Fix: consumerd: user space metadata not regenerated

[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 6d6690a32161a4cbc24e05157f31407fe9c1df74..6a561b4ca7b3be844c7ae2d306b70b473da9eebb 100644 (file)
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -2430,13 +2430,12 @@ int lttng_ustconsumer_close_wakeup_fd(struct lttng_consumer_stream *stream)
 }
 
 static
-void metadata_stream_reset_cache(struct lttng_consumer_stream *stream)
+void metadata_stream_reset_cache_consumed_position(
+               struct lttng_consumer_stream *stream)
 {
        DBG("Reset metadata cache of session %" PRIu64,
                        stream->chan->session_id);
        stream->ust_metadata_pushed = 0;
-       stream->metadata_version = stream->chan->metadata_cache->version;
-       stream->reset_metadata_flag = 1;
 }
 
 /*
@@ -2452,10 +2451,41 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
        int ret;
 
        pthread_mutex_lock(&stream->chan->metadata_cache->lock);
-       if (stream->chan->metadata_cache->max_offset
-                       == stream->ust_metadata_pushed) {
-               ret = 0;
-               goto end;
+       if (stream->chan->metadata_cache->max_offset ==
+           stream->ust_metadata_pushed) {
+               /*
+                * In the context of a user space metadata channel, a
+                * change in version can be detected in two ways:
+                *   1) During the pre-consume of the `read_subbuffer` loop,
+                *   2) When populating the metadata ring buffer (i.e. here).
+                *
+                * This function is invoked when there is no metadata
+                * available in the ring-buffer. If all data was consumed
+                * up to the size of the metadata cache, there is no metadata
+                * to insert in the ring-buffer.
+                *
+                * However, the metadata version could still have changed (a
+                * regeneration without any new data will yield the same cache
+                * size).
+                *
+                * The cache's version is checked for a version change and the
+                * consumed position is reset if one occurred.
+                *
+                * This check is only necessary for the user space domain as
+                * it has to manage the cache explicitly. If this reset was not
+                * performed, no metadata would be consumed (and no reset would
+                * occur as part of the pre-consume) until the metadata size
+                * exceeded the cache size.
+                */
+               if (stream->metadata_version !=
+                               stream->chan->metadata_cache->version) {
+                       metadata_stream_reset_cache_consumed_position(stream);
+                       consumer_stream_metadata_set_version(stream,
+                                       stream->chan->metadata_cache->version);
+               } else {
+                       ret = 0;
+                       goto end;
+               }
        }
 
        write_len = ustctl_write_one_packet_to_channel(stream->chan->uchan,
@@ -2680,7 +2710,7 @@ static int extract_metadata_subbuffer_info(struct lttng_consumer_stream *stream,
                goto end;
        }
 
-       subbuf->info.metadata.version = stream->chan->metadata_cache->version;
+       subbuf->info.metadata.version = stream->metadata_version;
 
 end:
        return ret;
@@ -2924,7 +2954,7 @@ static int lttng_ustconsumer_set_stream_ops(
                stream->read_subbuffer_ops.extract_subbuffer_info =
                                extract_metadata_subbuffer_info;
                stream->read_subbuffer_ops.reset_metadata =
-                               metadata_stream_reset_cache;
+                               metadata_stream_reset_cache_consumed_position;
                if (stream->chan->is_live) {
                        stream->read_subbuffer_ops.on_sleep = signal_metadata;
                        ret = consumer_stream_enable_metadata_bucketization(