postmaster.c

关系型数据库 Postgresql 6.5.2

			int exitstatus)		/* child's exit status. */
{
	Dlelem	   *prev,
			   *curr;
	Backend    *bp;
	int			sig;

	if (DebugLvl)
	{
		fprintf(stderr, "%s: CleanupProc: pid %d exited with status %d\n",
				progname, pid, exitstatus);
	}

	/*
	 * If a backend dies in an ugly way (i.e. exit status not 0) then we
	 * must signal all other backends to quickdie.	If exit status is zero
	 * we assume everything is hunky dory and simply remove the backend
	 * from the active backend list.
	 */
	if (!exitstatus)
	{
		curr = DLGetHead(BackendList);
		while (curr)
		{
			bp = (Backend *) DLE_VAL(curr);
			if (bp->pid == pid)
			{
				DLRemove(curr);
				free(bp);
				DLFreeElem(curr);
				break;
			}
			curr = DLGetSucc(curr);
		}

		ProcRemove(pid);

		return;
	}

	curr = DLGetHead(BackendList);
	while (curr)
	{
		bp = (Backend *) DLE_VAL(curr);

		/* -----------------
		 * SIGUSR1 is the special signal that says exit
		 * without proc_exit and let the user know what's going on.
		 * ProcSemaphoreKill() cleans up the backends semaphore.  If
		 * SendStop is set (-s on command line), then we send a SIGSTOP so
		 * that we can core dumps from all backends by hand.
		 * -----------------
		 */
		sig = (SendStop) ? SIGSTOP : SIGUSR1;
		if (bp->pid != pid)
		{
			if (DebugLvl)
				fprintf(stderr, "%s: CleanupProc: sending %s to process %d\n",
						progname,
						(sig == SIGUSR1)
						? "SIGUSR1" : "SIGSTOP",
						bp->pid);
			kill(bp->pid, sig);
		}
		ProcRemove(bp->pid);

		prev = DLGetPred(curr);
		DLRemove(curr);
		free(bp);
		DLFreeElem(curr);
		if (!prev)
		{						/* removed head */
			curr = DLGetHead(BackendList);
			continue;
		}
		curr = DLGetSucc(prev);
	}

	/*
	 * Nothing up my sleeve here, ActiveBackends means that since the last
	 * time we recreated shared memory and sems another frontend has
	 * requested and received a connection and I have forked off another
	 * backend.  This prevents me from reinitializing shared stuff more
	 * than once for the set of backends that caused the failure and were
	 * killed off.
	 */
	if (ActiveBackends == TRUE && Reinit)
	{
		if (DebugLvl)
			fprintf(stderr, "%s: CleanupProc: reinitializing shared memory and semaphores\n",
					progname);
		shmem_exit(0);
		reset_shared(PostPortName);
	}
}

/*
 * Send a signal to all chidren processes.
 */
static void
SignalChildren(int signal)
{
	Dlelem	   *curr,
			   *next;
	Backend    *bp;
	int			mypid = getpid();

	curr = DLGetHead(BackendList);
	while (curr)
	{
		next = DLGetSucc(curr);
		bp = (Backend *) DLE_VAL(curr);

		if (bp->pid != mypid)
		{
			TPRINTF(TRACE_VERBOSE,
					"SignalChildren: sending signal %d to process %d",
					signal, bp->pid);
			kill(bp->pid, signal);
		}

		curr = next;
	}
}

/*
 * BackendStartup -- start backend process
 *
 * returns: STATUS_ERROR if the fork/exec failed, STATUS_OK
 *		otherwise.
 *
 */
static int
BackendStartup(Port *port)
{
	Backend    *bn;				/* for backend cleanup */
	int			pid,
				i;

#ifdef CYR_RECODE
#define NR_ENVIRONMENT_VBL 6
	char		ChTable[80];

#else
#define NR_ENVIRONMENT_VBL 5
#endif

	static char envEntry[NR_ENVIRONMENT_VBL][2 * ARGV_SIZE];

	for (i = 0; i < NR_ENVIRONMENT_VBL; ++i)
		MemSet(envEntry[i], 0, 2 * ARGV_SIZE);

