用HTTP方式调用gearman任务处理

本来以为是个挺美好的东西，结果。。。

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webserver健壮。

攻击方式很简单：telnet host 8080，连接成功后，随便输入点内容，如：aaa，gearman日志就不停的出现如下错误信息：

bad request line:aaa

简直就是死循环，gearmand就顶不住了，系统内存也一会就被耗尽，说明http这块实现的有BUG。

不过可以通过修改源码来修复这个BUG：

You can open file libgearman-server/plugins/protocol/http/protocol.cc , find 'bad request line:' and 'bad method:', then chang 'GEARMAND_SUCCESS' to 'GEARMAND_INVALID_PACKET' after them. This way is quick for this bug.

也可以下载下面的补丁，对源patch：

https://bugs.launchpad.net/gearmand/+bug/1348865/+attachment/4182968/+files/gearmand-1.1.12.patch

gearmand-1.1.12源码安装目录下执行：patch -p0 < ../gearmand-1.1.12.patch

该补丁解决了上面的错误，同时也增加了对get方法的支持

bug信息参见：https://bugs.launchpad.net/gearmand/+bug/1348865

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。