685 lines
21 KiB
C
685 lines
21 KiB
C
/*
|
|
* Copyright (c) 2016 MariaDB Corporation Ab
|
|
*
|
|
* Use of this software is governed by the Business Source License included
|
|
* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
|
|
*
|
|
* Change Date: 2020-01-01
|
|
*
|
|
* On the date above, in accordance with the Business Source License, use
|
|
* of this software will be governed by version 2 or later of the General
|
|
* Public License.
|
|
*/
|
|
|
|
/**
|
|
* @file mm_mon.c - A Multi-Master Multi Muster cluster monitor
|
|
*/
|
|
|
|
#define MXS_MODULE_NAME "mmmon"
|
|
|
|
#include "mmmon.h"
|
|
#include <maxscale/dcb.h>
|
|
#include <maxscale/alloc.h>
|
|
#include <maxscale/mysql_utils.h>
|
|
|
|
static void monitorMain(void *);
|
|
|
|
/* @see function load_module in load_utils.c for explanation of the following
|
|
* lint directives.
|
|
*/
|
|
/*lint -e14 */
|
|
MXS_MODULE info =
|
|
{
|
|
MXS_MODULE_API_MONITOR,
|
|
MXS_MODULE_BETA_RELEASE,
|
|
MXS_MONITOR_VERSION,
|
|
"A Multi-Master Multi Master monitor",
|
|
"V1.1.1"
|
|
};
|
|
/*lint +e14 */
|
|
|
|
static void *startMonitor(MXS_MONITOR *, const MXS_CONFIG_PARAMETER *);
|
|
static void stopMonitor(MXS_MONITOR *);
|
|
static void diagnostics(DCB *, const MXS_MONITOR *);
|
|
static json_t* diagnostics_json(const MXS_MONITOR *);
|
|
static void detectStaleMaster(void *, int);
|
|
static MXS_MONITOR_SERVERS *get_current_master(MXS_MONITOR *);
|
|
static bool isMySQLEvent(mxs_monitor_event_t event);
|
|
|
|
/**
|
|
* The module entry point routine. It is this routine that
|
|
* must populate the structure that is referred to as the
|
|
* "module object", this is a structure with the set of
|
|
* external entry points for this module.
|
|
*
|
|
* @return The module object
|
|
*/
|
|
MXS_MODULE* MXS_CREATE_MODULE()
|
|
{
|
|
MXS_NOTICE("Initialise the Multi-Master Monitor module.");
|
|
|
|
static MXS_MONITOR_OBJECT MyObject =
|
|
{
|
|
startMonitor,
|
|
stopMonitor,
|
|
diagnostics,
|
|
diagnostics_json
|
|
};
|
|
|
|
static MXS_MODULE info =
|
|
{
|
|
MXS_MODULE_API_MONITOR,
|
|
MXS_MODULE_BETA_RELEASE,
|
|
MXS_MONITOR_VERSION,
|
|
"A Multi-Master Multi Master monitor",
|
|
"V1.1.1",
|
|
MXS_NO_MODULE_CAPABILITIES,
|
|
&MyObject,
|
|
NULL, /* Process init. */
|
|
NULL, /* Process finish. */
|
|
NULL, /* Thread init. */
|
|
NULL, /* Thread finish. */
|
|
{
|
|
{"detect_stale_master", MXS_MODULE_PARAM_BOOL, "false"},
|
|
{
|
|
"script",
|
|
MXS_MODULE_PARAM_PATH,
|
|
NULL,
|
|
MXS_MODULE_OPT_PATH_X_OK
|
|
},
|
|
{
|
|
"events",
|
|
MXS_MODULE_PARAM_ENUM,
|
|
MXS_MONITOR_EVENT_DEFAULT_VALUE,
|
|
MXS_MODULE_OPT_NONE,
|
|
mxs_monitor_event_enum_values
|
|
},
|
|
{MXS_END_MODULE_PARAMS}
|
|
}
|
|
};
|
|
|
|
return &info;
|
|
}
|
|
/*lint +e14 */
|
|
|
|
/**
|
|
* Start the instance of the monitor, returning a handle on the monitor.
|
|
*
|
|
* This function creates a thread to execute the actual monitoring.
