/*
 * set backend connection close timer
 */
void pool_connection_pool_timer(POOL_CONNECTION_POOL *backend)
{
	POOL_CONNECTION_POOL *p = pool_connection_pool;
	int i;

	pool_debug("pool_connection_pool_timer: set close time %ld", time(NULL));

	MASTER_CONNECTION(backend)->closetime = time(NULL);		/* set connection close time */

	if (pool_config->connection_life_time == 0)
		return;

	/* look for any other timeout */
	for (i=0;i<pool_config->max_pool;i++, p++)
	{
		if (!MASTER_CONNECTION(p))
			continue;
		if (!MASTER_CONNECTION(p)->sp)
			continue;
		if (MASTER_CONNECTION(p)->sp->user == NULL)
			continue;

		if (p != backend && MASTER_CONNECTION(p)->closetime)
			return;
	}

	/* no other timer found. set my timer */
	pool_debug("pool_connection_pool_timer: set alarm after %d seconds", pool_config->connection_life_time);
	pool_signal(SIGALRM, pool_backend_timer_handler);
	alarm(pool_config->connection_life_time);
}
void pool_backend_timer(void)
{
#define TMINTMAX 0x7fffffff

	POOL_CONNECTION_POOL *p = pool_connection_pool;
	int i, j;
	time_t now;
	time_t nearest = TMINTMAX;
	ConnectionInfo *info;

	POOL_SETMASK(&BlockSig);

	now = time(NULL);

	pool_debug("pool_backend_timer_handler called at %ld", now);

	for (i=0;i<pool_config->max_pool;i++, p++)
	{
		if (!MASTER_CONNECTION(p))
			continue;
		if (!MASTER_CONNECTION(p)->sp)
			continue;
		if (MASTER_CONNECTION(p)->sp->user == NULL)
			continue;

		/* timer expire? */
		if (MASTER_CONNECTION(p)->closetime)
		{
			int freed = 0;

			pool_debug("pool_backend_timer_handler: expire time: %ld",
					   MASTER_CONNECTION(p)->closetime+pool_config->connection_life_time);

			if (now >= (MASTER_CONNECTION(p)->closetime+pool_config->connection_life_time))
			{
				/* discard expired connection */
				pool_debug("pool_backend_timer_handler: expires user %s database %s",
						   MASTER_CONNECTION(p)->sp->user, MASTER_CONNECTION(p)->sp->database);

				pool_send_frontend_exits(p);

				for (j=0;j<NUM_BACKENDS;j++)
				{
					if (!VALID_BACKEND(j))
						continue;

					if (!freed)
					{
						pool_free_startup_packet(CONNECTION_SLOT(p, j)->sp);
						freed = 1;
					}

					pool_close(CONNECTION(p, j));
					free(CONNECTION_SLOT(p, j));
				}
				info = p->info;
				memset(p, 0, sizeof(POOL_CONNECTION_POOL));
				p->info = info;
				memset(p->info, 0, sizeof(ConnectionInfo) * MAX_NUM_BACKENDS);

				/* prepare to shutdown connections to system db */
				if(pool_config->system_db_dynamic_connection && (pool_config->parallel_mode || pool_config->enable_query_cache))
				{
					if (system_db_info->pgconn)
						pool_close_libpq_connection();
					if (pool_system_db_connection() && pool_system_db_connection()->con)
					{
						pool_send_frontend_exit(pool_system_db_connection()->con);
						pool_close(pool_system_db_connection()->con);
					}

					if( system_db_info->connection )
					{
						free( system_db_info->connection );
						memset(system_db_info->connection, 0, sizeof(POOL_CONNECTION_POOL_SLOT));
						system_db_info->connection = NULL;
					}
				}
			}
			else
			{
				/* look for nearest timer */
				if (MASTER_CONNECTION(p)->closetime < nearest)
					nearest = MASTER_CONNECTION(p)->closetime;
			}
		}
	}

	/* any remaining timer */
	if (nearest != TMINTMAX)
	{
		nearest = pool_config->connection_life_time - (now - nearest);
		if (nearest <= 0)
		  nearest = 1;
		pool_signal(SIGALRM, pool_backend_timer_handler);
		alarm(nearest);
	}

