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 0d7f62965f484009c4df7a17a13cdf6895d61252..c00b87c8f3712f3b10684163554c1c6147388888 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;
    }