EMQX中如何使用hooks功能

【EMQX开始hook功能】
The EMQ broker implements a simple but powerful hooks mechanism to help users develop plugin.
The broker would run the hooks when a client is connected/disconnected, a topic is subscribed/unsubscribed or a MQTT message is published/delivered/acked

EMQX实现了简单并强大的hooks机制，帮助用户开发插件。
Broker在以下情况下运行hook：客户端建立连接、客户端断开连接、订阅主题、取消订阅主题、消息发布、消息分发、消息应答

1> EMQX提供两种hook，luahook和webhook
2> hook属于插件功能，开启hook有以下方式：

A> 通过# ./emqx_ctl plugins子命令进行配置
   =># ./emqx_ctl plugins load emqx_web_hook
   =># ./emqx_ctl plugins unload emqx_web_hook

B> 通过emqx webconsole在界面进行配置

3> webhook默认支持以下action
//////////begin///////////
web.hook.rule.client.connected.1     = {"action": "on_client_connected"}
web.hook.rule.client.disconnected.1  = {"action": "on_client_disconnected"}
web.hook.rule.client.subscribe.1     = {"action": "on_client_subscribe"}
web.hook.rule.client.unsubscribe.1   = {"action": "on_client_unsubscribe"}
web.hook.rule.session.created.1      = {"action": "on_session_created"}
web.hook.rule.session.subscribed.1   = {"action": "on_session_subscribed"}
web.hook.rule.session.unsubscribed.1 = {"action": "on_session_unsubscribed"}
web.hook.rule.session.terminated.1   = {"action": "on_session_terminated"}
web.hook.rule.message.publish.1      = {"action": "on_message_publish"}
web.hook.rule.message.deliver.1    = {"action": "on_message_deliver"}
web.hook.rule.message.acked.1        = {"action": "on_message_acked"}
//////////end////////////
注意：实际使用时，可针对需要的hook action进行配置，仅保留需要的ation即可，
比如：需要检测客户端是否断开的行为，可以只保留【on_client_disconnected】这个action。

4> webhook默认发起请求的方式如下：
0> uri=>可根据实际使用场景进行配置
1> method=POST
2> content-type=application/json
3> body data如下：
//////////////begin////////
{"action":"session_terminated","client_id":"ac110a0f98e25d9d8b75","reason":"normal"}
//////////////end//////////
注意：可通过client_id来关联到实际业务场景中；

参考：https://github.com/emqx/emqx-web-hook