|
|
*
|
|
* @param arg The current handle - NULL if first start
|
|
* @return A handle to use when interacting with the monitor
|
|
*/
|
|
static void *
|
|
startMonitor(MXS_MONITOR *mon, const MXS_CONFIG_PARAMETER *params)
|
|
{
|
|
MM_MONITOR *handle = mon->handle;
|
|
|
|
if (handle)
|
|
{
|
|
handle->shutdown = 0;
|
|
MXS_FREE(handle->script);
|
|
}
|
|
else
|
|
{
|
|
if ((handle = (MM_MONITOR *) MXS_MALLOC(sizeof(MM_MONITOR))) == NULL)
|
|
{
|
|
return NULL;
|
|
}
|
|
handle->shutdown = 0;
|
|
handle->id = MXS_MONITOR_DEFAULT_ID;
|
|
handle->master = NULL;
|
|
handle->monitor = mon;
|
|
}
|
|
|
|
handle->detectStaleMaster = config_get_bool(params, "detect_stale_master");
|
|
handle->script = config_copy_string(params, "script");
|
|
handle->events = config_get_enum(params, "events", mxs_monitor_event_enum_values);
|
|
|
|
if (!check_monitor_permissions(mon, "SHOW SLAVE STATUS"))
|
|
{
|
|
MXS_ERROR("Failed to start monitor. See earlier errors for more information.");
|
|
MXS_FREE(handle->script);
|
|
MXS_FREE(handle);
|
|
return NULL;
|
|
}
|
|
|
|
if (thread_start(&handle->thread, monitorMain, handle) == NULL)
|
|
{
|
|
MXS_ERROR("Failed to start monitor thread for monitor '%s'.", mon->name);
|
|
MXS_FREE(handle->script);
|
|
MXS_FREE(handle);
|
|
return NULL;
|
|
}
|
|
|
|
return handle;
|
|
}
|
|
|
|
/**
|
|
* Stop a running monitor
|
|
*
|
|
* @param arg Handle on thr running monior
|
|
*/
|
|
static void
|
|
stopMonitor(MXS_MONITOR *mon)
|
|
{
|
|
MM_MONITOR *handle = (MM_MONITOR *) mon->handle;
|
|
|
|
handle->shutdown = 1;
|
|
thread_wait(handle->thread);
|
|
}
|
|
|
|
/**
|
|
* Diagnostic interface
|
|
*
|
|
* @param dcb DCB to print diagnostics
|
|
* @param arg The monitor handle
|
|
*/
|
|
static void diagnostics(DCB *dcb, const MXS_MONITOR *mon)
|
|
{
|
|
const MM_MONITOR *handle = (const MM_MONITOR *) mon->handle;
|
|
|
|
dcb_printf(dcb, "Detect Stale Master:\t%s\n", (handle->detectStaleMaster == 1) ? "enabled" : "disabled");
|
|
}
|
|
|
|
/**
|
|
* Diagnostic interface
|
|
*
|
|
* @param arg The monitor handle
|
|
*/
|
|
static json_t* diagnostics_json(const MXS_MONITOR *mon)
|
|
{
|
|
const MM_MONITOR *handle = (const MM_MONITOR *)mon->handle;
|
|
|
|
json_t* rval = json_object();
|
|
json_object_set_new(rval, "detect_stale_master", json_boolean(handle->detectStaleMaster));
|
|
return rval;
|
|
}
|
|
|
|
/**
|
|
* Monitor an individual server
|
|
*
|
|
* @param handle The MySQL Monitor object
|
|
* @param database The database to probe
|
|
*/
|
|
static void
|
|
monitorDatabase(MXS_MONITOR* mon, MXS_MONITOR_SERVERS *database)
|
|
{
|
|
MYSQL_ROW row;
|
|
MYSQL_RES *result;
|
|
int isslave = 0;
|
|
int ismaster = 0;
|
|
unsigned long int server_version = 0;
|
|
char *server_string;
|
|
|
|
/* Don't probe servers in maintenance mode */
|
|
if (SERVER_IN_MAINT(database->server))
|
|
{
|
|
return;
|
|
}
|
|
|
|
/** Store previous status */
|
|
database->mon_prev_status = database->server->status;
|
|
mxs_connect_result_t rval = mon_ping_or_connect_to_db(mon, database);
|
|
|
|
if (rval != MONITOR_CONN_OK)
|
|
{
|
|
if (mysql_errno(database->con) == ER_ACCESS_DENIED_ERROR)
|
|
{
|
|
server_set_status_nolock(database->server, SERVER_AUTH_ERROR);
|
|
monitor_set_pending_status(database, SERVER_AUTH_ERROR);
|
|
}
|
