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Re-revert stats collector latch changes. 

This reverts commit cb2f2873d6, restoring
the latch-ified stats collector logic.  We'll soon see if this works any
better on the Windows buildfarm machines.
This commit is contained in:
Tom Lane 2012-05-13 14:44:39 -04:00
parent b85427f227
commit 966970ed63
1 changed files with 68 additions and 117 deletions
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185
src/backend/postmaster/pgstat.c
View File

@ -28,12 +28,6 @@
#include <arpa/inet.h>
#include <signal.h>
#include <time.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#ifdef HAVE_SYS_POLL_H
#include <sys/poll.h>
#endif
#include "pgstat.h"
@ -55,8 +49,8 @@
#include "storage/backendid.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/latch.h"
#include "storage/pg_shmem.h"
#include "storage/pmsignal.h"
#include "storage/procsignal.h"
#include "utils/ascii.h"
#include "utils/guc.h"
@ -94,9 +88,6 @@
* failed statistics collector; in
* seconds. */
#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)
#define PGSTAT_INQ_LOOP_COUNT (PGSTAT_INQ_INTERVAL / PGSTAT_RETRY_DELAY)
@ -139,6 +130,8 @@ PgStat_MsgBgWriter BgWriterStats;
*/
NON_EXEC_STATIC pgsocket pgStatSock = PGINVALID_SOCKET;
static Latch pgStatLatch;
static struct sockaddr_storage pgStatAddr;
static time_t last_pgstat_start_time;
@ -3009,15 +3002,7 @@ PgstatCollectorMain(int argc, char *argv[])
{
int len;
PgStat_Msg msg;
#ifndef WIN32
#ifdef HAVE_POLL
struct pollfd input_fd;
#else
struct timeval sel_timeout;
fd_set rfds;
#endif
#endif
int wr;
IsUnderPostmaster = true; /* we are a postmaster subprocess now */
@ -3036,9 +3021,13 @@ PgstatCollectorMain(int argc, char *argv[])
elog(FATAL, "setsid() failed: %m");
#endif
/* Initialize private latch for use by signal handlers */
InitLatch(&pgStatLatch);
/*
* Ignore all signals usually bound to some action in the postmaster,
* except SIGQUIT.
* except SIGHUP and SIGQUIT. Note we don't need a SIGUSR1 handler to
* support latch operations, because pgStatLatch is local not shared.
*/
pqsignal(SIGHUP, pgstat_sighup_handler);
pqsignal(SIGINT, SIG_IGN);
@ -3073,26 +3062,24 @@ PgstatCollectorMain(int argc, char *argv[])
pgStatRunningInCollector = true;
pgStatDBHash = pgstat_read_statsfile(InvalidOid, true);
/*
* Setup the descriptor set for select(2). Since only one bit in the set
* ever changes, we need not repeat FD_ZERO each time.
*/
#if !defined(HAVE_POLL) && !defined(WIN32)
FD_ZERO(&rfds);
#endif
/*
* Loop to process messages until we get SIGQUIT or detect ungraceful
* death of our parent postmaster.
*
* For performance reasons, we don't want to do a PostmasterIsAlive() test
* 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 performance reasons, we don't want to do ResetLatch/WaitLatch after
* every message; instead, do that only after a recv() fails to obtain a
* message. (This effectively means that if backends are sending us stuff
* like mad, we won't notice postmaster death until things slack off a
* bit; which seems fine.) To do that, we have an inner loop that
* iterates as long as recv() succeeds. We do recognize got_SIGHUP inside
* the inner loop, which means that such interrupts will get serviced but
* the latch won't get cleared until next time there is a break in the
* action.
*/
for (;;)
{
int got_data;
/* Clear any already-pending wakeups */
ResetLatch(&pgStatLatch);
/*
* Quit if we get SIGQUIT from the postmaster.
@ -3101,87 +3088,37 @@ PgstatCollectorMain(int argc, char *argv[])
break;
/*
* Reload configuration if we got SIGHUP from the postmaster.
* Inner loop iterates as long as we keep getting messages, or until
* need_exit becomes set.
*/
if (got_SIGHUP)
while (!need_exit)
{
ProcessConfigFile(PGC_SIGHUP);
got_SIGHUP = false;
}
/*
* Reload configuration if we got SIGHUP from the postmaster.
