Add some logging code for unexpected cases in pgstat.c, particularly being

unable to read a stats file for reasons other than ENOENT, and having to reset
last_statrequest because it's later than current time in the collector.
Not clear if this will shed any light on the "pgstat wait timeout" business,
but it seems like a good idea in general.

In passing, do some message-style-police work on recently-added
pgstat_reset_shared_counters code.

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 0d7f629..c00b87c 100644 (file)
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -13,7 +13,7 @@
  *
  *     Copyright (c) 2001-2010, PostgreSQL Global Development Group
  *
- *     $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.201 2010/02/26 02:00:55 momjian Exp $
+ *     $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.202 2010/03/12 22:19:19 tgl Exp $
  * ----------
  */
 #include "postgres.h"
@@ -1177,12 +1177,10 @@ pgstat_reset_shared_counters(const char *target)
        if (strcmp(target, "bgwriter") == 0)
                msg.m_resettarget = RESET_BGWRITER;
        else
-       {
                ereport(ERROR,
-                               (errcode(ERRCODE_SYNTAX_ERROR),
-                                errmsg("unrecognized reset target: '%s'", target),
-                                errhint("allowed targets are 'bgwriter'.")));
-       }
+                               (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                                errmsg("unrecognized reset target: \"%s\"", target),
+                                errhint("Target must be \"bgwriter\".")));
 
        pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSHAREDCOUNTER);
        pgstat_send(&msg, sizeof(msg));
@@ -3292,11 +3290,15 @@ pgstat_write_statsfile(bool permanent)
                /*
                 * It's not entirely clear whether there could be clock skew between
                 * backends and the collector; but just in case someone manages to
-                * send us a stats request time that's far in the future, reset it.
+                * send us a stats request time that's in the future, reset it.
                 * This ensures that no inquiry message can cause more than one stats
                 * file write to occur.
                 */
-               last_statrequest = last_statwrite;
+               if (last_statrequest > last_statwrite)
+               {
+                       elog(LOG, "last_statrequest is in the future, resetting");
+                       last_statrequest = last_statwrite;
+               }
        }
 
        if (permanent)
@@ -3355,9 +3357,20 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
         * Try to open the status file. If it doesn't exist, the backends simply
         * return zero for anything and the collector simply starts from scratch
         * with empty counters.
+        *
+        * ENOENT is a possibility if the stats collector is not running or has
+        * not yet written the stats file the first time.  Any other failure
+        * condition is suspicious.
         */
        if ((fpin = AllocateFile(statfile, PG_BINARY_R)) == NULL)
+       {
+               if (errno != ENOENT)
+                       ereport(pgStatRunningInCollector ? LOG : WARNING,
+                                       (errcode_for_file_access(),
+                                        errmsg("could not open statistics file \"%s\": %m",
+                                                       statfile)));
                return dbhash;
+       }
 
        /*
         * Verify it's of the expected format.
@@ -3366,7 +3379,7 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
                || format_id != PGSTAT_FILE_FORMAT_ID)
        {
                ereport(pgStatRunningInCollector ? LOG : WARNING,
-                               (errmsg("corrupted pgstat.stat file")));
+                               (errmsg("corrupted statistics file \"%s\"", statfile)));
                goto done;
        }
 
@@ -3376,7 +3389,7 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
        if (fread(&globalStats, 1, sizeof(globalStats), fpin) != sizeof(globalStats))
        {
                ereport(pgStatRunningInCollector ? LOG : WARNING,
-                               (errmsg("corrupted pgstat.stat file")));
+                               (errmsg("corrupted statistics file \"%s\"", statfile)));
                goto done;
        }
 
@@ -3398,7 +3411,8 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
                                                  fpin) != offsetof(PgStat_StatDBEntry, tables))
                                {
                                        ereport(pgStatRunningInCollector ? LOG : WARNING,
-                                                       (errmsg("corrupted pgstat.stat file")));
+                                                       (errmsg("corrupted statistics file \"%s\"",
+                                                                       statfile)));
                                        goto done;
                                }
 