	/*
	 * Set up the necessary environment variables for the backend This
	 * should really be some sort of message....
	 */
	sprintf(envEntry[0], "POSTPORT=%d", PostPortName);
	putenv(envEntry[0]);
	sprintf(envEntry[1], "POSTID=%d", NextBackendTag);
	putenv(envEntry[1]);
	sprintf(envEntry[2], "PG_USER=%s", port->user);
	putenv(envEntry[2]);
	if (!getenv("PGDATA"))
	{
		sprintf(envEntry[3], "PGDATA=%s", DataDir);
		putenv(envEntry[3]);
	}
	sprintf(envEntry[4], "IPC_KEY=%d", ipc_key);
	putenv(envEntry[4]);

#ifdef CYR_RECODE
	GetCharSetByHost(ChTable, port->raddr.in.sin_addr.s_addr, DataDir);
	if (*ChTable != '\0')
	{
		sprintf(envEntry[5], "PG_RECODETABLE=%s", ChTable);
		putenv(envEntry[5]);
	}
#endif

	/*
	 * Compute the cancel key that will be assigned to this backend. The
	 * backend will have its own copy in the forked-off process' value of
	 * MyCancelKey, so that it can transmit the key to the frontend.
	 */
	MyCancelKey = PostmasterRandom();

	if (DebugLvl > 2)
	{
		char	  **p;
		extern char **environ;

		fprintf(stderr, "%s: BackendStartup: environ dump:\n",
				progname);
		fprintf(stderr, "-----------------------------------------\n");
		for (p = environ; *p; ++p)
			fprintf(stderr, "\t%s\n", *p);
		fprintf(stderr, "-----------------------------------------\n");
	}

	/*
	 * Flush stdio channels just before fork, to avoid double-output
	 * problems. Ideally we'd use fflush(NULL) here, but there are still a
	 * few non-ANSI stdio libraries out there (like SunOS 4.1.x) that
	 * coredump if we do. Presently stdout and stderr are the only stdio
	 * output channels used by the postmaster, so fflush'ing them should
	 * be sufficient.
	 */
	fflush(stdout);
	fflush(stderr);

	if ((pid = fork()) == 0)
	{							/* child */
		if (DoBackend(port))
		{
			fprintf(stderr, "%s child[%d]: BackendStartup: backend startup failed\n",
					progname, (int) getpid());
			exit(1);
		}
		else
			exit(0);
	}

	/* in parent */
	if (pid < 0)
	{
		fprintf(stderr, "%s: BackendStartup: fork failed: %s\n",
				progname, strerror(errno));
		return STATUS_ERROR;
	}

	if (DebugLvl)
		fprintf(stderr, "%s: BackendStartup: pid %d user %s db %s socket %d\n",
				progname, pid, port->user, port->database,
				port->sock);

	/* Generate a new backend tag for every backend we start */

	/*
	 * XXX theoretically this could wrap around, if you have the patience
	 * to start 2^31 backends ...
	 */
	NextBackendTag -= 1;

	/*
	 * Everything's been successful, it's safe to add this backend to our
	 * list of backends.
	 */
	if (!(bn = (Backend *) calloc(1, sizeof(Backend))))
	{
		fprintf(stderr, "%s: BackendStartup: malloc failed\n",
				progname);
		ExitPostmaster(1);
	}

	bn->pid = pid;
	bn->cancel_key = MyCancelKey;
	DLAddHead(BackendList, DLNewElem(bn));