|
server_clear_status_nolock(database->server, SERVER_RUNNING);
|
|
monitor_clear_pending_status(database, SERVER_RUNNING);
|
|
|
|
/* Also clear M/S state in both server and monitor server pending struct */
|
|
server_clear_status_nolock(database->server, SERVER_SLAVE);
|
|
server_clear_status_nolock(database->server, SERVER_MASTER);
|
|
monitor_clear_pending_status(database, SERVER_SLAVE);
|
|
monitor_clear_pending_status(database, SERVER_MASTER);
|
|
|
|
/* Clean addition status too */
|
|
server_clear_status_nolock(database->server, SERVER_STALE_STATUS);
|
|
monitor_clear_pending_status(database, SERVER_STALE_STATUS);
|
|
|
|
if (mon_status_changed(database) && mon_print_fail_status(database))
|
|
{
|
|
mon_log_connect_error(database, rval);
|
|
}
|
|
return;
|
|
}
|
|
else
|
|
{
|
|
server_clear_status_nolock(database->server, SERVER_AUTH_ERROR);
|
|
monitor_clear_pending_status(database, SERVER_AUTH_ERROR);
|
|
}
|
|
|
|
/* Store current status in both server and monitor server pending struct */
|
|
server_set_status_nolock(database->server, SERVER_RUNNING);
|
|
monitor_set_pending_status(database, SERVER_RUNNING);
|
|
|
|
/* get server version from current server */
|
|
server_version = mysql_get_server_version(database->con);
|
|
|
|
/* get server version string */
|
|
mxs_mysql_set_server_version(database->con, database->server);
|
|
server_string = database->server->version_string;
|
|
|
|
/* get server_id form current node */
|
|
if (mysql_query(database->con, "SELECT @@server_id") == 0
|
|
&& (result = mysql_store_result(database->con)) != NULL)
|
|
{
|
|
long server_id = -1;
|
|
|
|
if (mysql_field_count(database->con) != 1)
|
|
{
|
|
mysql_free_result(result);
|
|
MXS_ERROR("Unexpected result for 'SELECT @@server_id'. Expected 1 column."
|
|
" MySQL Version: %s", server_string);
|
|
return;
|
|
}
|
|
|
|
while ((row = mysql_fetch_row(result)))
|
|
{
|
|
server_id = strtol(row[0], NULL, 10);
|
|
if ((errno == ERANGE && (server_id == LONG_MAX
|
|
|| server_id == LONG_MIN)) || (errno != 0 && server_id == 0))
|
|
{
|
|
server_id = -1;
|
|
}
|
|
database->server->node_id = server_id;
|
|
}
|
|
mysql_free_result(result);
|
|
}
|
|
|
|
/* Check if the Slave_SQL_Running and Slave_IO_Running status is
|
|
* set to Yes
|
|
*/
|
|
|
|
/* Check first for MariaDB 10.x.x and get status for multimaster replication */
|
|
if (server_version >= 100000)
|
|
{
|
|
|
|
if (mysql_query(database->con, "SHOW ALL SLAVES STATUS") == 0
|
|
&& (result = mysql_store_result(database->con)) != NULL)
|
|
{
|
|
int i = 0;
|
|
long master_id = -1;
|
|
|
|
if (mysql_field_count(database->con) < 42)
|
|
{
|
|
mysql_free_result(result);
|
|
MXS_ERROR("\"SHOW ALL SLAVES STATUS\" returned less than the expected"
|
|
" amount of columns. Expected 42 columns MySQL Version: %s",
|
|
server_string);
|
|
return;
|
|
}
|
|
|
|
while ((row = mysql_fetch_row(result)))
|
|
{
|
|
/* get Slave_IO_Running and Slave_SQL_Running values*/
|
|
if (strncmp(row[12], "Yes", 3) == 0
|
|
&& strncmp(row[13], "Yes", 3) == 0)
|
|
{
|
|
isslave += 1;
|
|
}
|
|
|
|
/* If Slave_IO_Running = Yes, assign the master_id to current server: this allows building
|
|
* the replication tree, slaves ids will be added to master(s) and we will have at least the
|
|
* root master server.
