Web开发平台OpenResty（四）: 项目开发中常用的操作

说明

这里记录一下基于OpenResty的项目开发时，经常用到的操作，譬如读取nginx内置变量、打印调试日志等

以下操作的很大一部分都是在使用lua-nginx-module的lua api

打印日志

ngx.log用来打印各个级别的日志。

ngx.STDERR
ngx.EMERG
ngx.ALERT
ngx.CRIT
ngx.ERR
ngx.WARN
ngx.NOTICE
ngx.INFO
ngx.DEBUG

显示的日志级别用nginx的error_log指令设置，可以设置的级别有：

debug, info, notice, warn, error, crit, alert,  emerg

使用方法：

#study-OpenResty/example/06-nginx-lua-module-log
worker_processes  1;              #nginx worker 数量
error_log logs/error.log debug;   #指定错误日志文件路径
events {
  worker_connections 1024;
}

http {
     server {
         listen 6699;
         location / {
             content_by_lua_block {
                ngx.log(ngx.DEBUG,"this is a DEBUG log");
                ngx.log(ngx.INFO,"this is a INFO log");
                ngx.log(ngx.NOTICE,"this is a NOTICE log");
                ngx.log(ngx.WARN,"this is a WARN log");
                ngx.log(ngx.ERR,"this is a ERR log");
                ngx.log(ngx.CRIT,"this is a CRIT log");
                ngx.log(ngx.ALERT,"this is a ALERT log");
                ngx.log(ngx.EMERG,"this is a EMERG log");
                ngx.log(ngx.STDERR,"this is a STDERR log");
             }
         }
     }
 }

发起访问：

$ curl 127.0.0.1:6699

在logs/error.log中可以看到下面的日志：

2018/11/09 18:52:22 [notice] 60535#2188182: using the "kqueue" event method
2018/11/09 18:52:22 [notice] 60535#2188182: start worker processes
2018/11/09 18:52:22 [notice] 60535#2188182: start worker process 60942
2018/11/09 18:52:22 [notice] 60535#2188182: signal 23 (SIGIO) received
2018/11/09 18:52:22 [notice] 60535#2188182: signal 23 (SIGIO) received
2018/11/09 18:52:22 [notice] 60535#2188182: signal 20 (SIGCHLD) received from 60763
2018/11/09 18:52:22 [notice] 60535#2188182: worker process 60763 exited with code 0
2018/11/09 18:52:22 [notice] 60535#2188182: signal 23 (SIGIO) received
2018/11/09 18:52:22 [notice] 60535#2188182: signal 23 (SIGIO) received from 60942
2018/11/09 18:52:23 [debug] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):2: this is a DEBUG log
2018/11/09 18:52:23 [info] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):3: this is a INFO log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [notice] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):4: this is a NOTICE log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [warn] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):5: this is a WARN log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [error] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):6: this is a ERR log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [crit] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):7: this is a CRIT log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [alert] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):8: this is a ALERT log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [emerg] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):9: this is a EMERG log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [] 60942#2206384: *4 [lua] content_by_lua(nginx.conf:22):10: this is a STDERR log, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:6699"
2018/11/09 18:52:23 [info] 60942#2206384: *4 kevent() reported that client 127.0.0.1 closed keepalive connection

读取nginx的内置变量

Nginx: Alphabetical index of variables中列出了nginx内置的变量，这些变量可以在nginx的配置文件中直接使用。如果要在OpenResty中使用，用lua-nginx-module的ngx.var.VARIABLE获取。

例如要读取变量$request_uri，可以用下面的方式：

#study-OpenResty/example/05-nginx-lua-module-readvar
worker_processes  1;        #nginx worker 数量
error_log logs/error.log;   #指定错误日志文件路径
events {
  worker_connections 1024;
}

http {
     server {
         listen 6699;
         location / {
             set $my_var 'my_var';
             content_by_lua_block {
                 local response = {}
                 response[1]= ngx.var.request_uri;
                 response[2]=";"
                 response[3] = ngx.var.my_var;
                 ngx.say(response);
             }
         }
     }
 }

返回结果如下：

$ curl 127.0.0.1:6699/
/;my_var

如果使用其它的uri，返回结果一同变化：

$ curl "127.0.0.1:6699/abcdef?a=1&b=2"
/abcdef?a=1&b=2;my_var

创建并使用共享内存

ngx.shared是一个table，记录在nginx.conf中用指令lua_shared_dict创建的共享内存。

譬如在nginx.conf中用lua_shared_dict指定创建一个5兆大小的共享内存：

...
lua_shared_dict kong                5m;

然后就可以在lua代码中，用ngx.shared读取这块共享内存，有两种语法格式：

dict = ngx.shared.kong
dict = ngx.shared[kong]

共享内存的操作方法有多个，详细用法参考ngx.shared：

get
get_stale
set
safe_set
add
safe_add
replace
delete
incr
lpush
rpush
lpop
rpop
llen
ttl
expire
flush_all
flush_expired
get_keys
capacity
free_space

这些方法都是原子操作，可以在多个nginx worker中并发调用。

使用方法如下，创建了一个大小为10M，名为dogs的共享内存，请求/set时，在共享内存中写入数据，请求/get时，从共享内存中读取数据：

#study-OpenResty/example/04-nginx-lua-module-shared-mem
worker_processes  1;        #nginx worker 数量
error_log logs/error.log;   #指定错误日志文件路径
events {
  worker_connections 1024;
}

 http {
     lua_shared_dict dogs 10m;
     server {
         listen 6699;
         location /set {
             content_by_lua_block {
                 local dogs = ngx.shared.dogs
                 dogs:set("Jim", 8)
                 ngx.say("STORED")
             }
         }
         location /get {
             content_by_lua_block {
                 local dogs = ngx.shared.dogs
                 ngx.say(dogs:get("Jim"))
             }
         }
     }
 }

请求/set时：

$ curl 127.0.0.1:6699/set
STORED

请求/get时：

$ curl 127.0.0.1:6699/get
8

参考

编程基础系统基础关注跟踪

Kubernetes Prometheus 超级账本

openresty

Web开发平台OpenResty（四）: 项目开发中常用的操作

目录

说明

打印日志

读取nginx的内置变量

创建并使用共享内存

参考

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