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Get rid of not-very-portable fcntl(F_SETLK) mechanism for locking the Unix

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socket file, in favor of having an ordinary lockfile beside the socket file.
Clean up a few robustness problems in the lockfile code.  If postmaster is
going to reject a connection request based on database state, it will now
tell you so before authentication exchange not after.  (Of course, a failure
after is still possible if conditions change meanwhile, but this makes life
easier for a yet-to-be-written pg_ping utility.)
This commit is contained in:
Tom Lane
2000-11-29 20:59:54 +00:00
parent 1efd7330cb
commit 792b0f4666
10 changed files with 498 additions and 566 deletions
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75
src/backend/libpq/pqcomm.c
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@@ -29,7 +29,7 @@
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: pqcomm.c,v 1.113 2000/11/21 23:03:53 petere Exp $
* $Id: pqcomm.c,v 1.114 2000/11/29 20:59:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -169,7 +169,7 @@ StreamDoUnlink(void)
/*
* StreamServerPort -- open a sock stream "listening" port.
*
* This initializes the Postmaster's connection-accepting port fdP.
* This initializes the Postmaster's connection-accepting port *fdP.
*
* RETURNS: STATUS_OK or STATUS_ERROR
*/
@@ -183,9 +183,6 @@ StreamServerPort(int family, char *hostName, unsigned short portNumber,
err;
size_t len = 0;
int one = 1;
#ifdef HAVE_FCNTL_SETLK
int lock_fd;
#endif
Assert(family == AF_INET || family == AF_UNIX);
@@ -223,22 +220,15 @@ StreamServerPort(int family, char *hostName, unsigned short portNumber,
len = UNIXSOCK_LEN(saddr.un);
strcpy(sock_path, saddr.un.sun_path);
/*
* If the socket exists but nobody has an advisory lock on it we
* can safely delete the file.
* Grab an interlock file associated with the socket file.
*/
#ifdef HAVE_FCNTL_SETLK
if ((lock_fd = open(sock_path, O_WRONLY | O_NONBLOCK | PG_BINARY, 0666)) >= 0)
{
struct flock lck;
lck.l_whence = SEEK_SET;
lck.l_start = lck.l_len = 0;
lck.l_type = F_WRLCK;
if (fcntl(lock_fd, F_SETLK, &lck) != -1)
unlink(sock_path);
close(lock_fd);
}
#endif /* HAVE_FCNTL_SETLK */
if (! CreateSocketLockFile(sock_path, true))
return STATUS_ERROR;
/*
* Once we have the interlock, we can safely delete any pre-existing
* socket file to avoid failure at bind() time.
*/
unlink(sock_path);
}
#endif /* HAVE_UNIX_SOCKETS */
@@ -274,8 +264,8 @@ StreamServerPort(int family, char *hostName, unsigned short portNumber,
{
snprintf(PQerrormsg, PQERRORMSG_LENGTH,
"FATAL: StreamServerPort: bind() failed: %s\n"
"\tIs another postmaster already running on that port?\n",
strerror(errno));
"\tIs another postmaster already running on port %d?\n",
strerror(errno), (int) portNumber);
if (family == AF_UNIX)
snprintf(PQerrormsg + strlen(PQerrormsg),
PQERRORMSG_LENGTH - strlen(PQerrormsg),
@@ -293,41 +283,14 @@ StreamServerPort(int family, char *hostName, unsigned short portNumber,
#ifdef HAVE_UNIX_SOCKETS
if (family == AF_UNIX)
{
/* Arrange to unlink the socket file at exit */
on_proc_exit(StreamDoUnlink, 0);
/*
* Open the socket file and get an advisory lock on it. The
* lock_fd is left open to keep the lock.
* Fix socket ownership/permission if requested. Note we must
* do this before we listen() to avoid a window where unwanted
* connections could get accepted.
*/
#ifdef HAVE_FCNTL_SETLK
if ((lock_fd = open(sock_path, O_WRONLY | O_NONBLOCK | PG_BINARY, 0666)) >= 0)
{
struct flock lck;
lck.l_whence = SEEK_SET;
lck.l_start = lck.l_len = 0;
lck.l_type = F_WRLCK;
if (fcntl(lock_fd, F_SETLK, &lck) != 0)
elog(DEBUG, "flock error on %s: %s", sock_path, strerror(errno));
}
#endif /* HAVE_FCNTL_SETLK */
}
#endif /* HAVE_UNIX_SOCKETS */
listen(fd, SOMAXCONN);
/*
* MS: I took this code from Dillon's version. It makes the listening
* port non-blocking. That is not necessary (and may tickle kernel
* bugs).
*
* fcntl(fd, F_SETFD, 1); fcntl(fd, F_SETFL, FNDELAY);
*/
*fdP = fd;
if (family == AF_UNIX)
{
Assert(Unix_socket_group);
if (Unix_socket_group[0] != '\0')
{
@@ -379,6 +342,12 @@ StreamServerPort(int family, char *hostName, unsigned short portNumber,
return STATUS_ERROR;
}
}
#endif /* HAVE_UNIX_SOCKETS */
listen(fd, SOMAXCONN);
*fdP = fd;
return STATUS_OK;
}