|
|
* Please note, there could be no slaves at all if Slave_SQL_Running == 'No'
|
|
*/
|
|
if (strncmp(row[12], "Yes", 3) == 0)
|
|
{
|
|
/* get Master_Server_Id values */
|
|
master_id = atol(row[41]);
|
|
if (master_id == 0)
|
|
{
|
|
master_id = -1;
|
|
}
|
|
}
|
|
|
|
i++;
|
|
}
|
|
/* store master_id of current node */
|
|
memcpy(&database->server->master_id, &master_id, sizeof(long));
|
|
|
|
mysql_free_result(result);
|
|
|
|
/* If all configured slaves are running set this node as slave */
|
|
if (isslave > 0 && isslave == i)
|
|
{
|
|
isslave = 1;
|
|
}
|
|
else
|
|
{
|
|
isslave = 0;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
if (mysql_query(database->con, "SHOW SLAVE STATUS") == 0
|
|
&& (result = mysql_store_result(database->con)) != NULL)
|
|
{
|
|
long master_id = -1;
|
|
|
|
if (mysql_field_count(database->con) < 40)
|
|
{
|
|
mysql_free_result(result);
|
|
|
|
if (server_version < 5 * 10000 + 5 * 100)
|
|
{
|
|
if (database->log_version_err)
|
|
{
|
|
MXS_ERROR("\"SHOW SLAVE STATUS\" "
|
|
" for versions less than 5.5 does not have master_server_id, "
|
|
"replication tree cannot be resolved for server %s."
|
|
" MySQL Version: %s", database->server->unique_name, server_string);
|
|
database->log_version_err = false;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
MXS_ERROR("\"SHOW SLAVE STATUS\" "
|
|
"returned less than the expected amount of columns. "
|
|
"Expected 40 columns. MySQL Version: %s", server_string);
|
|
}
|
|
return;
|
|
}
|
|
|
|
while ((row = mysql_fetch_row(result)))
|
|
{
|
|
/* get Slave_IO_Running and Slave_SQL_Running values*/
|
|
if (strncmp(row[10], "Yes", 3) == 0
|
|
&& strncmp(row[11], "Yes", 3) == 0)
|
|
{
|
|
isslave = 1;
|
|
}
|
|
|
|
/* If Slave_IO_Running = Yes, assign the master_id to current server: this allows building
|
|
* the replication tree, slaves ids will be added to master(s) and we will have at least the
|
|
* root master server.
|
|
* Please note, there could be no slaves at all if Slave_SQL_Running == 'No'
|
|
*/
|
|
if (strncmp(row[10], "Yes", 3) == 0)
|
|
{
|
|
/* get Master_Server_Id values */
|
|
master_id = atol(row[39]);
|
|
if (master_id == 0)
|
|
{
|
|
master_id = -1;
|
|
}
|
|
}
|
|
}
|
|
/* store master_id of current node */
|
|
memcpy(&database->server->master_id, &master_id, sizeof(long));
|
|
|
|
mysql_free_result(result);
|
|
}
|
|
}
|
|
|
|
/* get variable 'read_only' set by an external component */
|
|
if (mysql_query(database->con, "SHOW GLOBAL VARIABLES LIKE 'read_only'") == 0
|
|
&& (result = mysql_store_result(database->con)) != NULL)
|
|
{
|
|
if (mysql_field_count(database->con) < 2)
|
|
{
|
|
mysql_free_result(result);
|
|
MXS_ERROR("Unexpected result for \"SHOW GLOBAL VARIABLES LIKE 'read_only'\". "
|
|
"Expected 2 columns. MySQL Version: %s", server_string);
|
|
return;
|
|
}
|
|
|
|
while ((row = mysql_fetch_row(result)))
|
|
{
|
|
if (strncasecmp(row[1], "OFF", 3) == 0)
|
|
{
|
|
ismaster = 1;
|
|
}
|
|
else
|
|
{
|
|
isslave = 1;
|
|
}
|
|
}
|
|
mysql_free_result(result);
|
|
}
|
|
|
|
/* Remove addition info */
|
|
monitor_clear_pending_status(database, SERVER_STALE_STATUS);
|
|
|
|
/* Set the Slave Role */
