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Commit51e8e18

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Massimo Dal Zotto <dz@cs.unitn.it>> socket-flock.patch>> use advisory locks to check if the unix socket can be deleted.> A running postmaster keeps a lock on that file. A starting> postmaster exits if the file exists and is locked, otherwise> it deletes the sockets and proceeds.> This avoid the need to remove manually the file after a postmaster> or system crash.> I don't know if flock is available on any system. If not we could> define a HAVE_FLOCK set by configure.
1 parent53d7d47 commit51e8e18

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-4
lines changed

1 file changed

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‎src/backend/libpq/pqcomm.c

Lines changed: 35 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/libpq/pqcomm.c,v 1.50 1998/07/26 04:30:28 scrappy Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/libpq/pqcomm.c,v 1.51 1998/08/25 21:32:10 scrappy Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -55,6 +55,7 @@
5555
#include<netinet/in.h>
5656
#include<netinet/tcp.h>
5757
#include<arpa/inet.h>
58+
#include<sys/file.h>
5859

5960
#if defined(linux)
6061
#ifndefSOMAXCONN
@@ -70,6 +71,7 @@
7071
#ifdefMULTIBYTE
7172
#include"mb/pg_wchar.h"
7273
#endif
74+
#include"utils/trace.h"
7375

7476
/* ----------------
7577
*declarations
@@ -522,6 +524,7 @@ StreamServerPort(char *hostName, short portName, int *fdP)
522524
family;
523525
size_tlen;
524526
intone=1;
527+
intlock_fd;
525528

526529
family= ((hostName!=NULL) ?AF_INET :AF_UNIX);
527530

@@ -550,6 +553,20 @@ StreamServerPort(char *hostName, short portName, int *fdP)
550553
{
551554
len=UNIXSOCK_PATH(saddr.un,portName);
552555
strcpy(sock_path,saddr.un.sun_path);
556+
557+
/*
558+
* If the socket exists but nobody has an advisory lock on it
559+
* we can safely delete the file.
560+
*/
561+
if ((lock_fd=open(sock_path,O_RDONLY|O_NONBLOCK,0666)) >=0) {
562+
if (flock(lock_fd,LOCK_EX|LOCK_NB)==0) {
563+
TPRINTF(TRACE_VERBOSE,"flock on %s, deleting",sock_path);
564+
unlink(sock_path);
565+
}else {
566+
TPRINTF(TRACE_VERBOSE,"flock failed for %s",sock_path);
567+
}
568+
close(lock_fd);
569+
}
553570
}
554571
else
555572
{
@@ -564,18 +581,32 @@ StreamServerPort(char *hostName, short portName, int *fdP)
564581
"FATAL: StreamServerPort: bind() failed: errno=%d\n",
565582
errno);
566583
pqdebug("%s",PQerrormsg);
567-
strcat(PQerrormsg,"\tIs another postmaster already running on that port?\n");
584+
strcat(PQerrormsg,
585+
"\tIs another postmaster already running on that port?\n");
568586
if (family==AF_UNIX)
569-
strcat(PQerrormsg,"\tIf not, remove socket node (/tmp/.s.PGSQL.<portnumber>)and retry.\n");
587+
sprintf(PQerrormsg+strlen(PQerrormsg),
588+
"\tIf not, remove socket node (%s) and retry.\n",
589+
sock_path);
570590
else
571591
strcat(PQerrormsg,"\tIf not, wait a few seconds and retry.\n");
572592
fputs(PQerrormsg,stderr);
573593
return (STATUS_ERROR);
574594
}
575595

576-
if (family==AF_UNIX)
596+
if (family==AF_UNIX) {
577597
on_proc_exit(StreamDoUnlink,NULL);
578598

599+
/*
600+
* Open the socket file and get an advisory lock on it.
601+
* The lock_fd is left open to keep the lock.
602+
*/
603+
if ((lock_fd=open(sock_path,O_RDONLY|O_NONBLOCK,0666)) >=0) {
604+
if (flock(lock_fd,LOCK_EX|LOCK_NB)!=0) {
605+
TPRINTF(TRACE_VERBOSE,"flock error for %s",sock_path);
606+
}
607+
}
608+
}
609+
579610
listen(fd,SOMAXCONN);
580611

581612
/*

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