	POOL_SETMASK(&UnBlockSig);
}
Example #3
0
/*
* Read startup packet
*
* Read the startup packet and parse the contents.
*/
static StartupPacket *read_startup_packet(POOL_CONNECTION *cp)
{
	StartupPacket *sp;
	StartupPacket_v2 *sp2;
	int protov;
	int len;
	char *p;

	sp = (StartupPacket *)calloc(sizeof(*sp), 1);
	if (!sp)
	{
		pool_error("read_startup_packet: out of memory");
		return NULL;
	}

	if (pool_config->authentication_timeout > 0)
	{
		pool_signal(SIGALRM, authentication_timeout);
		alarm(pool_config->authentication_timeout);
	}

	/* read startup packet length */
	if (pool_read(cp, &len, sizeof(len)))
	{
		pool_error("read_startup_packet: incorrect packet length (%d)", len);
		pool_free_startup_packet(sp);
		alarm(0);
		pool_signal(SIGALRM, SIG_IGN);
		return NULL;
	}
	len = ntohl(len);
	len -= sizeof(len);

	if (len <= 0 || len >= MAX_STARTUP_PACKET_LENGTH)
	{
		pool_error("read_startup_packet: incorrect packet length (%d)", len);
		pool_free_startup_packet(sp);
		alarm(0);
		pool_signal(SIGALRM, SIG_IGN);
		return NULL;
	}

	sp->startup_packet = calloc(len, 1);
	if (!sp->startup_packet)
	{
		pool_error("read_startup_packet: out of memory");
		pool_free_startup_packet(sp);
		alarm(0);
		pool_signal(SIGALRM, SIG_IGN);
		return NULL;
	}

	/* read startup packet */
	if (pool_read(cp, sp->startup_packet, len))
	{
		pool_free_startup_packet(sp);
		alarm(0);
		pool_signal(SIGALRM, SIG_IGN);
		return NULL;
	}

	sp->len = len;
	memcpy(&protov, sp->startup_packet, sizeof(protov));
	sp->major = ntohl(protov)>>16;
	sp->minor = ntohl(protov) & 0x0000ffff;
	p = sp->startup_packet;

	switch(sp->major)
	{
		case PROTO_MAJOR_V2: /* V2 */
			sp2 = (StartupPacket_v2 *)(sp->startup_packet);

			sp->database = calloc(SM_DATABASE+1, 1);
			if (!sp->database)
			{
				pool_error("read_startup_packet: out of memory");
				pool_free_startup_packet(sp);
				alarm(0);
				pool_signal(SIGALRM, SIG_IGN);
				return NULL;
			}
			strncpy(sp->database, sp2->database, SM_DATABASE);

			sp->user = calloc(SM_USER+1, 1);
			if (!sp->user)
			{
				pool_error("read_startup_packet: out of memory");
				pool_free_startup_packet(sp);
				alarm(0);
				pool_signal(SIGALRM, SIG_IGN);
				return NULL;
			}
			strncpy(sp->user, sp2->user, SM_USER);

			break;

		case PROTO_MAJOR_V3: /* V3 */
			p += sizeof(int);	/* skip protocol version info */

			while(*p)
			{
				if (!strcmp("user", p))
				{
					p += (strlen(p) + 1);
					sp->user = strdup(p);
					if (!sp->user)
					{
						pool_error("read_startup_packet: out of memory");
						pool_free_startup_packet(sp);
						alarm(0);
						pool_signal(SIGALRM, SIG_IGN);
						return NULL;
					}
				}
				else if (!strcmp("database", p))
				{
					p += (strlen(p) + 1);
					sp->database = strdup(p);
					if (!sp->database)
					{
						pool_error("read_startup_packet: out of memory");
						pool_free_startup_packet(sp);
						alarm(0);
						pool_signal(SIGALRM, SIG_IGN);
						return NULL;
					}
				}

