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 6ea2fed0b8ea078e580af9ff825c57c63294356c..ffab85f665e8941a3f45f27358e5ae0010596e20 100644 (file)
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -1033,12 +1033,29 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
                                !(autovac->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)