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 8896f6c2dbb07f616ae84e387ea472a6bd3181db..45e435c31b095fe923777ceb6abc0b605d43762e 100644 (file)
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -998,12 +998,29 @@ 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)