				/*
				 * From 9.0, the start up packet may include
				 * application name. After receiving such that packet,
				 * backend sends parameter status of application_name.
				 * Upon reusing connection to backend, we need to
				 * emulate this behavior of backend. So we remember
				 * this and send parameter status packet to frontend
				 * instead of backend in
				 * connect_using_existing_connection().
				 */
				else if (!strcmp("application_name", p))
				{
					p += (strlen(p) + 1);
					sp->application_name = p;
					pool_debug("read_startup_packet: application_name: %s", p);
				}

				p += (strlen(p) + 1);
			}
			break;

		case 1234:		/* cancel or SSL request */
			/* set dummy database, user info */
			sp->database = calloc(1, 1);
			if (!sp->database)
			{
				pool_error("read_startup_packet: out of memory");
				pool_free_startup_packet(sp);
				alarm(0);
				pool_signal(SIGALRM, SIG_IGN);
				return NULL;
			}
			sp->user = calloc(1, 1);
			if (!sp->user)
			{
				pool_error("read_startup_packet: out of memory");
				pool_free_startup_packet(sp);
				alarm(0);
				pool_signal(SIGALRM, SIG_IGN);
				return NULL;
			}
			break;

		default:
			pool_error("read_startup_packet: invalid major no: %d", sp->major);
			pool_free_startup_packet(sp);
			alarm(0);
			pool_signal(SIGALRM, SIG_IGN);
			return NULL;
	}

	pool_debug("Protocol Major: %d Minor: %d database: %s user: %s",
			   sp->major, sp->minor, sp->database, sp->user);
	alarm(0);
	pool_signal(SIGALRM, SIG_IGN);
	return sp;
}
Example #4
0
/*
 * fork escalation process
 */
pid_t
fork_escalation_process(void)
{
	pid_t		pid;

	pid = fork();
	if (pid != 0)
	{
		if (pid == -1)
			ereport(NOTICE,
					(errmsg("failed to fork a escalation process")));
		return pid;
	}
	on_exit_reset();
	processType = PT_WATCHDOG_UTILITY;

	POOL_SETMASK(&UnBlockSig);

	init_ps_display("", "", "", "");

	pool_signal(SIGTERM, wd_exit);
	pool_signal(SIGINT, wd_exit);
	pool_signal(SIGQUIT, wd_exit);
	pool_signal(SIGCHLD, SIG_DFL);
	pool_signal(SIGHUP, SIG_IGN);
	pool_signal(SIGPIPE, SIG_IGN);

	MemoryContextSwitchTo(TopMemoryContext);

	set_ps_display("watchdog escalation", false);

	ereport(LOG,
			(errmsg("watchdog: escalation started")));

	/*
	 * STEP 1 clear shared memory cache
	 */
	if (pool_config->memory_cache_enabled && pool_is_shmem_cache() &&
		pool_config->clear_memqcache_on_escalation)
	{
		ereport(LOG,
				(errmsg("watchdog escalation"),
				 errdetail("clearing all the query cache on shared memory")));

		pool_clear_memory_cache();
	}

	/*
	 * STEP 2 execute escalation command provided by user in pgpool conf file
	 */
	if (strlen(pool_config->wd_escalation_command))
	{
		int			r = system(pool_config->wd_escalation_command);

		if (WIFEXITED(r))
		{
			if (WEXITSTATUS(r) == EXIT_SUCCESS)
				ereport(LOG,
						(errmsg("watchdog escalation successful")));
			else
			{
				ereport(WARNING,
						(errmsg("watchdog escalation command failed with exit status: %d", WEXITSTATUS(r))));
			}
		}
		else
		{
			ereport(WARNING,
					(errmsg("watchdog escalation command exit abnormally")));
		}
	}

	/*
	 * STEP 3 bring up the delegate IP
	 */
	if (strlen(pool_config->delegate_IP) != 0)
	{
		if (wd_IP_up() != WD_OK)
			ereport(WARNING,
					(errmsg("watchdog escalation failed to acquire delegate IP")));

