Fix: take index seq number into account for rotation pending check
authorJérémie Galarneau <jeremie.galarneau@efficios.com>
Fri, 12 Oct 2018 22:31:51 +0000 (18:31 -0400)
committerJérémie Galarneau <jeremie.galarneau@efficios.com>
Fri, 12 Oct 2018 23:58:11 +0000 (19:58 -0400)
The rotation pending check is only performed on the sequence number of
the received data. However, it is expected that the index of the
stream has been written to disk by the time this check returns that
no rotation is pending.

This patch ensures that the minimum between the data and index
sequence numbers are used to perform this check.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
src/bin/lttng-relayd/main.c

index c84ebaac1c2c66b3d6f282aa6e1d69d161e16f23..f111b931c7792c3b3f627977bb7ed62e6999c1a4 100644 (file)
@@ -1746,18 +1746,27 @@ static
 int try_rotate_stream(struct relay_stream *stream)
 {
        int ret = 0;
+       uint64_t trace_seq;
 
        /* No rotation expected. */
        if (stream->rotate_at_seq_num == -1ULL) {
                goto end;
        }
 
-       if (stream->prev_seq < stream->rotate_at_seq_num ||
-                       stream->prev_seq == -1ULL) {
-               DBG("Stream %" PRIu64 " no yet ready for rotation",
-                               stream->stream_handle);
+       trace_seq = min(stream->prev_seq, stream->prev_index_seq);
+       if (stream->prev_seq == -1ULL || stream->prev_index_seq == -1ULL ||
+                       trace_seq < stream->rotate_at_seq_num) {
+               DBG("Stream %" PRIu64 " not yet ready for rotation (rotate_at_seq_num = %" PRIu64 ", prev_seq = %" PRIu64 ", prev_index_seq = %" PRIu64 ")",
+                               stream->stream_handle,
+                               stream->rotate_at_seq_num,
+                               stream->prev_seq,
+                               stream->prev_index_seq);
                goto end;
        } else if (stream->prev_seq > stream->rotate_at_seq_num) {
+               /*
+                * prev_seq is checked here since indexes and rotation
+                * commands are serialized with respect to each other.
+                */
                DBG("Rotation after too much data has been written in tracefile "
                                "for stream %" PRIu64 ", need to truncate before "
                                "rotating", stream->stream_handle);
@@ -1767,7 +1776,20 @@ int try_rotate_stream(struct relay_stream *stream)
                        goto end;
                }
        } else {
-               /* stream->prev_seq == stream->rotate_at_seq_num */
+               if (trace_seq != stream->rotate_at_seq_num) {
+                       /*
+                        * Unexpected, protocol error/bug.
+                        * It could mean that we received a rotation position
+                        * that is in the past.
+                        */
+                       ERR("Stream %" PRIu64 " is in an inconsistent state (rotate_at_seq_num = %" PRIu64 ", prev_seq = %" PRIu64 ", prev_index_seq = %" PRIu64 ")",
+                               stream->stream_handle,
+                               stream->rotate_at_seq_num,
+                               stream->prev_seq,
+                               stream->prev_index_seq);
+                       ret = -1;
+                       goto end;
+               }
                DBG("Stream %" PRIu64 " ready for rotation",
                                stream->stream_handle);
                ret = do_rotate_stream(stream);
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