	ActiveBackends = TRUE;

	return STATUS_OK;
}

/*
 * split_opts -- split a string of options and append it to an argv array
 *
 * NB: the string is destructively modified!
 *
 * Since no current POSTGRES arguments require any quoting characters,
 * we can use the simple-minded tactic of assuming each set of space-
 * delimited characters is a separate argv element.
 *
 * If you don't like that, well, we *used* to pass the whole option string
 * as ONE argument to execl(), which was even less intelligent...
 */
static void
split_opts(char **argv, int *argcp, char *s)
{
	int			i = *argcp;

	while (s && *s)
	{
		while (isspace(*s))
			++s;
		if (*s == '\0')
			break;
		argv[i++] = s;
		while (*s && !isspace(*s))
			++s;
		if (*s)
			*s++ = '\0';
	}

	*argcp = i;
}

/*
 * DoBackend -- set up the backend's argument list and invoke backend main().
 *
 * This used to perform an execv() but we no longer exec the backend;
 * it's the same executable as the postmaster.
 *
 * returns:
 *		Shouldn't return at all.
 *		If PostgresMain() fails, return status.
 */
static int
DoBackend(Port *port)
{
	char	   *av[ARGV_SIZE * 2];
	int			ac = 0;
	char		execbuf[MAXPATHLEN];
	char		debugbuf[ARGV_SIZE];
	char		protobuf[ARGV_SIZE];
	char		dbbuf[ARGV_SIZE];
	char		optbuf[ARGV_SIZE];
	char		ttybuf[ARGV_SIZE];
	int			i;
	struct timeval now;
	struct timezone tz;

	/*
	 * Let's clean up ourselves as the postmaster child
	 */

	/* We don't want the postmaster's proc_exit() handlers */
	on_exit_reset();	

	/* ----------------
	 *	register signal handlers.
	 *	Thanks to the postmaster, these are currently blocked.
	 * ----------------
	 */
	pqsignal(SIGINT, die);

	pqsignal(SIGHUP, die);
	pqsignal(SIGTERM, die);
	pqsignal(SIGPIPE, die);
	pqsignal(SIGUSR1, quickdie);
	pqsignal(SIGUSR2, Async_NotifyHandler);
	pqsignal(SIGFPE, FloatExceptionHandler);

	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);

	/* OK, let's unblock our signals, all together now... */
	sigprocmask(SIG_SETMASK, &oldsigmask, 0);

	/* Close the postmaster sockets */
	if (NetServer)
		StreamClose(ServerSock_INET);
#ifndef __CYGWIN32__
	StreamClose(ServerSock_UNIX);
#endif

	/* Save port etc. for ps status */
	MyProcPort = port;

	MyProcPid = getpid();

	/*
	 * Don't want backend to be able to see the postmaster random number
	 * generator state.  We have to clobber the static random_seed *and*
	 * start a new random sequence in the random() library function.
	 */
	random_seed = 0;
	gettimeofday(&now, &tz);
	srandom(now.tv_usec);

	/* ----------------
	 * Now, build the argv vector that will be given to PostgresMain.
	 *
	 * The layout of the command line is
	 *		postgres [secure switches] -p databasename [insecure switches]
	 * where the switches after -p come from the client request.
	 * ----------------
	 */

	StrNCpy(execbuf, Execfile, MAXPATHLEN);
	av[ac++] = execbuf;

	/*
	 * We need to set our argv[0] to an absolute path name because some
	 * OS's use this for dynamic loading, like BSDI.  Without it, when we
	 * change directories to the database dir, the dynamic loader can't
	 * find the base executable and fails. Another advantage is that this
	 * changes the 'ps' displayed process name on some platforms.  It does
	 * on BSDI.  That's a big win.
	 */

#ifndef linux

	/*
	 * This doesn't work on linux and overwrites the only valid pointer to
	 * the argv buffer.  See PS_INIT_STATUS macro.
	 */
	real_argv[0] = Execfile;
#endif

	/*
	 * Pass the requested debugging level along to the backend.  We
	 * decrement by one; level one debugging in the postmaster traces
	 * postmaster connection activity, and levels two and higher are
	 * passed along to the backend.  This allows us to watch only the
	 * postmaster or the postmaster and the backend.
	 */
	if (DebugLvl > 1)
	{
		sprintf(debugbuf, "-d%d", DebugLvl);
		av[ac++] = debugbuf;
	}

