用HTTP模式调用gearman任务处理

原文：

This protocol plugin allows you to map HTTP requests to Gearman jobs. It only provides client job submission currently, but it may be extended to support other request types in the future. The plugin can handle both GET and POST data, the latter being used to send a workload to the job server. The URL being requested is translated into the function being called.

For example, the request:

POST /reverse HTTP/1.1
Content-Length: 12

Hello world!

Is translated into a job submission request for the function “reverse” and workload “Hello world!”. This will respond with:

HTTP/1.0 200 OK
X-Gearman-Job-Handle: H:lap:4
Content-Length: 12
Server: Gearman/0.8

!dlrow olleH

The following headers can be passed to change the behavior of the job:

* X-Gearman-Unique: <unique key>
* X-Gearman-Background: true
* X-Gearman-Priority: <high|low>

For example, to run a low priority background job, the following request can be sent:

POST /reverse HTTP/1.1
Content-Length: 12
X-Gearman-Background: true
X-Gearman-Priority: low

Hello world!

The response for this request will not have any data associated with it since it was a background job:

HTTP/1.0 200 OK
X-Gearman-Job-Handle: H:lap:6
Content-Length: 0
Server: Gearman/0.8

The HTTP protocol should be considered experimental.

应用场景：

开启gearman http监听功能，让前端以web api方式调用gearman job

起用方式：

在gearmand的起动参数中加上：

/usr/local/gearman/sbin/gearmand        \
-l /usr/local/gearman/log/trace.log     \
--verbose INFO -p 4730 -u root -d -t 4  \
--http-port=8080                        \
-r http

--http-port=8080 指定监听端口号

-r http 起用http协议模块

调用方式：

目前http协议只支持任务提交类接口，其它类型的暂不支持。

按官方文档上说，http支持GET和POS两种方式调用，但是GET方式我还没弄清楚怎样携带数据，POST方式实验过是可以的

http://172.16.18.116:8080/reverse

reverse就为函数名，假如POST的数据内容为：“Hello world!”，返回结果为：“!dlrow olleH”

在http的header头中可以设置一些任务参数：

* X-Gearman-Unique: <unique key>
* X-Gearman-Background: true
* X-Gearman-Priority: <high|low>

这种使用方式，实际上gearmand监听着两个端，原来的4730端还是可以接收正常的gearman协议客户端的请求，另外的8080端口则监听着http协议的请求，两种方式共同工作，http服务前端如移动端调用，gearman服务内部的其它模块的调用。

必须要注意，如果是内部调用就无需用http方式了，一般是外部调用才会用http方式，但是这种方式很不安全，尤其是如果暴露在公网地址，很容易被攻击，而且gearman的http服务远没有专业的web server健壮，我昨天开始试用，结果就被攻击了，一下子内存耗尽gearman崩溃，OS都不动了。