Last-Modified: 2019 年 5 月 10 日 16:06:36

前言

小型 web 服务, session 数据基本是保存在本地 (更多是本地磁盘文件), 但是当部署多台服务, 且需要共享 session, 确保每个服务都能共享到同一份 session 数据.

redis 数据存储在内存中, 性能好, 配合持久化可确保数据完整.

设计方案

1. 通过 php 自身 session 配置实现

# 使用 redis 作为存储方案
session.save_handler = redis
session.save_path = "tcp://127.0.0.1:6379"
# 若设置了连接密码, 则使用如下
session.save_path = "tcp://127.0.0.1:6379?auth= 密码"

测试代码

<?php
ini_set("session.save_handler", "redis");
ini_set("session.save_path", "tcp://127.0.0.1:6379");

session_start();
echo "<pre>";
$_SESSION['usertest'.rand(1,5)]=1;
var_dump($_SESSION);

echo "</pre>";

输出 ↓

array(2) {["usertest1"]=>
  int(88)
  ["usertest3"]=>
  int(1)
}
usertest1|i:1;usertest3|i:1;

评价

• 优点: 实现简单, 无需修改 php 代码
• 缺点: 配置不支持多样化, 只能应用于简单场景

2. 设置用户自定义会话存储函数

通过 session_set_save_handler() 函数设置用户自定义会话函数.

session_set_save_handler (callable $open , callable $close , callable $read , callable $write , callable $destroy , callable $gc [, callable $create_sid [, callable $validate_sid [, callable $update_timestamp]]] ) : bool
    
# >= php5.4
session_set_save_handler (object $sessionhandler [, bool $register_shutdown = TRUE] ) : bool

在配置完会话存储函数后, 再执行 session_start() 即可.

具体代码略, 以下提供一份 Memcached 的 (来自 Symfony 框架代码):

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpFoundation\Session\Storage\Handler;

/**
 * MemcacheSessionHandler.
 *
 * @author Drak <drak@zikula.org>
 */
class MemcacheSessionHandler implements \SessionHandlerInterface
{
    /**
     * @var \Memcache Memcache driver.
     */
    private $memcache;

    /**
     * @var int Time to live in seconds
     */
    private $ttl;

    /**
     * @var string Key prefix for shared environments.
     */
    private $prefix;

    /**
     * Constructor.
     *
     * List of available options:
     *  * prefix: The prefix to use for the memcache keys in order to avoid collision
     *  * expiretime: The time to live in seconds
     *
     * @param \Memcache $memcache A \Memcache instance
     * @param array     $options  An associative array of Memcache options
     *
     * @throws \InvalidArgumentException When unsupported options are passed
     */
    public function __construct(\Memcache $memcache, array $options = array())
    {if ($diff = array_diff(array_keys($options), array('prefix', 'expiretime'))) {
            throw new \InvalidArgumentException(sprintf('The following options are not supported"%s"', implode(', ', $diff)
            ));
        }

        $this->memcache = $memcache;
        $this->ttl = isset($options['expiretime']) ? (int) $options['expiretime'] : 86400;
        $this->prefix = isset($options['prefix']) ? $options['prefix'] : 'sf2s';
    }

    /**
     * {@inheritdoc}
     */
    public function open($savePath, $sessionName)
    {return true;}

    /**
     * {@inheritdoc}
     */
    public function close()
    {return $this->memcache->close();
    }

    /**
     * {@inheritdoc}
     */
    public function read($sessionId)
    {return $this->memcache->get($this->prefix.$sessionId) ?: '';
    }

    /**
     * {@inheritdoc}
     */
    public function write($sessionId, $data)
    {return $this->memcache->set($this->prefix.$sessionId, $data, 0, time() + $this->ttl);
    }

    /**
     * {@inheritdoc}
     */
    public function destroy($sessionId)
    {return $this->memcache->delete($this->prefix.$sessionId);
    }

    /**
     * {@inheritdoc}
     */
    public function gc($maxlifetime)
    {
        // not required here because memcache will auto expire the records anyhow.
        return true;
    }

    /**
     * Return a Memcache instance
     *
     * @return \Memcache
     */
    protected function getMemcache()
    {return $this->memcache;}
}