*/
if (got_SIGHUP)
{
got_SIGHUP = false;
ProcessConfigFile(PGC_SIGHUP);
}
/*
* Write the stats file if a new request has arrived that is not
* satisfied by existing file.
*/
if (last_statwrite < last_statrequest)
pgstat_write_statsfile(false);
/*
* Write the stats file if a new request has arrived that is not
* satisfied by existing file.
*/
if (last_statwrite < last_statrequest)
pgstat_write_statsfile(false);
/*
* Wait for a message to arrive; but not for more than
* PGSTAT_SELECT_TIMEOUT seconds. (This determines how quickly we will
* shut down after an ungraceful postmaster termination; so it needn't
* be very fast. However, on some systems SIGQUIT won't interrupt the
* poll/select call, so this also limits speed of response to SIGQUIT,
* which is more important.)
*
* We use poll(2) if available, otherwise select(2). Win32 has its own
* implementation.
*/
#ifndef WIN32
#ifdef HAVE_POLL
input_fd.fd = pgStatSock;
input_fd.events = POLLIN | POLLERR;
input_fd.revents = 0;
if (poll(&input_fd, 1, PGSTAT_SELECT_TIMEOUT * 1000) < 0)
{
if (errno == EINTR)
continue;
ereport(ERROR,
(errcode_for_socket_access(),
errmsg("poll() failed in statistics collector: %m")));
}
got_data = (input_fd.revents != 0);
#else /* !HAVE_POLL */
FD_SET(pgStatSock, &rfds);
/*
* timeout struct is modified by select() on some operating systems,
* so re-fill it each time.
*/
sel_timeout.tv_sec = PGSTAT_SELECT_TIMEOUT;
sel_timeout.tv_usec = 0;
if (select(pgStatSock + 1, &rfds, NULL, NULL, &sel_timeout) < 0)
{
if (errno == EINTR)
continue;
ereport(ERROR,
(errcode_for_socket_access(),
errmsg("select() failed in statistics collector: %m")));
}
got_data = FD_ISSET(pgStatSock, &rfds);
#endif /* HAVE_POLL */
#else /* WIN32 */
got_data = pgwin32_waitforsinglesocket(pgStatSock, FD_READ,
PGSTAT_SELECT_TIMEOUT * 1000);
#endif
/*
* If there is a message on the socket, read it and check for
* validity.
*/
if (got_data)
{
/*
* Try to receive and process a message. This will not block,
* since the socket is set to non-blocking mode.
*/
len = recv(pgStatSock, (char *) &msg,
sizeof(PgStat_Msg), 0);
if (len < 0)
{
if (errno == EINTR)
continue;
if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)
break; /* out of inner loop */
ereport(ERROR,
(errcode_for_socket_access(),
errmsg("could not read statistics message: %m")));
@ -3279,17 +3216,21 @@ PgstatCollectorMain(int argc, char *argv[])
default:
break;
}
}
else
{
/*
* We can only get here if the select/poll timeout elapsed. Check
* for postmaster death.
*/
if (!PostmasterIsAlive())
break;
}
} /* end of message-processing loop */
} /* end of inner message-processing loop */
/* Sleep until there's something to do */
wr = WaitLatchOrSocket(&pgStatLatch,
WL_LATCH_SET | WL_POSTMASTER_DEATH | WL_SOCKET_READABLE,
pgStatSock,
-1L);
/*
* Emergency bailout if postmaster has died. This is to avoid the
* necessity for manual cleanup of all postmaster children.
*/
if (wr & WL_POSTMASTER_DEATH)
break;
} /* end of outer loop */
/*
* Save the final stats to reuse at next startup.
@ -3304,14 +3245,24 @@ PgstatCollectorMain(int argc, char *argv[])
static void
pgstat_exit(SIGNAL_ARGS)
{
int save_errno = errno;
need_exit = true;
SetLatch(&pgStatLatch);
errno = save_errno;
}
/* SIGHUP handler for collector process */
static void
pgstat_sighup_handler(SIGNAL_ARGS)
{
int save_errno = errno;
got_SIGHUP = true;
SetLatch(&pgStatLatch);
errno = save_errno;
}