|
|
/* Set the Master role */
|
|
if (ismaster)
|
|
{
|
|
monitor_clear_pending_status(database, SERVER_SLAVE);
|
|
monitor_set_pending_status(database, SERVER_MASTER);
|
|
|
|
/* Set replication depth to 0 */
|
|
database->server->depth = 0;
|
|
}
|
|
else if (isslave)
|
|
{
|
|
monitor_set_pending_status(database, SERVER_SLAVE);
|
|
/* Avoid any possible stale Master state */
|
|
monitor_clear_pending_status(database, SERVER_MASTER);
|
|
|
|
/* Set replication depth to 1 */
|
|
database->server->depth = 1;
|
|
}
|
|
/* Avoid any possible Master/Slave stale state */
|
|
else
|
|
{
|
|
monitor_clear_pending_status(database, SERVER_SLAVE);
|
|
monitor_clear_pending_status(database, SERVER_MASTER);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* The entry point for the monitoring module thread
|
|
*
|
|
* @param arg The handle of the monitor
|
|
*/
|
|
static void
|
|
monitorMain(void *arg)
|
|
{
|
|
MM_MONITOR *handle = (MM_MONITOR *)arg;
|
|
MXS_MONITOR* mon = handle->monitor;
|
|
MXS_MONITOR_SERVERS *ptr;
|
|
int detect_stale_master = false;
|
|
MXS_MONITOR_SERVERS *root_master = NULL;
|
|
size_t nrounds = 0;
|
|
|
|
detect_stale_master = handle->detectStaleMaster;
|
|
|
|
if (mysql_thread_init())
|
|
{
|
|
MXS_ERROR("Fatal : mysql_thread_init failed in monitor module. Exiting.");
|
|
return;
|
|
}
|
|
|
|
handle->status = MXS_MONITOR_RUNNING;
|
|
while (1)
|
|
{
|
|
if (handle->shutdown)
|
|
{
|
|
handle->status = MXS_MONITOR_STOPPING;
|
|
mysql_thread_end();
|
|
handle->status = MXS_MONITOR_STOPPED;
|
|
return;
|
|
}
|
|
|
|
/** Wait base interval */
|
|
thread_millisleep(MXS_MON_BASE_INTERVAL_MS);
|
|
/**
|
|
* Calculate how far away the monitor interval is from its full
|
|
* cycle and if monitor interval time further than the base
|
|
* interval, then skip monitoring checks. Excluding the first
|
|
* round.
|
|
*/
|
|
if (nrounds != 0 &&
|
|
(((nrounds * MXS_MON_BASE_INTERVAL_MS) % mon->interval) >=
|
|
MXS_MON_BASE_INTERVAL_MS) && (!mon->server_pending_changes))
|
|
{
|
|
nrounds += 1;
|
|
continue;
|
|
}
|
|
nrounds += 1;
|
|
|
|
lock_monitor_servers(mon);
|
|
servers_status_pending_to_current(mon);
|
|
|
|
/* start from the first server in the list */
|
|
ptr = mon->databases;
|
|
|
|
while (ptr)
|
|
{
|
|
/* copy server status into monitor pending_status */
|
|
ptr->pending_status = ptr->server->status;
|
|
|
|
/* monitor current node */
|
|
monitorDatabase(mon, ptr);
|
|
|
|
if (mon_status_changed(ptr) ||
|
|
mon_print_fail_status(ptr))
|
|
{
|
|
MXS_DEBUG("Backend server [%s]:%d state : %s",
|
|
ptr->server->name,
|
|
ptr->server->port,
|
|
STRSRVSTATUS(ptr->server));
|
|
}
|
|
if (SERVER_IS_DOWN(ptr->server))
|
|
{
|
|
/** Increase this server'e error count */
|
|
ptr->mon_err_count += 1;
|
|
}
|
|
else
|
|
{
|
|
/** Reset this server's error count */
|
|
ptr->mon_err_count = 0;
|
|
}
|
|
|
|
ptr = ptr->next;
|
|
}
|
|
|
|
/* Get Master server pointer */
|
|
root_master = get_current_master(mon);
|
|
|
|
/* Update server status from monitor pending status on that server*/
|
|
|
|
ptr = mon->databases;
|
|
while (ptr)
|
|
{
|
|
if (!SERVER_IN_MAINT(ptr->server))
|
|
{
|
|