@@ -3412,7 +3426,8 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
                                if (found)
                                {
                                        ereport(pgStatRunningInCollector ? LOG : WARNING,
-                                                       (errmsg("corrupted pgstat.stat file")));
+                                                       (errmsg("corrupted statistics file \"%s\"",
+                                                                       statfile)));
                                        goto done;
                                }
 
@@ -3474,7 +3489,8 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
                                                  fpin) != sizeof(PgStat_StatTabEntry))
                                {
                                        ereport(pgStatRunningInCollector ? LOG : WARNING,
-                                                       (errmsg("corrupted pgstat.stat file")));
+                                                       (errmsg("corrupted statistics file \"%s\"",
+                                                                       statfile)));
                                        goto done;
                                }
 
@@ -3491,7 +3507,8 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
                                if (found)
                                {
                                        ereport(pgStatRunningInCollector ? LOG : WARNING,
-                                                       (errmsg("corrupted pgstat.stat file")));
+                                                       (errmsg("corrupted statistics file \"%s\"",
+                                                                       statfile)));
                                        goto done;
                                }
 
@@ -3506,7 +3523,8 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
                                                  fpin) != sizeof(PgStat_StatFuncEntry))
                                {
                                        ereport(pgStatRunningInCollector ? LOG : WARNING,
-                                                       (errmsg("corrupted pgstat.stat file")));
+                                                       (errmsg("corrupted statistics file \"%s\"",
+                                                                       statfile)));
                                        goto done;
                                }
 
@@ -3523,7 +3541,8 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
                                if (found)
                                {
                                        ereport(pgStatRunningInCollector ? LOG : WARNING,
-                                                       (errmsg("corrupted pgstat.stat file")));
+                                                       (errmsg("corrupted statistics file \"%s\"",
+                                                                       statfile)));
                                        goto done;
                                }
 
@@ -3538,7 +3557,8 @@ pgstat_read_statsfile(Oid onlydb, bool permanent)
 
                        default:
                                ereport(pgStatRunningInCollector ? LOG : WARNING,
-                                               (errmsg("corrupted pgstat.stat file")));
+                                               (errmsg("corrupted statistics file \"%s\"",
+                                                               statfile)));
                                goto done;
                }
        }
@@ -3568,10 +3588,18 @@ pgstat_read_statsfile_timestamp(bool permanent, TimestampTz *ts)
        const char *statfile = permanent ? PGSTAT_STAT_PERMANENT_FILENAME : pgstat_stat_filename;
 
        /*
-        * Try to open the status file.
+        * Try to open the status file.  As above, anything but ENOENT is worthy
+        * of complaining about.
         */
        if ((fpin = AllocateFile(statfile, PG_BINARY_R)) == NULL)
+       {
+               if (errno != ENOENT)
+                       ereport(pgStatRunningInCollector ? LOG : WARNING,
+                                       (errcode_for_file_access(),
+                                        errmsg("could not open statistics file \"%s\": %m",
+                                                       statfile)));
                return false;
+       }
 
        /*
         * Verify it's of the expected format.
@@ -3579,6 +3607,8 @@ pgstat_read_statsfile_timestamp(bool permanent, TimestampTz *ts)
        if (fread(&format_id, 1, sizeof(format_id), fpin) != sizeof(format_id)
                || format_id != PGSTAT_FILE_FORMAT_ID)
        {
+               ereport(pgStatRunningInCollector ? LOG : WARNING,
+                               (errmsg("corrupted statistics file \"%s\"", statfile)));
                FreeFile(fpin);
                return false;
        }
@@ -3588,6 +3618,8 @@ pgstat_read_statsfile_timestamp(bool permanent, TimestampTz *ts)
         */
        if (fread(&myGlobalStats, 1, sizeof(myGlobalStats), fpin) != sizeof(myGlobalStats))
        {
+               ereport(pgStatRunningInCollector ? LOG : WARNING,
+                               (errmsg("corrupted statistics file \"%s\"", statfile)));
                FreeFile(fpin);
                return false;
        }