postmaster.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

		while (offset < len)
		{
			char	   *nameptr = ((char *) buf) + offset;
			int32		valoffset;
			char	   *valptr;

			if (*nameptr == '\0')
				break;			/* found packet terminator */
			valoffset = offset + strlen(nameptr) + 1;
			if (valoffset >= len)
				break;			/* missing value, will complain below */
			valptr = ((char *) buf) + valoffset;

			if (strcmp(nameptr, "database") == 0)
				port->database_name = pstrdup(valptr);
			else if (strcmp(nameptr, "user") == 0)
				port->user_name = pstrdup(valptr);
			else if (strcmp(nameptr, "options") == 0)
				port->cmdline_options = pstrdup(valptr);
			else
			{
				/* Assume it's a generic GUC option */
				port->guc_options = lappend(port->guc_options,
											pstrdup(nameptr));
				port->guc_options = lappend(port->guc_options,
											pstrdup(valptr));
			}
			offset = valoffset + strlen(valptr) + 1;
		}

		/*
		 * If we didn't find a packet terminator exactly at the end of the
		 * given packet length, complain.
		 */
		if (offset != len - 1)
			ereport(FATAL,
					(errcode(ERRCODE_PROTOCOL_VIOLATION),
					 errmsg("invalid startup packet layout: expected terminator as last byte")));
	}
	else
	{
		/*
		 * Get the parameters from the old-style, fixed-width-fields startup
		 * packet as C strings.  The packet destination was cleared first so a
		 * short packet has zeros silently added.  We have to be prepared to
		 * truncate the pstrdup result for oversize fields, though.
		 */
		StartupPacket *packet = (StartupPacket *) buf;

		port->database_name = pstrdup(packet->database);
		if (strlen(port->database_name) > sizeof(packet->database))
			port->database_name[sizeof(packet->database)] = '\0';
		port->user_name = pstrdup(packet->user);
		if (strlen(port->user_name) > sizeof(packet->user))
			port->user_name[sizeof(packet->user)] = '\0';
		port->cmdline_options = pstrdup(packet->options);
		if (strlen(port->cmdline_options) > sizeof(packet->options))
			port->cmdline_options[sizeof(packet->options)] = '\0';
		port->guc_options = NIL;
	}

	/* Check a user name was given. */
	if (port->user_name == NULL || port->user_name[0] == '\0')
		ereport(FATAL,
				(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
			 errmsg("no PostgreSQL user name specified in startup packet")));

	/* The database defaults to the user name. */
	if (port->database_name == NULL || port->database_name[0] == '\0')
		port->database_name = pstrdup(port->user_name);

	if (Db_user_namespace)
	{
		/*
		 * If user@, it is a global user, remove '@'. We only want to do this
		 * if there is an '@' at the end and no earlier in the user string or
		 * they may fake as a local user of another database attaching to this
		 * database.
		 */
		if (strchr(port->user_name, '@') ==
			port->user_name + strlen(port->user_name) - 1)
			*strchr(port->user_name, '@') = '\0';
		else
		{
			/* Append '@' and dbname */
			char	   *db_user;

			db_user = palloc(strlen(port->user_name) +
							 strlen(port->database_name) + 2);
			sprintf(db_user, "%s@%s", port->user_name, port->database_name);
			port->user_name = db_user;
		}
	}

	/*
	 * Truncate given database and user names to length of a Postgres name.
	 * This avoids lookup failures when overlength names are given.
	 */
	if (strlen(port->database_name) >= NAMEDATALEN)
		port->database_name[NAMEDATALEN - 1] = '\0';
	if (strlen(port->user_name) >= NAMEDATALEN)
		port->user_name[NAMEDATALEN - 1] = '\0';

	/*
	 * Done putting stuff in TopMemoryContext.
	 */
	MemoryContextSwitchTo(oldcontext);

	/*
	 * If we're going to reject the connection due to database state, say so
	 * now instead of wasting cycles on an authentication exchange. (This also
	 * allows a pg_ping utility to be written.)
	 */
	switch (port->canAcceptConnections)
	{
		case CAC_STARTUP:
			ereport(FATAL,
					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
					 errmsg("the database system is starting up")));
			break;
		case CAC_SHUTDOWN:
			ereport(FATAL,
					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
					 errmsg("the database system is shutting down")));
			break;
		case CAC_RECOVERY:
			ereport(FATAL,
					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
					 errmsg("the database system is in recovery mode")));
			break;
		case CAC_TOOMANY:
			ereport(FATAL,
					(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
					 errmsg("sorry, too many clients already")));
			break;
		case CAC_OK:
		default:
			break;
	}

	return STATUS_OK;
}


/*
 * The client has sent a cancel request packet, not a normal
 * start-a-new-connection packet.  Perform the necessary processing.
 * Nothing is sent back to the client.
 */
static void
processCancelRequest(Port *port, void *pkt)
{
	CancelRequestPacket *canc = (CancelRequestPacket *) pkt;
	int			backendPID;
	long		cancelAuthCode;
	Backend    *bp;

