return start_pos;
}
+/* Stream lock must be held by the caller. */
+static int sample_stream_positions(struct lttng_consumer_stream *stream,
+ unsigned long *produced, unsigned long *consumed)
+{
+ int ret;
+
+ ASSERT_LOCKED(stream->lock);
+
+ ret = lttng_consumer_sample_snapshot_positions(stream);
+ if (ret < 0) {
+ ERR("Failed to sample snapshot positions");
+ goto end;
+ }
+
+ ret = lttng_consumer_get_produced_snapshot(stream, produced);
+ if (ret < 0) {
+ ERR("Failed to sample produced position");
+ goto end;
+ }
+
+ ret = lttng_consumer_get_consumed_snapshot(stream, consumed);
+ if (ret < 0) {
+ ERR("Failed to sample consumed position");
+ goto end;
+ }
+
+end:
+ return ret;
+}
+
/*
* Sample the rotate position for all the streams of a channel. If a stream
* is already at the rotate position (produced == consumed), we flag it as
}
/*
- * Do not flush an empty packet when rotating from a NULL trace
+ * Do not flush a packet when rotating from a NULL trace
* chunk. The stream has no means to output data, and the prior
- * rotation which rotated to NULL performed that side-effect already.
+ * rotation which rotated to NULL performed that side-effect
+ * already. No new data can be produced when a stream has no
+ * associated trace chunk (e.g. a stop followed by a rotate).
*/
if (stream->trace_chunk) {
+ bool flush_active;
+
+ if (stream->metadata_flag) {
+ /*
+ * Don't produce an empty metadata packet,
+ * simply close the current one.
+ *
+ * Metadata is regenerated on every trace chunk
+ * switch; there is no concern that no data was
+ * produced.
+ */
+ flush_active = true;
+ } else {
+ /*
+ * Only flush an empty packet if the "packet
+ * open" could not be performed on transition
+ * to a new trace chunk and no packets were
+ * consumed within the chunk's lifetime.
+ */
+ if (stream->opened_packet_in_current_trace_chunk) {
+ flush_active = true;
+ } else {
+ /*
+ * Stream could have been full at the
+ * time of rotation, but then have had
+ * no activity at all.
+ *
+ * It is important to flush a packet
+ * to prevent 0-length files from being
+ * produced as most viewers choke on
+ * them.
+ *
+ * Unfortunately viewers will not be
+ * able to know that tracing was active
+ * for this stream during this trace
+ * chunk's lifetime.
+ */
+ ret = sample_stream_positions(stream, &produced_pos, &consumed_pos);
+ if (ret) {
+ goto end_unlock_stream;
+ }
+
+ /*
+ * Don't flush an empty packet if data
+ * was produced; it will be consumed
+ * before the rotation completes.
+ */
+ flush_active = produced_pos != consumed_pos;
+ if (!flush_active) {
+ enum lttng_trace_chunk_status chunk_status;
+ const char *trace_chunk_name;
+ uint64_t trace_chunk_id;
+
+ chunk_status = lttng_trace_chunk_get_name(
+ stream->trace_chunk,
+ &trace_chunk_name,
+ NULL);
+ if (chunk_status == LTTNG_TRACE_CHUNK_STATUS_NONE) {
+ trace_chunk_name = "none";
+ }
+
+ /*
+ * Consumer trace chunks are
+ * never anonymous.
+ */
+ chunk_status = lttng_trace_chunk_get_id(
+ stream->trace_chunk,
+ &trace_chunk_id);
+ assert(chunk_status ==
+ LTTNG_TRACE_CHUNK_STATUS_OK);
+
+ DBG("Unable to open packet for stream during trace chunk's lifetime. "
+ "Flushing an empty packet to prevent an empty file from being created: "
+ "stream id = %" PRIu64 ", trace chunk name = `%s`, trace chunk id = %" PRIu64,
+ stream->key, trace_chunk_name, trace_chunk_id);
+ }
+ }
+ }
+
/*
- * For metadata stream, do an active flush, which does not
- * produce empty packets. For data streams, empty-flush;
- * ensures we have at least one packet in each stream per trace
- * chunk, even if no data was produced.
+ * Close the current packet before sampling the
+ * ring buffer positions.
*/
- ret = consumer_stream_flush_buffer(
- stream, stream->metadata_flag ? 1 : 0);
+ ret = consumer_stream_flush_buffer(stream, flush_active);
if (ret < 0) {
ERR("Failed to flush stream %" PRIu64 " during channel rotation",
stream->key);
projects / lttng-tools.git / blobdiff