	/*
	 * Pass any backend switches specified with -o in the postmaster's own
	 * command line.  We assume these are secure. (It's OK to mangle
	 * ExtraOptions since we are now in the child process; this won't
	 * change the postmaster's copy.)
	 */
	split_opts(av, &ac, ExtraOptions);

	/* Tell the backend what protocol the frontend is using. */
	sprintf(protobuf, "-v%u", port->proto);
	av[ac++] = protobuf;

	/*
	 * Tell the backend it is being called from the postmaster, and which
	 * database to use.  -p marks the end of secure switches.
	 */
	av[ac++] = "-p";

	StrNCpy(dbbuf, port->database, ARGV_SIZE);
	av[ac++] = dbbuf;

	/*
	 * Pass the (insecure) option switches from the connection request.
	 */
	StrNCpy(optbuf, port->options, ARGV_SIZE);
	split_opts(av, &ac, optbuf);

	/*
	 * Pass the (insecure) debug output file request.
	 *
	 * NOTE: currently, this is useless code, since the backend will not
	 * honor an insecure -o switch.  I left it here since the backend
	 * could be modified to allow insecure -o, given adequate checking
	 * that the specified filename is something safe to write on.
	 */
	if (port->tty[0])
	{
		StrNCpy(ttybuf, port->tty, ARGV_SIZE);
		av[ac++] = "-o";
		av[ac++] = ttybuf;
	}

	av[ac] = (char *) NULL;

	if (DebugLvl > 1)
	{
		fprintf(stderr, "%s child[%d]: starting with (",
				progname, MyProcPid);
		for (i = 0; i < ac; ++i)
			fprintf(stderr, "%s ", av[i]);
		fprintf(stderr, ")\n");
	}

	return (PostgresMain(ac, av, real_argc, real_argv));
}

/*
 * ExitPostmaster -- cleanup
 */
static void
ExitPostmaster(int status)
{
	/* should cleanup shared memory and kill all backends */

	/*
	 * Not sure of the semantics here.	When the Postmaster dies, should
	 * the backends all be killed? probably not.
	 */
	if (ServerSock_INET != INVALID_SOCK)
		StreamClose(ServerSock_INET);
#ifndef __CYGWIN32__
	if (ServerSock_UNIX != INVALID_SOCK)
		StreamClose(ServerSock_UNIX);
#endif
	proc_exit(status);
}

static void
dumpstatus(SIGNAL_ARGS)
{
	Dlelem	   *curr = DLGetHead(PortList);

	while (curr)
	{
		Port	   *port = DLE_VAL(curr);

		fprintf(stderr, "%s: dumpstatus:\n", progname);
		fprintf(stderr, "\tsock %d\n", port->sock);
		curr = DLGetSucc(curr);
	}
}

/*
 * CharRemap
 */
static char
CharRemap(long int ch)
{

	if (ch < 0)
		ch = -ch;

	ch = ch % 62;
	if (ch < 26)
		return 'A' + ch;

	ch -= 26;
	if (ch < 26)
		return 'a' + ch;

	ch -= 26;
	return '0' + ch;
}

/*
 * RandomSalt
 */
static void
RandomSalt(char *salt)
{
	long		rand = PostmasterRandom();

	*salt = CharRemap(rand % 62);
	*(salt + 1) = CharRemap(rand / 62);
}

/*
 * PostmasterRandom
 */
static long
PostmasterRandom(void)
{

	static bool initialized = false;

	if (!initialized)
	{
		Assert(random_seed != 0 && !IsUnderPostmaster);
		srandom(random_seed);
		initialized = true;
	}

	return random() ^ random_seed;
}

/*
 * Count up number of child processes.
 */
static int
CountChildren(void)
{
	Dlelem	   *curr;
	Backend    *bp;
	int			mypid = getpid();
	int			cnt = 0;

	for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
	{
		bp = (Backend *) DLE_VAL(curr);
		if (bp->pid != mypid)
			cnt++;
	}
	return cnt;
}