Fix: relayd: live: dispose of zombie viewer metadata stream

[lttng-tools.git] / src / bin / lttng-relayd / live.cpp

diff --git a/src/bin/lttng-relayd/live.cpp b/src/bin/lttng-relayd/live.cpp
index 99037e417c0db58cd76e267383a9f3f7dc1bd068..f1f97f91748b9337c43636d2949cf77b187ed336 100644 (file)
--- a/src/bin/lttng-relayd/live.cpp
+++ b/src/bin/lttng-relayd/live.cpp
@@ -2128,6 +2128,7 @@ static int viewer_get_metadata(struct relay_connection *conn)
        struct lttng_viewer_get_metadata request;
        struct lttng_viewer_metadata_packet reply;
        struct relay_viewer_stream *vstream = nullptr;
+       bool dispose_of_stream = false;
 
        LTTNG_ASSERT(conn);
 
@@ -2156,6 +2157,9 @@ static int viewer_get_metadata(struct relay_connection *conn)
                reply.status = htobe32(LTTNG_VIEWER_METADATA_ERR);
                goto send_reply;
        }
+
+       pthread_mutex_lock(&vstream->stream->trace->session->lock);
+       pthread_mutex_lock(&vstream->stream->trace->lock);
        pthread_mutex_lock(&vstream->stream->lock);
        if (!vstream->stream->is_metadata) {
                ERR("Invalid metadata stream");
@@ -2164,10 +2168,6 @@ static int viewer_get_metadata(struct relay_connection *conn)
 
        if (vstream->metadata_sent >= vstream->stream->metadata_received) {
                /*
-                * The live viewers expect to receive a NO_NEW_METADATA
-                * status before a stream disappears, otherwise they abort the
-                * entire live connection when receiving an error status.
-                *
                 * Clear feature resets the metadata_received to 0 until the
                 * same metadata is received again.
                 */
@@ -2176,20 +2176,7 @@ static int viewer_get_metadata(struct relay_connection *conn)
                 * The live viewer considers a closed 0 byte metadata stream as
                 * an error.
                 */
-               if (vstream->metadata_sent > 0) {
-                       if (vstream->stream->closed && vstream->stream->no_new_metadata_notified) {
-                               /*
-                                * Release ownership for the viewer metadata
-                                * stream. Note that this reference is the
-                                * viewer's reference. The vstream still exists
-                                * until the end of the function as
-                                * viewer_stream_get_by_id() took a reference.
-                                */
-                               viewer_stream_put(vstream);
-                       }
-
-                       vstream->stream->no_new_metadata_notified = true;
-               }
+               dispose_of_stream = vstream->metadata_sent > 0 && vstream->stream->closed;
                goto send_reply;
        }
 
@@ -2227,6 +2214,19 @@ static int viewer_get_metadata(struct relay_connection *conn)
        len = vstream->stream->metadata_received - vstream->metadata_sent;
 
        if (!vstream->stream_file.trace_chunk) {
+               if (vstream->stream->trace->session->connection_closed) {
+                       /*
+                        * If the connection is closed, there is no way for the metadata stream
+                        * to ever transition back to an active chunk. As such, signal to the viewer
+                        * that there is no new metadata available.
+                        *
+                        * The stream can be disposed-of. On the next execution of this command,
+                        * the relay daemon will reply with an error status since the stream can't
+                        * be found.
+                        */
+                       dispose_of_stream = true;
+               }
+
                reply.status = htobe32(LTTNG_VIEWER_NO_NEW_METADATA);
                len = 0;
                goto send_reply;
@@ -2357,6 +2357,8 @@ send_reply:
        health_code_update();
        if (vstream) {
                pthread_mutex_unlock(&vstream->stream->lock);
+               pthread_mutex_unlock(&vstream->stream->trace->lock);
+               pthread_mutex_unlock(&vstream->stream->trace->session->lock);
        }
        ret = send_response(conn->sock, &reply, sizeof(reply));
        if (ret < 0) {
@@ -2382,7 +2384,22 @@ end_free:
 end:
        if (vstream) {
                viewer_stream_put(vstream);
+               if (dispose_of_stream) {
+                       /*
+                        * Trigger the destruction of the viewer stream
+                        * by releasing its global reference.
+                        *
+                        * The live viewers expect to receive a NO_NEW_METADATA
+                        * status before a stream disappears, otherwise they abort the
+                        * entire live connection when receiving an error status.
+                        *
+                        * On the next query for this stream, an error will be reported to the
+                        * client.
+                        */
+                       viewer_stream_put(vstream);
+               }
        }
+
        return ret;
 }