	}
	exit(0);
}
Example #5
0
/*
 * fork de-escalation process
 */
pid_t
fork_plunging_process(void)
{
	pid_t		pid;

	pid = fork();
	if (pid != 0)
	{
		if (pid == -1)
			ereport(NOTICE,
					(errmsg("failed to fork a de-escalation process")));
		return pid;
	}
	on_exit_reset();
	processType = PT_WATCHDOG_UTILITY;

	POOL_SETMASK(&UnBlockSig);

	init_ps_display("", "", "", "");

	pool_signal(SIGTERM, wd_exit);
	pool_signal(SIGINT, wd_exit);
	pool_signal(SIGQUIT, wd_exit);
	pool_signal(SIGCHLD, SIG_DFL);
	pool_signal(SIGHUP, SIG_IGN);
	pool_signal(SIGPIPE, SIG_IGN);

	MemoryContextSwitchTo(TopMemoryContext);

	set_ps_display("watchdog de-escalation", false);

	ereport(LOG,
			(errmsg("watchdog: de-escalation started")));

	/*
	 * STEP 1 execute de-escalation command provided by user in pgpool conf
	 * file
	 */
	if (strlen(pool_config->wd_de_escalation_command))
	{
		int			r = system(pool_config->wd_de_escalation_command);

		if (WIFEXITED(r))
		{
			if (WEXITSTATUS(r) == EXIT_SUCCESS)
				ereport(LOG,
						(errmsg("watchdog de-escalation successful")));
			else
			{
				ereport(WARNING,
						(errmsg("watchdog de-escalation command failed with exit status: %d", WEXITSTATUS(r))));
			}
		}
		else
		{
			ereport(WARNING,
					(errmsg("watchdog de-escalation command exit abnormally")));
		}
	}

	/*
	 * STEP 2 bring down the delegate IP
	 */

	if (strlen(pool_config->delegate_IP) != 0)
	{
		if (wd_IP_down() != WD_OK)
			ereport(WARNING,
					(errmsg("watchdog de-escalation failed to bring down delegate IP")));
	}
	exit(0);
}
Example #6
0
void pool_backend_timer(void)
{
#define TMINTMAX 0x7fffffff

	POOL_CONNECTION_POOL *p = pool_connection_pool;
	int i;
	time_t now;
	time_t nearest = TMINTMAX;

	POOL_SETMASK(&BlockSig);

	now = time(NULL);

	pool_debug("pool_backend_timer_handler called at %d", now);

	for (i=0;i<pool_config.max_pool;i++, p++)
	{
		if (!MASTER_CONNECTION(p))
			continue;
		if (MASTER_CONNECTION(p)->sp->user == NULL)
			continue;

		/* timer expire? */
		if (MASTER_CONNECTION(p)->closetime)
		{
			pool_debug("pool_backend_timer_handler: expire time: %d",
					   MASTER_CONNECTION(p)->closetime+pool_config.connection_life_time);

			if (now >= (MASTER_CONNECTION(p)->closetime+pool_config.connection_life_time))
			{
				/* discard expired connection */
				pool_debug("pool_backend_timer_handler: expires user %s database %s", MASTER_CONNECTION(p)->sp->user, MASTER_CONNECTION(p)->sp->database);

				pool_send_frontend_exits(p);

				pool_free_startup_packet(MASTER_CONNECTION(p)->sp);
				pool_close(MASTER_CONNECTION(p)->con);
				free(MASTER_CONNECTION(p));

				if (DUAL_MODE)
				{
					pool_close(SECONDARY_CONNECTION(p)->con);
					free(SECONDARY_CONNECTION(p));
				}

				memset(p, 0, sizeof(POOL_CONNECTION_POOL));
			}
			else
			{
				/* look for nearest timer */
				if (MASTER_CONNECTION(p)->closetime < nearest)
					nearest = MASTER_CONNECTION(p)->closetime;
			}
		}
	}

	/* any remaining timer */
	if (nearest != TMINTMAX)
	{
		nearest = pool_config.connection_life_time - (now - nearest);
		if (nearest <= 0)
		  nearest = 1;
		pool_signal(SIGALRM, pool_backend_timer_handler);
		alarm(nearest);
	}

