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Before deciding we can use a socket for statistics collection, test to

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ensure that it actually passes data.  This catches cases such as a kernel
packet filter rule that makes the socket useless.

Andrew Dunstan
This commit is contained in:
Tom Lane 2004-03-22 23:55:29 +00:00
parent 6b198d61f8
commit 0d88dd1e50
1 changed files with 86 additions and 1 deletions
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87
src/backend/postmaster/pgstat.c
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@ -13,7 +13,7 @@
*
* Copyright (c) 2001-2003, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.61 2004/03/15 16:21:37 momjian Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.62 2004/03/22 23:55:29 tgl Exp $
* ----------
*/
#include "postgres.h"
@ -191,6 +191,12 @@ pgstat_init(void)
*addr,
hints;
int ret;
fd_set rset;
struct timeval tv;
char test_byte;
int sel_res;
#define TESTBYTEVAL ((char) 199)
/*
* Force start of collector daemon if something to collect
@ -308,6 +314,85 @@ pgstat_init(void)
continue;
}
/*
* Try to send and receive a one-byte test message on the socket.
* This is to catch situations where the socket can be created but
* will not actually pass data (for instance, because kernel packet
* filtering rules prevent it).
*/
test_byte = TESTBYTEVAL;
if (send(pgStatSock, &test_byte, 1, 0) != 1)
{
ereport(LOG,
(errcode_for_socket_access(),
errmsg("could not send test message on socket for statistics collector: %m")));
closesocket(pgStatSock);
pgStatSock = -1;
continue;
}
/*
* There could possibly be a little delay before the message can be
* received. We arbitrarily allow up to half a second before deciding
* it's broken.
*/
for (;;) /* need a loop to handle EINTR */
{
FD_ZERO(&rset);
FD_SET(pgStatSock, &rset);
tv.tv_sec = 0;
tv.tv_usec = 500000;
sel_res = select(pgStatSock+1, &rset, NULL, NULL, &tv);
if (sel_res >= 0 || errno != EINTR)
break;
}
if (sel_res < 0)
{
ereport(LOG,
(errcode_for_socket_access(),
errmsg("select() failed in statistics collector: %m")));
closesocket(pgStatSock);
pgStatSock = -1;
continue;
}
if (sel_res == 0 || !FD_ISSET(pgStatSock, &rset))
{
/*
* This is the case we actually think is likely, so take pains to
* give a specific message for it.
*
* errno will not be set meaningfully here, so don't use it.
*/
ereport(LOG,
(ERRCODE_CONNECTION_FAILURE,
errmsg("test message did not get through on socket for statistics collector")));
closesocket(pgStatSock);
pgStatSock = -1;
continue;
}
test_byte++; /* just make sure variable is changed */
if (recv(pgStatSock, &test_byte, 1, 0) != 1)
{
ereport(LOG,
(errcode_for_socket_access(),
errmsg("could not receive test message on socket for statistics collector: %m")));
closesocket(pgStatSock);
pgStatSock = -1;
continue;
}
if (test_byte != TESTBYTEVAL) /* strictly paranoia ... */
{
ereport(LOG,
(ERRCODE_INTERNAL_ERROR,
errmsg("incorrect test message transmission on socket for statistics collector")));
closesocket(pgStatSock);
pgStatSock = -1;
continue;
}
/* If we get here, we have a working socket */
break;
}