Fix relayd: stream index file created in the wrong directory

This fix addresses an issue that can cause a stream's index
file to be created in the wrong trace archive chunk's
directory.

The data connection creates a stream's first index file.

This can happen _after_ a ROTATE_STREAM command. More specifically,
the data of the first packet of a stream can be received after a
ROTATE_STREAM command.

The ROTATE_STREAM command changes the streams path_name to point to
the "next" chunk. If a rotation is pending for a 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 fact, we may have never received any data for this stream at this
point.

In this specific case, we must ensure that the index file is created
in the streams's former path, "prev_path_name", on reception of the
first packet's data on the data connection.

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.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-relayd/main.c b/src/bin/lttng-relayd/main.c
index cbe1a607c36add6e8b320f8f57c13a816a9b3dc5..cf6e01ee0ffd1409269ffc9cfc0f2dc662261d04 100644 (file)
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -1539,7 +1539,8 @@ end:
  * Return 0 on success, -1 on error.
  */
 static
-int create_rotate_index_file(struct relay_stream *stream)
+int create_rotate_index_file(struct relay_stream *stream,
+               const char *stream_path)
 {
        int ret;
        uint32_t major, minor;
@@ -1551,7 +1552,7 @@ int create_rotate_index_file(struct relay_stream *stream)
        }
        major = stream->trace->session->major;
        minor = stream->trace->session->minor;
-       stream->index_file = lttng_index_file_create(stream->path_name,
+       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),
@@ -1587,7 +1588,7 @@ int do_rotate_stream(struct relay_stream *stream)
 
        /* Rotate also the index if the stream is not a metadata stream. */
        if (!stream->is_metadata) {
-               ret = create_rotate_index_file(stream);
+               ret = create_rotate_index_file(stream, stream->path_name);
                if (ret < 0) {
                        ERR("Failed to rotate index file");
                        goto end;
@@ -1709,7 +1710,7 @@ int rotate_truncate_stream(struct relay_stream *stream)
                goto end;
        }
 
-       ret = create_rotate_index_file(stream);
+       ret = create_rotate_index_file(stream, stream->path_name);
        if (ret < 0) {
                ERR("Rotate stream index file");
                goto end;
@@ -2526,7 +2527,8 @@ static int relay_rotate_session_stream(const struct lttcomm_relayd_hdr *recv_hdr
         * Update the trace path (just the folder, the stream name does not
         * change).
         */
-       free(stream->path_name);
+       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");
@@ -3250,7 +3252,34 @@ static int handle_index_data(struct relay_stream *stream, uint64_t net_seq_num,
        }
 
        if (rotate_index || !stream->index_file) {
-               ret = create_rotate_index_file(stream);
+               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. */

diff --git a/src/bin/lttng-relayd/stream.c b/src/bin/lttng-relayd/stream.c
index ac880e7e5ddb053be06500e9604e0f45d07bf203..41d44a58598ff9033dfea8cdd69d44f0a63de75b 100644 (file)
--- a/src/bin/lttng-relayd/stream.c
+++ b/src/bin/lttng-relayd/stream.c
@@ -89,6 +89,7 @@ struct relay_stream *stream_create(struct ctf_trace *trace,
        stream->tracefile_size = tracefile_size;
        stream->tracefile_count = tracefile_count;
        stream->path_name = path_name;
+       stream->prev_path_name = NULL;
        stream->channel_name = channel_name;
        stream->rotate_at_seq_num = -1ULL;
        lttng_ht_node_init_u64(&stream->node, stream->stream_handle);
@@ -255,6 +256,7 @@ static void stream_destroy(struct relay_stream *stream)
                tracefile_array_destroy(stream->tfa);
        }
        free(stream->path_name);
+       free(stream->prev_path_name);
        free(stream->channel_name);
        free(stream);
 }

diff --git a/src/bin/lttng-relayd/stream.h b/src/bin/lttng-relayd/stream.h
index ae75dacc3a061e1d77e16445f1f3d0371baf0db9..dcdacfbb6d3fcbf6c3b88a32a1cf8d2e0fec0d2a 100644 (file)
--- a/src/bin/lttng-relayd/stream.h
+++ b/src/bin/lttng-relayd/stream.h
@@ -65,6 +65,20 @@ struct relay_stream {
        struct lttng_index_file *index_file;
 
        char *path_name;
+       /*
+        * prev_path_name is only used for session rotation support.
+        * It is essentially used to work around the fact that index
+        * files are always created from the 'data' connection.
+        *
+        * Hence, it is possible to receive a ROTATE_STREAM command
+        * which affects the stream's path_name before the creation of
+        * an index file. In this situation, the index file of the
+        * 'previous' chunk would be created in the new destination folder.
+        *
+        * It would then be unlinked when the actual index of the new chunk
+        * is created.
+        */
+       char *prev_path_name;
        char *channel_name;
 
        /* On-disk circular buffer of tracefiles. */

diff --git a/src/common/index/index.c b/src/common/index/index.c
index 12d54e00639e353405ca9e23cd0b1f8ae5014dce..fae1bfd4bcabdd9ba90ee3600733264e581ec7dc 100644 (file)
--- a/src/common/index/index.c
+++ b/src/common/index/index.c
@@ -35,7 +35,7 @@
  *
  * Return allocated struct lttng_index_file, NULL on error.
  */
-struct lttng_index_file *lttng_index_file_create(char *path_name,
+struct lttng_index_file *lttng_index_file_create(const char *path_name,
                char *stream_name, int uid, int gid,
                uint64_t size, uint64_t count, uint32_t major, uint32_t minor)
 {

diff --git a/src/common/index/index.h b/src/common/index/index.h
index 7020936b646b33142f3d2021d5f540bac08f29dd..83e61f6484c25d3210d472170578ef36809ced4f 100644 (file)
--- a/src/common/index/index.h
+++ b/src/common/index/index.h
@@ -37,7 +37,7 @@ struct lttng_index_file {
  * create and open have refcount of 1. Use put to decrement the
  * refcount. Destroys when reaching 0. Use "get" to increment refcount.
  */
-struct lttng_index_file *lttng_index_file_create(char *path_name,
+struct lttng_index_file *lttng_index_file_create(const char *path_name,
                char *stream_name, int uid, int gid, uint64_t size,
                uint64_t count, uint32_t major, uint32_t minor);
 struct lttng_index_file *lttng_index_file_open(const char *path_name,