#ifndef EXEC_BACKEND
	Dlelem	   *curr;
#else
	int			i;
#endif

	backendPID = (int) ntohl(canc->backendPID);
	cancelAuthCode = (long) ntohl(canc->cancelAuthCode);

	/*
	 * See if we have a matching backend.  In the EXEC_BACKEND case, we can no
	 * longer access the postmaster's own backend list, and must rely on the
	 * duplicate array in shared memory.
	 */
#ifndef EXEC_BACKEND
	for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
	{
		bp = (Backend *) DLE_VAL(curr);
#else
	for (i = 0; i < NUM_BACKENDARRAY_ELEMS; i++)
	{
		bp = (Backend *) &ShmemBackendArray[i];
#endif
		if (bp->pid == backendPID)
		{
			if (bp->cancel_key == cancelAuthCode)
			{
				/* Found a match; signal that backend to cancel current op */
				ereport(DEBUG2,
						(errmsg_internal("processing cancel request: sending SIGINT to process %d",
										 backendPID)));
				kill(bp->pid, SIGINT);
			}
			else
				/* Right PID, wrong key: no way, Jose */
				ereport(DEBUG2,
				 (errmsg_internal("bad key in cancel request for process %d",
								  backendPID)));
			return;
		}
	}

	/* No matching backend */
	ereport(DEBUG2,
			(errmsg_internal("bad pid in cancel request for process %d",
							 backendPID)));
}

/*
 * canAcceptConnections --- check to see if database state allows connections.
 */
static enum CAC_state
canAcceptConnections(void)
{
	/* Can't start backends when in startup/shutdown/recovery state. */
	if (Shutdown > NoShutdown)
		return CAC_SHUTDOWN;
	if (StartupPID)
		return CAC_STARTUP;
	if (FatalError)
		return CAC_RECOVERY;

	/*
	 * Don't start too many children.
	 *
	 * We allow more connections than we can have backends here because some
	 * might still be authenticating; they might fail auth, or some existing
	 * backend might exit before the auth cycle is completed. The exact
	 * MaxBackends limit is enforced when a new backend tries to join the
	 * shared-inval backend array.
	 */
	if (CountChildren() >= 2 * MaxBackends)
		return CAC_TOOMANY;

	return CAC_OK;
}


/*
 * ConnCreate -- create a local connection data structure
 */
static Port *
ConnCreate(int serverFd)
{
	Port	   *port;

	if (!(port = (Port *) calloc(1, sizeof(Port))))
	{
		ereport(LOG,
				(errcode(ERRCODE_OUT_OF_MEMORY),
				 errmsg("out of memory")));
		ExitPostmaster(1);
	}

	if (StreamConnection(serverFd, port) != STATUS_OK)
	{
		StreamClose(port->sock);
		ConnFree(port);
		port = NULL;
	}
	else
	{
		/*
		 * Precompute password salt values to use for this connection. It's
		 * slightly annoying to do this long in advance of knowing whether
		 * we'll need 'em or not, but we must do the random() calls before we
		 * fork, not after.  Else the postmaster's random sequence won't get
		 * advanced, and all backends would end up using the same salt...
		 */
		RandomSalt(port->cryptSalt, port->md5Salt);
	}

	return port;
}


/*
 * ConnFree -- free a local connection data structure
 */
static void
ConnFree(Port *conn)
{
#ifdef USE_SSL
	secure_close(conn);
#endif
	free(conn);
}


/*
 * ClosePostmasterPorts -- close all the postmaster's open sockets
 *
 * This is called during child process startup to release file descriptors
 * that are not needed by that child process.  The postmaster still has
 * them open, of course.
 *
 * Note: we pass am_syslogger as a boolean because we don't want to set
 * the global variable yet when this is called.
 */
void
ClosePostmasterPorts(bool am_syslogger)
{
	int			i;

	/* Close the listen sockets */
	for (i = 0; i < MAXLISTEN; i++)
	{
		if (ListenSocket[i] != -1)
		{
			StreamClose(ListenSocket[i]);
			ListenSocket[i] = -1;
		}
	}

	/* If using syslogger, close the read side of the pipe */
	if (!am_syslogger)
	{
#ifndef WIN32
		if (syslogPipe[0] >= 0)
			close(syslogPipe[0]);
		syslogPipe[0] = -1;
#else
		if (syslogPipe[0])
			CloseHandle(syslogPipe[0]);
		syslogPipe[0] = 0;
#endif
	}
}


