TRACE_CHUNK:
+               DBG_CMD("RELAYD_CREATE_TRACE_CHUNK", conn);
+               ret = relay_create_trace_chunk(header, conn, payload);
                break;
-       case RELAYD_ROTATE_PENDING:
-               DBG_CMD("RELAYD_ROTATE_PENDING", conn);
-               ret = relay_rotate_pending(header, conn, payload);
+       case RELAYD_CLOSE_TRACE_CHUNK:
+               DBG_CMD("RELAYD_CLOSE_TRACE_CHUNK", conn);
+               ret = relay_close_trace_chunk(header, conn, payload);
                break;
-       case RELAYD_MKDIR:
-               DBG_CMD("RELAYD_MKDIR", conn);
-               ret = relay_mkdir(header, conn, payload);
+       case RELAYD_TRACE_CHUNK_EXISTS:
+               DBG_CMD("RELAYD_TRACE_CHUNK_EXISTS", conn);
+               ret = relay_trace_chunk_exists(header, conn, payload);
                break;
        case RELAYD_UPDATE_SYNC_INFO:
        default:
@@ -3281,106 +2940,6 @@ static enum relay_connection_status relay_process_control(
        return status;
 }
 
-/*
- * Handle index for a data stream.
- *
- * Called with the stream lock held.
- *
- * Return 0 on success else a negative value.
- */
-static int handle_index_data(struct relay_stream *stream, uint64_t net_seq_num,
-               bool rotate_index, bool *flushed, uint64_t total_size)
-{
-       int ret = 0;
-       uint64_t data_offset;
-       struct relay_index *index;
-
-       /* Get data offset because we are about to update the index. */
-       data_offset = htobe64(stream->tracefile_size_current);
-
-       DBG("handle_index_data: stream %" PRIu64 " net_seq_num %" PRIu64 " data offset %" PRIu64,
-                       stream->stream_handle, net_seq_num, stream->tracefile_size_current);
-
-       /*
-        * Lookup for an existing index for that stream id/sequence
-        * number. If it exists, the control thread has already received the
-        * data for it, thus we need to write it to disk.
-        */
-       index = relay_index_get_by_id_or_create(stream, net_seq_num);
-       if (!index) {
-               ret = -1;
-               goto end;
-       }
-
-       if (rotate_index || !stream->index_file) {
-               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;
-                       goto end;
-               }
-       }
-
-       if (relay_index_set_file(index, stream->index_file, data_offset)) {
-               ret = -1;
-               /* Put self-ref for this index due to error. */
-               relay_index_put(index);
-               index = NULL;
-               goto end;
-       }
-
-       ret = relay_index_try_flush(index);
-       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 {
-               /*
-                * 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;
-}
-
 static enum relay_connection_status relay_process_data_receive_header(
                struct relay_connection *conn)
 {
@@ -3457,40 +3016,17 @@ static enum relay_connection_status relay_process_data_receive_header(
        }
 
        pthread_mutex_lock(&stream->lock);
-
-       /* Check if a rotation is needed. */
-       if (stream->tracefile_size > 0 &&
-                       (stream->tracefile_size_current + header.data_size) >
-                       stream->tracefile_size) {
-               uint64_t old_id, new_id;
-
-               old_id = tracefile_array_get_file_index_head(stream->tfa);
-               tracefile_array_file_rotate(stream->tfa);
-
-               /* new_id is updated by utils_rotate_stream_file. */
-               new_id = old_id;
-
-               ret = utils_rotate_stream_file(stream->path_name,
-                               stream->channel_name, stream->tracefile_size,
-                               stream->tracefile_count, -1,
-                               -1, stream->stream_fd->fd,
-                               &new_id, &stream->stream_fd->fd);
-               if (ret < 0) {
-                       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;
-               conn->protocol.data.state.receive_payload.rotate_index = true;
+       /* Prepare stream for the reception of a new packet. */
+       ret = stream_init_packet(stream, header.data_size,
+                       &conn->protocol.data.state.receive_payload.rotate_index);
+       pthread_mutex_unlock(&stream->lock);
+       if (ret) {
+               ERR("Failed to rotate stream output file");
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end_stream_unlock;
        }
 