	POOL_SETMASK(&UnBlockSig);
}
Example #7
0
/*
* pgpool main program
*/
int main(int argc, char **argv)
{
	int opt;
	int i;
	int pid;
	int size;
	int retrycnt;
	int sys_retrycnt;

	myargc = argc;
	myargv = argv;

	snprintf(conf_file, sizeof(conf_file), "%s/%s", DEFAULT_CONFIGDIR, POOL_CONF_FILE_NAME);
	snprintf(pcp_conf_file, sizeof(pcp_conf_file), "%s/%s", DEFAULT_CONFIGDIR, PCP_PASSWD_FILE_NAME);
	snprintf(hba_file, sizeof(hba_file), "%s/%s", DEFAULT_CONFIGDIR, HBA_CONF_FILE_NAME);

	while ((opt = getopt(argc, argv, "a:cdf:F:hm:nv")) != -1)
	{
		switch (opt)
		{
			case 'a':    /* specify hba configuration file */
				if (!optarg)
				{
					usage();
					exit(1);
				}
				strncpy(hba_file, optarg, sizeof(hba_file));
				break;

			case 'c':			/* clear cache option */
				clear_cache = 1;
				break;

			case 'd':	/* debug option */
				debug = 1;
				break;

			case 'f':	/* specify configuration file */
				if (!optarg)
				{
					usage();
					exit(1);
				}
				strncpy(conf_file, optarg, sizeof(conf_file));
				break;

			case 'F':   /* specify PCP password file */
				if (!optarg)
				{
					usage();
					exit(1);
				}
				strncpy(pcp_conf_file, optarg, sizeof(pcp_conf_file));
				break;

			case 'h':
				usage();
				exit(0);
				break;

			case 'm':	/* stop mode */
				if (!optarg)
				{
					usage();
					exit(1);
				}
				if (*optarg == 's' || !strcmp("smart", optarg))
					stop_sig = SIGTERM;		/* smart shutdown */
				else if (*optarg == 'f' || !strcmp("fast", optarg))
					stop_sig = SIGINT;		/* fast shutdown */
				else if (*optarg == 'i' || !strcmp("immediate", optarg))
					stop_sig = SIGQUIT;		/* immediate shutdown */
				else
				{
					usage();
					exit(1);
				}
				break;

			case 'n':	/* no detaching control ttys */
				not_detach = 1;
				break;

			case 'v':
				show_version();
				exit(0);

			default:
				usage();
				exit(1);
		}
	}

	mypid = getpid();

	if (pool_init_config())
		exit(1);

	if (pool_get_config(conf_file, INIT_CONFIG))
	{
		pool_error("Unable to get configuration. Exiting...");
		exit(1);
	}

	if (pool_config->enable_pool_hba)
		load_hba(hba_file);

	/*
	 * If a non-switch argument remains, then it should be either "reload" or "stop".
	 */
	if (optind == (argc - 1))
	{
		if (!strcmp(argv[optind], "reload"))
		{
				pid_t pid;

				pid = read_pid_file();
				if (pid < 0)
				{
					pool_error("could not read pid file");
					pool_shmem_exit(1);
					exit(1);
				}

				if (kill(pid, SIGHUP) == -1)
				{
					pool_error("could not reload configuration file pid: %d. reason: %s", pid, strerror(errno));
					pool_shmem_exit(1);
					exit(1);
				}
				pool_shmem_exit(0);
				exit(0);
		}
		if (!strcmp(argv[optind], "stop"))
		{
			stop_me();
			pool_shmem_exit(0);
			exit(0);
		}
		else
		{
			usage();
			pool_shmem_exit(1);
			exit(1);
		}
	}
	/*
	 * else if no non-switch argument remains, then it should be a start request
	 */
	else if (optind == argc)
	{
		pid = read_pid_file();
		if (pid > 0)
		{
			if (kill(pid, 0) == 0)
			{
				fprintf(stderr, "pid file found. is another pgpool(%d) is running?\n", pid);
				exit(1);
			}
			else
				fprintf(stderr, "pid file found but it seems bogus. Trying to start pgpool anyway...\n");
		}
	}
	/*
	 * otherwise an error...
	 */
	else
	{
		usage();
		exit(1);
	}

