【Gearman学习笔记】分布式处理入门

1.首先，确保你已经安装了gearmand环境并且语言绑定（language binding）已经生效。

2.涉及到的各个部分：

Server

The server, gearmand, will coordinate clients and workers ensuring that calls from the clients are delivered to workers and that results from workers are sent back to the client.

gearmand作为我们的服务端，使client和worker协同工作，确保从client端发过来的请求能够传送到worker，同时使经过worker处理过的请求结果能够返回给client。

Client

A process which has a blob of data to process, a known function which can process it, and a desire to get the processed results back. In our case, the client wants a string reversed.

Client就是一个有很多待处理数据的进程，它能够被其他程序处理并得到处理后的返回结果。在我们的例子中，client端的需求是使一个字符串翻转。

Worker

A process which connected to the server and offers to process function calls. In this example, the client can reverse strings.

Worker是一个连接到server的进程，server端接收到client的请求后，把任务分派给worker，worker对请求作出处理。在我们的例子中，worker要做的任务是翻转一份字符串。

3.client.php（本文使用PHP作为客户端）：

<?php

// Create our client object
$client = new GearmanClient();

// Add a server
$client->addServer(); // by default host/port will be "localhost" & 4730

echo "Sending job\n";

// Send reverse job
$result = $client->doNormal("reverse", "Hello!");
if ($result) {
  echo "Success: $result\n";
}

4.worker.py（本文使用Python作为worker）：

import gearman

gm_worker = gearman.GearmanWorker(['localhost:4730'])

def task_listener_reverse(gearman_worker, gearman_job):
    print 'Reversing string: ' + gearman_job.data
    return gearman_job.data[::-1]

# gm_worker.set_client_id is optional
gm_worker.set_client_id('python-worker')
gm_worker.register_task('reverse', task_listener_reverse)

# Enter our work loop and call gm_worker.after_poll() after each time we timeout/see socket activity
gm_worker.work()

5.测试：

测试环境配置：

 Linux3.5.7-gentoo #1  x86_64 Intel(R) Xeon(R) CPU E5645 @ 2.40GHz GenuineIntel GNU/Linux

因为我在gentoo server下面，没法开两个terminal，所以，要先把worker.py作为后台进程运行：

然后，用php CLI运行client.php：

可以看到，在gearman的协调下，worker完成一次client的请求。

6.英文出处：http://gearman.org/examples/reverse/

7.【更新】

上面的例子讲的是同步机制，这还体现不出gearman的强大，下面是doBackground()的异步机制：

http://gearman.org/examples/send-emails/