X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fbin%2Flttng-relayd%2Fsessiond-trace-chunks.h;h=2c771d8094fe172628bd41b8ecea38af7dca2bdd;hb=4878de5c7deb512bbdac4fdfc498907efa06fb7c;hp=39804679c811e7306be044faaecec7b579a7db0d;hpb=0c1b0f77482b0d1856fefabc42978b82b5dd267c;p=lttng-tools.git

diff --git a/src/bin/lttng-relayd/sessiond-trace-chunks.h b/src/bin/lttng-relayd/sessiond-trace-chunks.h
index 39804679c..2c771d809 100644
--- a/src/bin/lttng-relayd/sessiond-trace-chunks.h
+++ b/src/bin/lttng-relayd/sessiond-trace-chunks.h
@@ -1,27 +1,28 @@
 /*
- * Copyright (C) 2019 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ * Copyright (C) 2019 Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License, version 2 only, as
- * published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along with
- * this program; if not, write to the Free Software Foundation, Inc., 51
- * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #ifndef SESSIOND_TRACE_CHUNK_REGISTRY_H
 #define SESSIOND_TRACE_CHUNK_REGISTRY_H
 
-#include <common/compat/uuid.h>
+#include <common/uuid.h>
 #include <common/trace-chunk.h>
 #include <stdint.h>
 
+/*
+ * A session trace chunk registry allows the relay daemon to share trace chunks
+ * used by different "relay sessions" when they were created for the same
+ * user-visible session daemon session. Tracing multiple domains (e.g. ust and
+ * kernel) results in per-domain relay sessions being created.
+ *
+ * Sharing trace chunks, and their output directory more specifically, is
+ * essential to properly implement session rotations. The sharing of output
+ * directory handles allows directory renames to be performed once and without
+ * races that would stem from from multiple renames.
+ */
 struct sessiond_trace_chunk_registry;
 
 struct sessiond_trace_chunk_registry *
@@ -55,4 +56,9 @@ sessiond_trace_chunk_registry_get_chunk(
 		const lttng_uuid sessiond_uuid,
 		uint64_t session_id, uint64_t chunk_id);
 
+int sessiond_trace_chunk_registry_chunk_exists(
+		struct sessiond_trace_chunk_registry *sessiond_registry,
+		const lttng_uuid sessiond_uuid,
+		uint64_t session_id, uint64_t chunk_id, bool *chunk_exists);
+
 #endif /* SESSIOND_TRACE_CHUNK_REGISTRY_H */