	/* set signal masks */
	poolinitmask();

	if (not_detach)
		write_pid_file();
	else
		daemonize();

	if (pool_semaphore_create(MAX_NUM_SEMAPHORES))
	{
		pool_error("Unable to create semaphores. Exiting...");
		pool_shmem_exit(1);
		exit(1);
	}

	/*
	 * Restore previous backend status if possible
	 */
	read_status_file();

	/* clear cache */
	if (clear_cache && pool_config->enable_query_cache && SYSDB_STATUS == CON_UP)
	{
		Interval interval[1];

		interval[0].quantity = 0;
		interval[0].unit = second;

		pool_clear_cache_by_time(interval, 1);
	}

	/* set unix domain socket path */
	snprintf(un_addr.sun_path, sizeof(un_addr.sun_path), "%s/.s.PGSQL.%d",
			 pool_config->socket_dir,
			 pool_config->port);

	/* set up signal handlers */
	pool_signal(SIGPIPE, SIG_IGN);

	/* create unix domain socket */
	unix_fd = create_unix_domain_socket(un_addr);

	/* create inet domain socket if any */
	if (pool_config->listen_addresses[0])
	{
		inet_fd = create_inet_domain_socket(pool_config->listen_addresses, pool_config->port);
	}

	size = pool_config->num_init_children * pool_config->max_pool * sizeof(ConnectionInfo);
	con_info = pool_shared_memory_create(size);
	if (con_info == NULL)
	{
		pool_error("failed to allocate connection informations");
		myexit(1);
	}
	memset(con_info, 0, size);

	size = pool_config->num_init_children * (sizeof(ProcessInfo));
	pids = pool_shared_memory_create(size);
	if (pids == NULL)
	{
		pool_error("failed to allocate pids");
		myexit(1);
	}
	memset(pids, 0, size);
	for (i = 0; i < pool_config->num_init_children; i++)
	{
		pids[i].connection_info = &con_info[i * pool_config->max_pool];
	}

	/* create fail over/switch over event area */
	Req_info = pool_shared_memory_create(sizeof(POOL_REQUEST_INFO));
	if (Req_info == NULL)
	{
		pool_error("failed to allocate Req_info");
		myexit(1);
	}

	/* initialize Req_info */
	Req_info->kind = NODE_UP_REQUEST;
	memset(Req_info->node_id, -1, sizeof(int) * MAX_NUM_BACKENDS);
	Req_info->master_node_id = get_next_master_node();
	Req_info->conn_counter = 0;

	InRecovery = pool_shared_memory_create(sizeof(int));
	if (InRecovery == NULL)
	{
		pool_error("failed to allocate InRecovery");
		myexit(1);
	}
	*InRecovery = 0;

	/*
	 * We need to block signal here. Otherwise child might send some
	 * signals, for example SIGUSR1(fail over).  Children will inherit
	 * signal blocking but they do unblock signals at the very beginning
	 * of process.  So this is harmless.
	 */
	POOL_SETMASK(&BlockSig);

	/* fork the children */
	for (i=0;i<pool_config->num_init_children;i++)
	{
		pids[i].pid = fork_a_child(unix_fd, inet_fd, i);
		pids[i].start_time = time(NULL);
	}

	/* set up signal handlers */

	pool_signal(SIGTERM, exit_handler);
	pool_signal(SIGINT, exit_handler);
	pool_signal(SIGQUIT, exit_handler);
	pool_signal(SIGCHLD, reap_handler);
	pool_signal(SIGUSR1, failover_handler);
	pool_signal(SIGUSR2, wakeup_handler);
	pool_signal(SIGHUP, reload_config_handler);

	/* create pipe for delivering event */
	if (pipe(pipe_fds) < 0)
	{
		pool_error("failed to create pipe");
		myexit(1);
	}

	pool_log("pgpool successfully started");

