使用php作為后臺運行程序（例如短信群發(fā)）梧躺，在cli模式下執(zhí)行php，php需要連接mysql循環(huán)執(zhí)行數(shù)據(jù)庫處理傲绣。
當(dāng)mysql連接閃斷時掠哥，之后循環(huán)的執(zhí)行將會失敗。
我們需要設(shè)計一個方法秃诵，當(dāng)mysql閃斷時续搀，可以自動重新連接，使后面的程序可以正常執(zhí)行下去菠净。
1.創(chuàng)建測試數(shù)據(jù)表
CREATE TABLE `user` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
2.插入測試數(shù)據(jù)
insert into user(name) values('fdipzone'),('xfdipzone'),('terry');
mysql> select * from user;
+----+-----------+
| id | name |
+----+-----------+
| 1 | fdipzone |
| 2 | xfdipzone |
| 3 | terry |
+----+-----------+
3.后臺運行的php文件
db.php
<?php
// 數(shù)據(jù)庫操作類
class DB{
// 保存數(shù)據(jù)庫連接
private static $_instance = null;
// 連接數(shù)據(jù)庫
public static function get_conn($config){if(isset(self::$_instance) && !empty(self::$_instance)){
return self::$_instance;
}
$dbhost = $config['host'];
$dbname = $config['dbname'];
$dbuser = $config['user'];
$dbpasswd = $config['password'];
$pconnect = $config['pconnect'];
$charset = $config['charset'];
$dsn = "mysql:host=$dbhost;dbname=$dbname;";
try {
$h_param = array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
);
if ($charset != '') {
$h_param[PDO::MYSQL_ATTR_INIT_COMMAND] = 'SET NAMES ' . $charset; //設(shè)置默認編碼
}
if ($pconnect) {
$h_param[PDO::ATTR_PERSISTENT] = true;
}
$conn = new PDO($dsn, $dbuser, $dbpasswd, $h_param);
} catch (PDOException $e) {
throw new ErrorException('Unable to connect to db server. Error:' . $e->getMessage(), 31);
}
self::$_instance = $conn;
return $conn;
}
// 執(zhí)行查詢
public static function query($dbconn, $sqlstr, $condparam){
$sth = $dbconn->prepare($sqlstr);
try{
$sth->execute($condparam);
} catch (PDOException $e) {
echo $e->getMessage().PHP_EOL;
}
$result = $sth->fetchAll(PDO::FETCH_ASSOC);
return $result;
}
}
?>
test.php
<?php
require 'db.php';
// 數(shù)據(jù)庫設(shè)定
$config = array(
'host' => 'localhost',
'dbname' => 'user',
'user' => 'root',
'password' => '',
'pconnect' => 0,
'charset' => ''
);
// 循環(huán)執(zhí)行
while(true){
// 創(chuàng)建數(shù)據(jù)連接
$dbconn = DB::get_conn($config);
// 執(zhí)行查詢
$sqlstr = 'select * from user where id=?';
$condparam = array(mt_rand(1,3));
$data = DB::query($dbconn, $sqlstr, $condparam);
print_r($data);
// 延時10秒
echo 'sleep 10'.PHP_EOL.PHP_EOL;
sleep(10);
}
?>
4.執(zhí)行步驟
在php cli模式下執(zhí)行test.php禁舷，然后馬上執(zhí)行mysql.server stop 與 mysql.server start 模擬閃斷
mysql.server stop
Shutting down MySQL
.. SUCCESS!
mysql.server start
Starting MySQL
SUCCESS!
可以看到，閃斷后不能重新連接數(shù)據(jù)庫毅往，后面的程序不能執(zhí)行下去牵咙。
Array
(
[0] => Array
(
[id] => 3
[name] => terry
)
)
sleep 10
SQLSTATE[HY000]: General error: 2006 MySQL server has gone away
Array
(
)
sleep 10
SQLSTATE[HY000]: General error: 2006 MySQL server has gone away
Array
(
)
sleep 10
...
5.增加重連機制
if(isset(self::$_instance) && !empty(self::$_instance)){
return self::$_instance;
}
閃斷后，因為 self::$_instance 的值存在攀唯，因此調(diào)用get_conn并不會重新連接洁桌，而是使用保存的連接進行處理。
這樣實際上是當(dāng)連接存在時革答，不需要再次創(chuàng)建mysql連接战坤，減少mysql連接數(shù)。
所以需要在閃斷后残拐，清空self::$_instance的值，使下次重新獲取連接碟嘴，而不使用已經(jīng)創(chuàng)建但失效的數(shù)據(jù)庫連接溪食。
改進方法如下：
增加reset_connect方法，當(dāng)出現(xiàn)錯誤時調(diào)用娜扇。如果判斷錯誤是MySQL server has gone away則清空已經(jīng)存在的數(shù)據(jù)庫連接错沃，清空后下次則會重新連接mysql。
修改后的php文件如下:
db.php
<?php
// 數(shù)據(jù)庫操作類
class DB{
// 保存數(shù)據(jù)庫連接
private static $_instance = null;
// 連接數(shù)據(jù)庫
public static function get_conn($config){if(isset(self::$_instance) && !empty(self::$_instance)){
return self::$_instance;
}
$dbhost = $config['host'];
$dbname = $config['dbname'];
$dbuser = $config['user'];
$dbpasswd = $config['password'];
$pconnect = $config['pconnect'];
$charset = $config['charset'];
$dsn = "mysql:host=$dbhost;dbname=$dbname;";
try {
$h_param = array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
);
if ($charset != '') {
$h_param[PDO::MYSQL_ATTR_INIT_COMMAND] = 'SET NAMES ' . $charset; //設(shè)置默認編碼
}
if ($pconnect) {
$h_param[PDO::ATTR_PERSISTENT] = true;
}
$conn = new PDO($dsn, $dbuser, $dbpasswd, $h_param);
} catch (PDOException $e) {
throw new ErrorException('Unable to connect to db server. Error:' . $e->getMessage(), 31);
}
self::$_instance = $conn;
return $conn;
}
// 執(zhí)行查詢
public static function query($dbconn, $sqlstr, $condparam){
$sth = $dbconn->prepare($sqlstr);
try{
$sth->execute($condparam);
} catch (PDOException $e) {
echo $e->getMessage().PHP_EOL;
self::reset_connect($e->getMessage()); // 出錯時調(diào)用重置連接
}
$result = $sth->fetchAll(PDO::FETCH_ASSOC);
return $result;
}
// 重置連接
public static function reset_connect($err_msg){
if(strpos($err_msg, 'MySQL server has gone away')!==false){
self::$_instance = null;
}
}
}
?>
6.再次進行閃斷執(zhí)行
可以看到改進后的效果雀瓢，閃斷后枢析，當(dāng)前執(zhí)行的會失敗，但之后的可以重新創(chuàng)建新連接繼續(xù)執(zhí)行下去刃麸。
Array
(
[0] => Array
(
[id] => 2
[name] => xfdipzone
)
)
sleep 10
SQLSTATE[HY000]: General error: 2006 MySQL server has gone away
Array
(
)
sleep 10
Array
(
[0] => Array
(
[id] => 1
[name] => fdipzone
)
)
sleep 10
...
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