Log a better message when canceling autovacuum.

The old message was at DEBUG2, so typically it didn't show up in the
log at all.  As a result, in most cases where autovacuum was canceled,
the only information that was logged was the table being vacuumed,
with no indication as to what problem caused the cancel.  Crank up
the level to LOG and add some more details to assist with debugging.

Back-patch all the way, per discussion on pgsql-hackers.

diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 327f43bb352925e78bd49b3830973b7f487870e7..1fd8f9bf9a40de763c5d8cb2b154850252531e33 100644 (file)
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -1100,12 +1100,29 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
                                !(autovac_pgxact->vacuumFlags & PROC_VACUUM_FOR_WRAPAROUND))
                        {
                                int                     pid = autovac->pid;
+                               StringInfoData locktagbuf;
+                               StringInfoData logbuf;          /* errdetail for server log */
+
+                               initStringInfo(&locktagbuf);
+                               initStringInfo(&logbuf);
+                               DescribeLockTag(&locktagbuf, &lock->tag);
+                               appendStringInfo(&logbuf,
+                                         _("Process %d waits for %s on %s"),
+                                                MyProcPid,
+                                                GetLockmodeName(lock->tag.locktag_lockmethodid,
+                                                                                lockmode),
+                                                locktagbuf.data);
+
+                               /* release lock as quickly as possible */
+                               LWLockRelease(ProcArrayLock);
 
-                               elog(DEBUG2, "sending cancel to blocking autovacuum PID %d",
-                                        pid);
+                               ereport(LOG,
+                                               (errmsg("sending cancel to blocking autovacuum PID %d",
+                                                       pid),
+                                                errdetail_log("%s", logbuf.data)));
 
-                               /* don't hold the lock across the kill() syscall */
-                               LWLockRelease(ProcArrayLock);
+                               pfree(logbuf.data);
+                               pfree(locktagbuf.data);
 
                                /* send the autovacuum worker Back to Old Kent Road */
                                if (kill(pid, SIGINT) < 0)