	/* fork a child for PCP handling */
	snprintf(pcp_un_addr.sun_path, sizeof(pcp_un_addr.sun_path), "%s/.s.PGSQL.%d",
			 pool_config->pcp_socket_dir,
			 pool_config->pcp_port);
	pcp_unix_fd = create_unix_domain_socket(pcp_un_addr);
    /* maybe change "*" to pool_config->pcp_listen_addresses */
	pcp_inet_fd = create_inet_domain_socket("*", pool_config->pcp_port);
	pcp_pid = pcp_fork_a_child(pcp_unix_fd, pcp_inet_fd, pcp_conf_file);

	retrycnt = 0;		/* reset health check retry counter */
	sys_retrycnt = 0;	/* reset SystemDB health check retry counter */

	/*
	 * This is the main loop
	 */
	for (;;)
	{
		CHECK_REQUEST;

		/* do we need health checking for PostgreSQL? */
		if (pool_config->health_check_period > 0)
		{
			int sts;
			int sys_sts = 0;
			unsigned int sleep_time;

			if (retrycnt == 0)
			{
				pool_debug("starting health checking");
			}
			else
			{
				pool_debug("retrying %d th health checking", retrycnt);
			}

			if (pool_config->health_check_timeout > 0)
			{
				/*
				 * set health checker timeout. we want to detect
				 * communication path failure much earlier before
				 * TCP/IP stack detects it.
				 */
				pool_signal(SIGALRM, health_check_timer_handler);
				alarm(pool_config->health_check_timeout);
			}

			/*
			 * do actual health check. trying to connect to the backend
			 */
			errno = 0;
			health_check_timer_expired = 0;
			POOL_SETMASK(&UnBlockSig);
			sts = health_check();
			POOL_SETMASK(&BlockSig);
			if (pool_config->parallel_mode || pool_config->enable_query_cache)
				sys_sts = system_db_health_check();

			if ((sts > 0 || sys_sts < 0) && (errno != EINTR || (errno == EINTR && health_check_timer_expired)))
			{
				if (sts > 0)
				{
					sts--;

					if (!pool_config->parallel_mode)
					{
						pool_log("set %d th backend down status", sts);
						Req_info->kind = NODE_DOWN_REQUEST;
						Req_info->node_id[0] = sts;
						failover();
						/* need to distribute this info to children */
					}
					else
					{
						retrycnt++;
						pool_signal(SIGALRM, SIG_IGN);	/* Cancel timer */

						if (retrycnt > NUM_BACKENDS)
						{
							/* retry count over */
							pool_log("set %d th backend down status", sts);
							Req_info->kind = NODE_DOWN_REQUEST;
							Req_info->node_id[0] = sts;
							failover();
							retrycnt = 0;
						}
						else
						{
							/* continue to retry */
							sleep_time = pool_config->health_check_period/NUM_BACKENDS;
							pool_debug("retry sleep time: %d seconds", sleep_time);
							pool_sleep(sleep_time);
							continue;
						}
					}
				}
				if (sys_sts < 0)
				{
					sys_retrycnt++;
					pool_signal(SIGALRM, SIG_IGN);

					if (sys_retrycnt > NUM_BACKENDS)
					{
						pool_log("set SystemDB down status");
						SYSDB_STATUS = CON_DOWN;
						sys_retrycnt = 0;
					}
					else if (sts == 0) /* goes to sleep only when SystemDB alone was down */
					{
						sleep_time = pool_config->health_check_period/NUM_BACKENDS;
						pool_debug("retry sleep time: %d seconds", sleep_time);
						pool_sleep(sleep_time);
						continue;
					}
				}
			}

			if (pool_config->health_check_timeout > 0)
			{
				/* seems ok. cancel health check timer */
				pool_signal(SIGALRM, SIG_IGN);
			}

			sleep_time = pool_config->health_check_period;
			pool_sleep(sleep_time);
		}
		else
		{
			for (;;)
			{
				int r;
				struct timeval t = {3, 0};

				POOL_SETMASK(&UnBlockSig);
				r = pool_pause(&t);
				POOL_SETMASK(&BlockSig);
				if (r > 0)
					break;
			}
		}
	}

	pool_shmem_exit(0);
}