/* If "detect_stale_master" option is On, let's use the previus master */
|
|
if (detect_stale_master && root_master &&
|
|
(!strcmp(ptr->server->name, root_master->server->name) &&
|
|
ptr->server->port == root_master->server->port) && (ptr->server->status & SERVER_MASTER) &&
|
|
!(ptr->pending_status & SERVER_MASTER))
|
|
{
|
|
/* in this case server->status will not be updated from pending_status */
|
|
MXS_NOTICE("root server [%s:%i] is no longer Master, let's "
|
|
"use it again even if it could be a stale master, you have "
|
|
"been warned!", ptr->server->name, ptr->server->port);
|
|
/* Set the STALE bit for this server in server struct */
|
|
server_set_status_nolock(ptr->server, SERVER_STALE_STATUS);
|
|
}
|
|
else
|
|
{
|
|
ptr->server->status = ptr->pending_status;
|
|
}
|
|
}
|
|
ptr = ptr->next;
|
|
}
|
|
|
|
/**
|
|
* After updating the status of all servers, check if monitor events
|
|
* need to be launched.
|
|
*/
|
|
mon_process_state_changes(mon, handle->script, handle->events);
|
|
|
|
mon_hangup_failed_servers(mon);
|
|
servers_status_current_to_pending(mon);
|
|
release_monitor_servers(mon);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Enable/Disable the MySQL Replication Stale Master dectection, allowing a previouvsly detected master to still act as a Master.
|
|
* This option must be enabled in order to keep the Master when the replication is stopped or removed from slaves.
|
|
* If the replication is still stopped when MaxSclale is restarted no Master will be available.
|
|
*
|
|
* @param arg The handle allocated by startMonitor
|
|
* @param enable To enable it 1, disable it with 0
|
|
*/
|
|
/* Not used
|
|
static void
|
|
detectStaleMaster(void *arg, int enable)
|
|
{
|
|
MONITOR* mon = (MONITOR*) arg;
|
|
MM_MONITOR *handle = (MM_MONITOR *) mon->handle;
|
|
memcpy(&handle->detectStaleMaster, &enable, sizeof(int));
|
|
}
|
|
*/
|
|
|
|
/*******
|
|
* This function returns the master server
|
|
* from a set of MySQL Multi Master monitored servers
|
|
* and returns the root server (that has SERVER_MASTER bit)
|
|
* The server is returned even for servers in 'maintenance' mode.
|
|
*
|
|
* @param handle The monitor handle
|
|
* @return The server at root level with SERVER_MASTER bit
|
|
*/
|
|
|
|
static MXS_MONITOR_SERVERS *get_current_master(MXS_MONITOR *mon)
|
|
{
|
|
MM_MONITOR* handle = mon->handle;
|
|
MXS_MONITOR_SERVERS *ptr;
|
|
|
|
ptr = mon->databases;
|
|
|
|
while (ptr)
|
|
{
|
|
/* The server could be in SERVER_IN_MAINT
|
|
* that means SERVER_IS_RUNNING returns 0
|
|
* Let's check only for SERVER_IS_DOWN: server is not running
|
|
*/
|
|
if (SERVER_IS_DOWN(ptr->server))
|
|
{
|
|
ptr = ptr->next;
|
|
continue;
|
|
}
|
|
|
|
if (ptr->server->depth == 0)
|
|
{
|
|
handle->master = ptr;
|
|
}
|
|
|
|
ptr = ptr->next;
|
|
}
|
|
|
|
|
|
/*
|
|
* Return the root master
|
|
*/
|
|
|
|
if (handle->master != NULL)
|
|
{
|
|
/* If the root master is in MAINT, return NULL */
|
|
if (SERVER_IN_MAINT(handle->master->server))
|
|
{
|
|
return NULL;
|
|
}
|
|
else
|
|
{
|
|
return handle->master;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
return NULL;
|
|
}
|
|
}
|