What are the steps to use redis long connection in php

This time I will bring you the steps for using redis long connection in php, and what are the precautions for using redis long connection in php. The following is a practical case, let's take a look.

php-redis project address on github: https://github.com/phpredis/phpredis

pconnect function declaration

Time_out indicates how many seconds the client will be idle before disconnecting. The function connection returns true if successful and false if failed:

pconnect(host, port, time_out, persistent_id, retry_interval)
    host: string. can be a host, or the path to a unix domain socket
    port: int, optional
    timeout: float, value in seconds (optional, default is 0 meaning unlimited)
    persistent_id: string. identity for the requested persistent connection
    retry_interval: int, value in milliseconds (optional)

The following example details the reuse of pconnect connections.

$redis->pconnect('127.0.0.1', 6379);
$redis->pconnect('127.0.0.1'); // 默认端口6379,跟上面的例子使用相同的连接。
$redis->pconnect('127.0.0.1', 6379, 2.5); // 设置了2.5秒的过期时间。将是不同于上面的新连接
$redis->pconnect('127.0.0.1', 6379, 2.5, 'x'); //设置了持久连接的id，将是不同于上面的新连接
$redis->pconnect('/tmp/redis.sock'); // unix domain socket - would be another connection than the four before.

Introduction to the use of pconnect

A brief description of the pconnect method

Use this method to create a connection , the connection will not be closed after calling the close method, the connection will only be closed after the process ends.

[To be verified] If you are using a long connection, the timeout configuration item in the Redis configuration file needs to be set to 0, otherwise the connection in the connection pool will expire due to timeout.

Explain pconnect for PHP-FPM

Long connections will only end after the PHP-FPM process ends, the

life cycle of the connection is the life cycle of the PHP-FPM process. Compared with shorter connections, a redis connection will be generated during each PHP-FPM call. The representation on the server is excessive time_out connection status.
On the contrary, long connections, all CGIs called by PHP-FPM will only share one long connection, so only a fixed number of time_out will be generated.

Close long connections

You can call the close and unset methods, but they are very different:

-

close The function is only to prevent the current PHP process from making redis requests, but it cannot actually close the long redis connection. The connection will still be reused in subsequent requests until the FPM process life cycle ends. So close does not destroy the redis object, it just disconnects it.

-

unset The variable will be destroyed. It should also be noted that you do not need to close if you use pconnect. If the current script execution time is very long, it will always occupy a connection.

How to determine whether the current Redis is in the connected state

The equivalent problem is to determine whether the current instance is valid in

single case mode.

It is customary to call echo to determine whether the string itself is returned normally, or call ping to see whether the return value is PONG.

But you need to be particularly careful. After redis disconnects, when calling echo and ping (returning 'POMG'), an exception

will be thrown. So it needs to be handled through the exception catching mechanism.

Code analysis of pconnect connection reuse issues

Situation 1: Non-singleton mode.

Explanation: Instance a and instance b share a connection, and instance b modifies the connection of instance a:

So the following example causes the final value of instance $a to become 2 , requires special attention.

$a = pconnect(host, port, time_out);
select(3);
$a -> setex(id, 3);
echo $a -> get(id);
//之后执行下面的连接
$b = pconnect(host, port, time_out);
select(2);
$b->set(id,2)
echo $a->get(id);  //这个id操作的db变成了2，不再是之前的3了。因为这两个连接共用了一个连接通道。

Scenario 2: Singleton mode.

Modify the above code so that both a and b are generated through getInstance. The prerequisite for generation is to determine whether the current instance exists. The confusion point of the singleton mode is:

$a generates an instance. At this time, $b is generated. $b uses the instance of $a, and then modifies the connection of $a. Then calling $a must be The modified instance of $b called. Same as situation two.

The code for singleton mode is as follows:

public static function getInstance($db = 0)
{
  if (!isset(self::$_instance)) {
    self::$_instance = new Redis();
  }
  self::_connect();
  self::$_instance->select($db);
  return self::$_instance;
}

Both cases illustrate the problem of connection reuse. How to fix this bug? Two points:

1. Generate a single instance for each db.

2. Avoid connection reuse issues.

So the code can be adjusted to return a singleton array:

public static function getInstance($db = 0)
{
  try{
    if (isset(self::$_instance[$db]) && self::$_instance[$db]->Ping() == 'Pong') {
      return self::$_instance[$db];
    }
  } catch (Exception $e) {
  }
  self::$_instance[$db] = new Redis();
  self::_connect($db);
  return self::$_instance[$db];
}

Things to note

Avoid using the Use redis objects in class member variables.

In the singleton mode of redis, the expiration time of time_out is declared. If the occasion for redis processing is a task, and the interval between task calls to redis is relatively long. When the interval is greater than time_out, redis will disconnect, and all operations on redis will fail. The solution is to avoid this calling method and execute it by dynamically declaring the redis class at the place of call. This problem does not distinguish between long connections and short links, and it is an error in the calling method.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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