Openresty处理流程

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记录下openresty处理流程，方便后续学习使用

init阶段
- init_by_lua：运行在Nginx loading-config 阶段，注册Nginx Lua全局变量，和一些预加载模块。是Nginx master进程在加载Nginx配置时执行
- init_worker_by_lua：在Nginx starting-worker阶段，即每个nginx worker启动时会调用，通常用来hook worker进程，并创建worker进行的计时器，用来健康检查，或者设置熔断记时窗口等等
rewrite/access阶段
- access_by_lua：在access tail阶段，用来对每次请求做访问控制，权限校验等等，能拿到很多相关变量。例如：请求体中的值，header中的值，可以将值添加到ngx.ctx, 在其他模块进行相应的控制
- set_by_lua：流程分支处理判断变量初始化
- rewrite_by_lua：转发、重定向、缓存等功能(例如特定请求代理到外网)
content阶段
- content_by_lua：内容生成，对于每个api请求进行处理，注意不能与proxy_pass放在同一个location下
- balancer_by_lua：可以实现不同的负载均衡策略，并调用set_current_peer函数设置当前query调用的backend
- header_filter_by_lua：在output-header-filter阶段，通常用来重新响应头部，设置cookie等，也可以用来作熔断触发标记
- body_filter_by_lua：应答 BODY 过滤处理(例如完成应答内容统一成大写)
log阶段
- log_by_lua：记录日志，记录一下整个请求的耗时，状态码等

一个样例

location /mixed {
    set_by_lua_block $a {
        ngx.log(ngx.ERR, "set_by_lua*")
    }
    rewrite_by_lua_block {
        ngx.log(ngx.ERR, "rewrite_by_lua*")
    }
    access_by_lua_block {
        ngx.log(ngx.ERR, "access_by_lua*")
    }
    content_by_lua_block {
        ngx.log(ngx.ERR, "content_by_lua*")
    }
    header_filter_by_lua_block {
        ngx.log(ngx.ERR, "header_filter_by_lua*")
    }
    body_filter_by_lua_block {
        ngx.log(ngx.ERR, "body_filter_by_lua*")
    }
    log_by_lua_block {
        ngx.log(ngx.ERR, "log_by_lua*")
    }
}

在error.log中查看调试输出

2021/03/26 02:12:58 [error] 5561#0: *1 [lua] set_by_lua:2: set_by_lua*, client: 192.168.44.145, server: openresty.xadocker.cn, request: "GET /mixed HTTP/1.1", host: "openresty.xadocker.cn"
2021/03/26 02:12:58 [error] 5561#0: *1 [lua] rewrite_by_lua(openresty.xadocker.cn.conf:254):2: rewrite_by_lua*, client: 192.168.44.145, server: openresty.xadocker.cn, request: "GET /mixed HTTP/1.1", host: "openresty.xadocker.cn"
2021/03/26 02:12:58 [error] 5561#0: *1 [lua] access_by_lua(openresty.xadocker.cn.conf:257):2: access_by_lua*, client: 192.168.44.145, server: openresty.xadocker.cn, request: "GET /mixed HTTP/1.1", host: "openresty.xadocker.cn"
2021/03/26 02:12:58 [error] 5561#0: *1 [lua] content_by_lua(openresty.xadocker.cn.conf:260):2: content_by_lua*, client: 192.168.44.145, server: openresty.xadocker.cn, request: "GET /mixed HTTP/1.1", host: "openresty.xadocker.cn"
2021/03/26 02:12:58 [error] 5561#0: *1 [lua] header_filter_by_lua:2: header_filter_by_lua*, client: 192.168.44.145, server: openresty.xadocker.cn, request: "GET /mixed HTTP/1.1", host: "openresty.xadocker.cn"
2021/03/26 02:12:58 [error] 5561#0: *1 [lua] body_filter_by_lua:2: body_filter_by_lua*, client: 192.168.44.145, server: openresty.xadocker.cn, request: "GET /mixed HTTP/1.1", host: "openresty.xadocker.cn"
2021/03/26 02:12:58 [error] 5561#0: *1 [lua] log_by_lua(openresty.xadocker.cn.conf:269):2: log_by_lua* while logging request, client: 192.168.44.145, server: openresty.xadocker.cn, request: "GET /mixed HTTP/1.1", host: "openresty.xadocker.cn"