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Ensure that we retry rather than erroring out when send() or recv() return

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EINTR; the stats code was failing to do this and so were a couple of places
in the postmaster.  The stats code assumed that recv() could not return EINTR
if a preceding select() showed the socket to be read-ready, but this is
demonstrably false with our Windows implementation of recv(), and it may
not be the case on all Unix variants either.  I think this explains the
intermittent stats regression test failures we've been seeing, as well
as reports of stats collector instability under high load on Windows.

Backpatch as far as 8.0.
This commit is contained in:
Tom Lane 2006-07-16 18:17:23 +00:00
parent 78e8400a52
commit 74dac69e3c
2 changed files with 33 additions and 7 deletions
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27
src/backend/postmaster/pgstat.c
View File

@ -13,7 +13,7 @@
*
* Copyright (c) 2001-2005, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.111.2.5 2006/06/27 14:01:42 tgl Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.111.2.6 2006/07/16 18:17:23 tgl Exp $
* ----------
*/
#include "postgres.h"
@ -339,8 +339,12 @@ pgstat_init(void)
* rules prevent it).
*/
test_byte = TESTBYTEVAL;
retry1:
if (send(pgStatSock, &test_byte, 1, 0) != 1)
{
if (errno == EINTR)
goto retry1; /* if interrupted, just retry */
ereport(LOG,
(errcode_for_socket_access(),
errmsg("could not send test message on socket for statistics collector: %m")));
@ -391,8 +395,11 @@ pgstat_init(void)
test_byte++; /* just make sure variable is changed */
retry2:
if (recv(pgStatSock, &test_byte, 1, 0) != 1)
{
if (errno == EINTR)
goto retry2; /* if interrupted, just retry */
ereport(LOG,
(errcode_for_socket_access(),
errmsg("could not receive test message on socket for statistics collector: %m")));
@ -1431,17 +1438,23 @@ pgstat_setheader(PgStat_MsgHdr *hdr, StatMsgType mtype)
static void
pgstat_send(void *msg, int len)
{
int rc;
if (pgStatSock < 0)
return;
((PgStat_MsgHdr *) msg)->m_size = len;
/* We'll retry after EINTR, but ignore all other failures */
do
{
rc = send(pgStatSock, msg, len, 0);
} while (rc < 0 && errno == EINTR);
#ifdef USE_ASSERT_CHECKING
if (send(pgStatSock, msg, len, 0) < 0)
/* In debug builds, log send failures ... */
if (rc < 0)
elog(LOG, "could not send to statistics collector: %m");
#else
send(pgStatSock, msg, len, 0);
/* We deliberately ignore any error from send() */
#endif
}
@ -1972,9 +1985,13 @@ pgstat_recvbuffer(void)
len = recv(pgStatSock, (char *) &input_buffer,
sizeof(PgStat_Msg), 0);
if (len < 0)
{
if (errno == EINTR)
continue;
ereport(ERROR,
(errcode_for_socket_access(),
errmsg("could not read statistics message: %m")));
}
/*
* We ignore messages that are smaller than our common header

13
src/backend/postmaster/postmaster.c
View File

@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.475.2.5 2006/05/19 15:15:38 alvherre Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.475.2.6 2006/07/16 18:17:23 tgl Exp $
*
* NOTES
*
@ -1408,8 +1408,12 @@ ProcessStartupPacket(Port *port, bool SSLdone)
#else
SSLok = 'N'; /* No support for SSL */
#endif
retry1:
if (send(port->sock, &SSLok, 1, 0) != 1)
{
if (errno == EINTR)
goto retry1; /* if interrupted, just retry */
ereport(COMMERROR,
(errcode_for_socket_access(),
errmsg("failed to send SSL negotiation response: %m")));
@ -2545,6 +2549,7 @@ static void
report_fork_failure_to_client(Port *port, int errnum)
{
char buffer[1000];
int rc;
/* Format the error message packet (always V2 protocol) */
snprintf(buffer, sizeof(buffer), "E%s%s\n",
@ -2555,7 +2560,11 @@ report_fork_failure_to_client(Port *port, int errnum)
if (!pg_set_noblock(port->sock))
return;
send(port->sock, buffer, strlen(buffer) + 1, 0);
/* We'll retry after EINTR, but ignore all other failures */
do
{
rc = send(port->sock, buffer, strlen(buffer) + 1, 0);
} while (rc < 0 && errno == EINTR);
}