*
* Copyright (c) 2001-2008, PostgreSQL Global Development Group
*
- * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.181 2008/08/25 18:55:43 mha Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.182 2008/11/03 01:17:08 tgl Exp $
* ----------
*/
#include "postgres.h"
* Timer definitions.
* ----------
*/
-#define PGSTAT_STAT_INTERVAL 500 /* How often to write the status file;
- * in milliseconds. */
+#define PGSTAT_STAT_INTERVAL 500 /* Minimum time between stats file
+ * updates; in milliseconds. */
+
+#define PGSTAT_RETRY_DELAY 10 /* How long to wait between statistics
+ * update requests; in milliseconds. */
+
+#define PGSTAT_MAX_WAIT_TIME 5000 /* Maximum time to wait for a stats
+ * file update; in milliseconds. */
#define PGSTAT_RESTART_INTERVAL 60 /* How often to attempt to restart a
* failed statistics collector; in
#define PGSTAT_SELECT_TIMEOUT 2 /* How often to check for postmaster
* death; in seconds. */
+#define PGSTAT_POLL_LOOP_COUNT (PGSTAT_MAX_WAIT_TIME / PGSTAT_RETRY_DELAY)
+
/* ----------
* The initial size hints for the hash tables used in the collector.
*/
static HTAB *pgStatFunctions = NULL;
+/*
+ * Indicates if backend has some function stats that it hasn't yet
+ * sent to the collector.
+ */
+static bool have_function_stats = false;
+
/*
* Tuple insertion/deletion counts for an open transaction can't be propagated
* into PgStat_TableStatus counters until we know if it is going to commit
*/
static PgStat_GlobalStats globalStats;
+/* Last time the collector successfully wrote the stats file */
+static TimestampTz last_statwrite;
+/* Latest statistics request time from backends */
+static TimestampTz last_statrequest;
+
static volatile bool need_exit = false;
-static volatile bool need_statwrite = false;
static volatile bool got_SIGHUP = false;
/*
NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]);
static void pgstat_exit(SIGNAL_ARGS);
-static void force_statwrite(SIGNAL_ARGS);
static void pgstat_beshutdown_hook(int code, Datum arg);
static void pgstat_sighup_handler(SIGNAL_ARGS);
static void pgstat_setheader(PgStat_MsgHdr *hdr, StatMsgType mtype);
static void pgstat_send(void *msg, int len);
+static void pgstat_recv_inquiry(PgStat_MsgInquiry *msg, int len);
static void pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len);
static void pgstat_recv_tabpurge(PgStat_MsgTabpurge *msg, int len);
static void pgstat_recv_dropdb(PgStat_MsgDropdb *msg, int len);
int i;
/* Don't expend a clock check if nothing to do */
- /* Note: we ignore pending function stats in this test ... OK? */
- if (pgStatTabList == NULL ||
- pgStatTabList->tsa_used == 0)
+ if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0)
+ && !have_function_stats)
return;
/*
if (msg.m_nentries > 0)
pgstat_send(&msg, offsetof(PgStat_MsgFuncstat, m_entry[0]) +
msg.m_nentries * sizeof(PgStat_FunctionEntry));
+
+ have_function_stats = false;
}
pgstat_send(&msg, sizeof(msg));
}
+/* ----------
+ * pgstat_send_inquiry() -
+ *
+ * Notify collector that we need fresh data.
+ * ts specifies the minimum acceptable timestamp for the stats file.
+ * ----------
+ */
+static void
+pgstat_send_inquiry(TimestampTz ts)
+{
+ PgStat_MsgInquiry msg;
+
+ pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_INQUIRY);
+ msg.inquiry_time = ts;
+ pgstat_send(&msg, sizeof(msg));
+}
+
+
/*
* Initialize function call usage data.
* Called by the executor before invoking a function.
fs->f_numcalls++;
fs->f_time = f_total;
INSTR_TIME_ADD(fs->f_time_self, f_self);
+
+ /* indicate that we have something to send */
+ have_function_stats = true;
}
NON_EXEC_STATIC void
PgstatCollectorMain(int argc, char *argv[])
{
- struct itimerval write_timeout;
- bool need_timer = false;
int len;
PgStat_Msg msg;
/*
* Ignore all signals usually bound to some action in the postmaster,
- * except SIGQUIT and SIGALRM.
+ * except SIGQUIT.