 end_stream_unlock:
-       pthread_mutex_unlock(&stream->lock);
        stream_put(stream);
 end:
        return status;
@@ -3541,8 +3077,8 @@ static enum relay_connection_status relay_process_data_receive_payload(
         *   - 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);
+               struct lttng_buffer_view packet_chunk;
 
                ret = conn->sock->ops->recvmsg(conn->sock, data_buffer,
                                recv_size, MSG_DONTWAIT);
@@ -3564,14 +3100,15 @@ static enum relay_connection_status relay_process_data_receive_payload(
                         * consumed.
                         */
                        partial_recv = true;
+                       recv_size = ret;
                }
 
-               recv_size = ret;
+               packet_chunk = lttng_buffer_view_init(data_buffer,
+                               0, recv_size);
+               assert(packet_chunk.data);
 
-               /* Write data to stream output fd. */
-               write_ret = lttng_write(stream->stream_fd->fd, data_buffer,
-                               recv_size);
-               if (write_ret < (ssize_t) recv_size) {
+               ret = stream_write(stream, &packet_chunk, 0);
+               if (ret) {
                        ERR("Relay error writing data to file");
                        status = RELAY_CONNECTION_STATUS_ERROR;
                        goto end_stream_unlock;
@@ -3580,9 +3117,6 @@ static enum relay_connection_status relay_process_data_receive_payload(
                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,
-                               write_ret, stream->stream_handle);
        }
 
        if (state->left_to_receive > 0) {
@@ -3596,22 +3130,18 @@ static enum relay_connection_status relay_process_data_receive_payload(
                goto end_stream_unlock;
        }
 
-       ret = write_padding_to_file(stream->stream_fd->fd,
-                       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,
-                               state->header.net_seq_num, ret);
+       ret = stream_write(stream, NULL, state->header.padding_size);
+       if (ret) {
                status = RELAY_CONNECTION_STATUS_ERROR;
                goto end_stream_unlock;
        }
 
-
        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);
+               ret = stream_update_index(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",
+                       ERR("Failed to update index: stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
                                        stream->stream_handle,
                                        state->header.net_seq_num, ret);
                        status = RELAY_CONNECTION_STATUS_ERROR;
@@ -3619,23 +3149,17 @@ static enum relay_connection_status relay_process_data_receive_payload(
                }
        }
 
-       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;
+       ret = stream_complete_packet(stream, state->header.data_size +
+                       state->header.padding_size, state->header.net_seq_num,
+                       index_flushed);
+       if (ret) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end_stream_unlock;
+       }
 
        /*
         * Resetting the protocol state (to RECEIVE_HEADER) will trash the
@@ -3645,12 +3169,6 @@ static enum relay_connection_status relay_process_data_receive_payload(
        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);
@@ -4116,6 +3634,13 @@ int main(int argc, char **argv)
                }
        }
 
+       sessiond_trace_chunk_registry = sessiond_trace_chunk_registry_create();
+       if (!sessiond_trace_chunk_registry) {
+               ERR("Failed to initialize session daemon trace chunk registry");
+               retval = -1;
+               goto exit_sessiond_trace_chunk_registry;
+       }
+
        /* Initialize thread health monitoring */
        health_relayd = health_app_create(NR_HEALTH_RELAYD_TYPES);
        if (!health_relayd) {
@@ -4265,7 +3790,9 @@ exit_health_quit_pipe:
 
 exit_init_data:
        health_app_destroy(health_relayd);
+       sessiond_trace_chunk_registry_destroy(sessiond_trace_chunk_registry);
 exit_health_app_create:
+exit_sessiond_trace_chunk_registry:
 exit_options:
        /*
         * Wait for all pending call_rcu work to complete before tearing
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