/*
 * reset_shared -- reset shared memory and semaphores
 */
static void
reset_shared(int port)
{
	/*
	 * Create or re-create shared memory and semaphores.
	 *
	 * Note: in each "cycle of life" we will normally assign the same IPC keys
	 * (if using SysV shmem and/or semas), since the port number is used to
	 * determine IPC keys.	This helps ensure that we will clean up dead IPC
	 * objects if the postmaster crashes and is restarted.
	 */
	CreateSharedMemoryAndSemaphores(false, port);
}


/*
 * SIGHUP -- reread config files, and tell children to do same
 */
static void
SIGHUP_handler(SIGNAL_ARGS)
{
	int			save_errno = errno;

	PG_SETMASK(&BlockSig);

	if (Shutdown <= SmartShutdown)
	{
		ereport(LOG,
				(errmsg("received SIGHUP, reloading configuration files")));
		ProcessConfigFile(PGC_SIGHUP);
		SignalChildren(SIGHUP);
		if (BgWriterPID != 0)
			kill(BgWriterPID, SIGHUP);
		if (AutoVacPID != 0)
			kill(AutoVacPID, SIGHUP);
		if (PgArchPID != 0)
			kill(PgArchPID, SIGHUP);
		if (SysLoggerPID != 0)
			kill(SysLoggerPID, SIGHUP);
		/* PgStatPID does not currently need SIGHUP */

		/* Reload authentication config files too */
		load_hba();
		load_ident();

#ifdef EXEC_BACKEND
		/* Update the starting-point file for future children */
		write_nondefault_variables(PGC_SIGHUP);
#endif
	}

	PG_SETMASK(&UnBlockSig);

	errno = save_errno;
}


/*
 * pmdie -- signal handler for processing various postmaster signals.
 */
static void
pmdie(SIGNAL_ARGS)
{
	int			save_errno = errno;

	PG_SETMASK(&BlockSig);

	ereport(DEBUG2,
			(errmsg_internal("postmaster received signal %d",
							 postgres_signal_arg)));

	switch (postgres_signal_arg)
	{
		case SIGTERM:

			/*
			 * Smart Shutdown:
			 *
			 * Wait for children to end their work, then shut down.
			 */
			if (Shutdown >= SmartShutdown)
				break;
			Shutdown = SmartShutdown;
			ereport(LOG,
					(errmsg("received smart shutdown request")));

			/*
			 * We won't wait out an autovacuum iteration ...
			 */
			if (AutoVacPID != 0)
			{
				/* Use statement cancel to shut it down */
				kill(AutoVacPID, SIGINT);
				break;			/* let reaper() handle this */
			}

			if (DLGetHead(BackendList))
				break;			/* let reaper() handle this */

			/*
			 * No children left. Begin shutdown of data base system.
			 */
			if (StartupPID != 0 || FatalError)
				break;			/* let reaper() handle this */
			/* Start the bgwriter if not running */
			if (BgWriterPID == 0)
				BgWriterPID = StartBackgroundWriter();
			/* And tell it to shut down */
			if (BgWriterPID != 0)
				kill(BgWriterPID, SIGUSR2);
			/* Tell pgarch to shut down too; nothing left for it to do */
			if (PgArchPID != 0)
				kill(PgArchPID, SIGQUIT);
			/* Tell pgstat to shut down too; nothing left for it to do */
			if (PgStatPID != 0)
				kill(PgStatPID, SIGQUIT);
			break;

		case SIGINT:

			/*
			 * Fast Shutdown:
			 *
			 * Abort all children with SIGTERM (rollback active transactions
			 * and exit) and shut down when they are gone.
			 */
			if (Shutdown >= FastShutdown)
				break;
			Shutdown = FastShutdown;
			ereport(LOG,
					(errmsg("received fast shutdown request")));

			if (DLGetHead(BackendList) || AutoVacPID != 0)
			{
				if (!FatalError)
				{
					ereport(LOG,
							(errmsg("aborting any active transactions")));
					SignalChildren(SIGTERM);
					if (AutoVacPID != 0)
						kill(AutoVacPID, SIGTERM);
					/* reaper() does the rest */
				}
				break;
			}

			/*
			 * No children left. Begin shutdown of data base system.
			 *
			 * Note: if we previously got SIGTERM then we may send SIGUSR2 to
			 * the bgwriter a second time here.  This should be harmless.
			 */
			if (StartupPID != 0 || FatalError)
				break;			/* let reaper() handle this */
			/* Start the bgwriter if not running */
			if (BgWriterPID == 0)
				BgWriterPID = StartBackgroundWriter();
			/* And tell it to shut down */
			if (BgWriterPID != 0)
				kill(BgWriterPID, SIGUSR2);