*/
pqsignal(SIGHUP, pgstat_sighup_handler);
pqsignal(SIGINT, SIG_IGN);
pqsignal(SIGTERM, SIG_IGN);
pqsignal(SIGQUIT, pgstat_exit);
- pqsignal(SIGALRM, force_statwrite);
+ pqsignal(SIGALRM, SIG_IGN);
pqsignal(SIGPIPE, SIG_IGN);
pqsignal(SIGUSR1, SIG_IGN);
pqsignal(SIGUSR2, SIG_IGN);
/*
* Arrange to write the initial status file right away
*/
- need_statwrite = true;
-
- /* Preset the delay between status file writes */
- MemSet(&write_timeout, 0, sizeof(struct itimerval));
- write_timeout.it_value.tv_sec = PGSTAT_STAT_INTERVAL / 1000;
- write_timeout.it_value.tv_usec = (PGSTAT_STAT_INTERVAL % 1000) * 1000;
+ last_statrequest = GetCurrentTimestamp();
+ last_statwrite = last_statrequest - 1;
/*
* Read in an existing statistics stats file or initialize the stats to
* death of our parent postmaster.
*
* For performance reasons, we don't want to do a PostmasterIsAlive() test
- * after every message; instead, do it at statwrite time and if
- * select()/poll() is interrupted by timeout.
+ * after every message; instead, do it only when select()/poll() is
+ * interrupted by timeout. In essence, we'll stay alive as long as
+ * backends keep sending us stuff often, even if the postmaster is gone.
*/
for (;;)
{
/*
* Reload configuration if we got SIGHUP from the postmaster.
- * Also, signal a new write of the file, so we drop a new file as
- * soon as possible of the directory for it changes.
*/
if (got_SIGHUP)
{
ProcessConfigFile(PGC_SIGHUP);
got_SIGHUP = false;
- need_statwrite = true;
}
/*
- * If time to write the stats file, do so. Note that the alarm
- * interrupt isn't re-enabled immediately, but only after we next
- * receive a stats message; so no cycles are wasted when there is
- * nothing going on.
+ * Write the stats file if a new request has arrived that is not
+ * satisfied by existing file.
*/
- if (need_statwrite)
- {
- /* Check for postmaster death; if so we'll write file below */
- if (!PostmasterIsAlive(true))
- break;
-
+ if (last_statwrite < last_statrequest)
pgstat_write_statsfile(false);
- need_statwrite = false;
- need_timer = true;
- }
/*
* Wait for a message to arrive; but not for more than
case PGSTAT_MTYPE_DUMMY:
break;
+ case PGSTAT_MTYPE_INQUIRY:
+ pgstat_recv_inquiry((PgStat_MsgInquiry *) &msg, len);
+ break;
+
case PGSTAT_MTYPE_TABSTAT:
pgstat_recv_tabstat((PgStat_MsgTabstat *) &msg, len);
break;
default:
break;
}
-
- /*
- * If this is the first message after we wrote the stats file the
- * last time, enable the alarm interrupt to make it be written
- * again later.
- */
- if (need_timer)
- {
- if (setitimer(ITIMER_REAL, &write_timeout, NULL))
- ereport(ERROR,
- (errmsg("could not set statistics collector timer: %m")));
- need_timer = false;
- }
}
else
{
need_exit = true;
}
-/* SIGALRM signal handler for collector process */
-static void
-force_statwrite(SIGNAL_ARGS)
-{
- need_statwrite = true;
-}
-
/* SIGHUP handler for collector process */
static void
pgstat_sighup_handler(SIGNAL_ARGS)
/*
* Open the statistics temp file to write out the current values.
*/
- fpout = fopen(tmpfile, PG_BINARY_W);
+ fpout = AllocateFile(tmpfile, PG_BINARY_W);
if (fpout == NULL)
{
ereport(LOG,
return;
}
+ /*
+ * Set the timestamp of the stats file.
+ */
+ globalStats.stats_timestamp = GetCurrentTimestamp();
+
/*
* Write the file header --- currently just a format ID.
*/
(errcode_for_file_access(),
errmsg("could not write temporary statistics file \"%s\": %m",
tmpfile)));
- fclose(fpout);
+ FreeFile(fpout);
unlink(tmpfile);
}
- else if (fclose(fpout) < 0)
+ else if (FreeFile(fpout) < 0)
{
ereport(LOG,
(errcode_for_file_access(),
tmpfile, statfile)));
unlink(tmpfile);
}
+ else
+ {
+ /*
+ * Successful write, so update last_statwrite.
+ */
+ last_statwrite = globalStats.stats_timestamp;
+
+ /*
+ * 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.
+ * This ensures that no inquiry message can cause more than one stats
+ * file write to occur.
+ */
+ last_statrequest = last_statwrite;
+ }
if (permanent)
unlink(pgstat_stat_filename);
return dbhash;
}
+/* ----------
+ * pgstat_read_statsfile_timestamp() -
+ *
+ * Attempt to fetch the timestamp of an existing stats file.
+ * Returns TRUE if successful (timestamp is stored at *ts).
+ * ----------
+ */
+static bool
+pgstat_read_statsfile_timestamp(bool permanent, TimestampTz *ts)
+{
+ PgStat_GlobalStats myGlobalStats;
+ FILE *fpin;
+ int32 format_id;
+ const char *statfile = permanent?PGSTAT_STAT_PERMANENT_FILENAME:pgstat_stat_filename;
+
+ /*
+ * Try to open the status file.
+ */
+ if ((fpin = AllocateFile(statfile, PG_BINARY_R)) == NULL)
+ return false;
+
+ /*
+ * Verify it's of the expected format.
+ */
+ if (fread(&format_id, 1, sizeof(format_id), fpin) != sizeof(format_id)
+ || format_id != PGSTAT_FILE_FORMAT_ID)
+ {
+ FreeFile(fpin);
+ return false;
+ }
+
+ /*
+ * Read global stats struct
+ */
+ if (fread(&myGlobalStats, 1, sizeof(myGlobalStats), fpin) != sizeof(myGlobalStats))
+ {
+ FreeFile(fpin);
+ return false;
+ }
+
+ *ts = myGlobalStats.stats_timestamp;
+
+ FreeFile(fpin);
+ return true;
+}
+
/*
* If not already done, read the statistics collector stats file into
* some hash tables. The results will be kept until pgstat_clear_snapshot()
static void
backend_read_statsfile(void)
{
+ TimestampTz min_ts;
+ int count;
+
/* already read it? */
if (pgStatDBHash)
return;
Assert(!pgStatRunningInCollector);
+ /*
+ * We set the minimum acceptable timestamp to PGSTAT_STAT_INTERVAL msec
+ * before now. This indirectly ensures that the collector needn't write
+ * the file more often than PGSTAT_STAT_INTERVAL.
+ *
+ * Note that we don't recompute min_ts after sleeping; so we might end up
+ * accepting a file a bit older than PGSTAT_STAT_INTERVAL. In practice
+ * that shouldn't happen, though, as long as the sleep time is less than
+ * PGSTAT_STAT_INTERVAL; and we don't want to lie to the collector about
+ * what our cutoff time really is.
+ */
+ min_ts = TimestampTzPlusMilliseconds(GetCurrentTimestamp(),
+ -PGSTAT_STAT_INTERVAL);
+
+ /*
+ * Loop until fresh enough stats file is available or we ran out of time.
+ * The stats inquiry message is sent repeatedly in case collector drops it.
+ */
+ for (count = 0; count < PGSTAT_POLL_LOOP_COUNT; count++)
+ {
+ TimestampTz file_ts;
+
+ CHECK_FOR_INTERRUPTS();
+
+ if (pgstat_read_statsfile_timestamp(false, &file_ts) &&
+ file_ts >= min_ts)
+ break;
+
+ /* Not there or too old, so kick the collector and wait a bit */
+ pgstat_send_inquiry(min_ts);
+ pg_usleep(PGSTAT_RETRY_DELAY * 1000L);
+ }
+
+ if (count >= PGSTAT_POLL_LOOP_COUNT)
+ elog(WARNING, "pgstat wait timeout");
+
/* Autovacuum launcher wants stats about all databases */
if (IsAutoVacuumLauncherProcess())
pgStatDBHash = pgstat_read_statsfile(InvalidOid, false);
}
+/* ----------
+ * pgstat_recv_inquiry() -
+ *
+ * Process stat inquiry requests.
+ * ----------
+ */
+static void
+pgstat_recv_inquiry(PgStat_MsgInquiry *msg, int len)
+{
+ if (msg->inquiry_time > last_statrequest)
+ last_statrequest = msg->inquiry_time;
+}
+
+
/* ----------
* pgstat_recv_tabstat() -
*
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