OpenResty(nginx+lua) 入门

OpenResty 官网：http://openresty.org/

OpenResty 是一个nginx和它的各种三方模块的一个打包而成的软件平台。最重要的一点是它将lua/luajit打包了进来，使得我们可以使用lua脚本来进行web的开发。有了lua，我们可以借助于nginx的异步非阻塞的功能，达到使用 lua 异步并发访问后端的 MySQL, PostgreSQL, Memcached, Redis等等服务。特别是特有的 ngx.location.capture_multi 功能让人印象深刻，其可以达到极大的减少浏览器的http连接数量，并且可以异步并发的访问后台 Java/PHP/Python 等等接口。OpenResty 架构的web可以轻松超越Node.js的性能，并且对后端语言没有限制，你可以使用Java/PHP/Python等等各种语言。OpenResty(nginx+lua)可以替代node.js的前端渲染的功能。

OpenResty (aka. ngx_openresty) is a full-fledged web application server by bundling the standard Nginx core, lots of 3rd-party Nginx modules, as well as most of their external dependencies.

By taking advantage of various well-designed Nginx modules, OpenResty
effectively turns the nginx server into a powerful web app server, in
which the web developers can use the Lua programming language to script
various existing nginx C modules and Lua modules and construct extremely
high-performance web applications that are capable to handle 10K+
connections.

OpenResty aims to run your server-side web app
completely in the Nginx server, leveraging Nginx's event model to do
non-blocking I/O not only with the HTTP clients, but also with remote
backends like MySQL, PostgreSQL, Memcached, and Redis.

1. 安装OpenResty

先安装依赖：yum install readline-devel pcre-devel openssl-devel gcc

解压： tar zxvf ngx_openresty-1.9.3.1.tar.gz

建立一个软连接：ln -s ngx_openresty-1.9.3.1 openresty

进入目录：cd openresty

编译：

./configure \
--with-cc-opt="-I/usr/local/include" \
--with-ld-opt="-L/usr/local/lib" \
--prefix=/opt/openresty

... ...
Configuration summary
+ using system PCRE library
+ using system OpenSSL library
+ md5: using OpenSSL library
+ sha1: using OpenSSL library
+ using system zlib library

nginx path prefix: "/opt/openresty/nginx"
nginx binary file: "/opt/openresty/nginx/sbin/nginx"
nginx configuration prefix: "/opt/openresty/nginx/conf"
nginx configuration file: "/opt/openresty/nginx/conf/nginx.conf"
nginx pid file: "/opt/openresty/nginx/logs/nginx.pid"
nginx error log file: "/opt/openresty/nginx/logs/error.log"
nginx http access log file: "/opt/openresty/nginx/logs/access.log"
nginx http client request body temporary files: "client_body_temp"
nginx http proxy temporary files: "proxy_temp"
nginx http fastcgi temporary files: "fastcgi_temp"
nginx http uwsgi temporary files: "uwsgi_temp"
nginx http scgi temporary files: "scgi_temp"

其中 --prefix=/opt/openresty 指定了安装目录，不指定的话默认会安装到 /usr/local/openresty 目录下。

编译安装： make && make install

[root@localhost src]# cd /opt/openresty/
[root@localhost openresty]# ls
bin  luajit  lualib  nginx

可以看到 /opt/openresty 目录下四个文件夹，其中包括了 luajit，nginx。

启动openresty: /opt/openresty/nginx/sbin/nginx -c /opt/openresty/nginx/conf/nginx.conf -p /opt/openresty/nginx/

[root@localhost src]# ps -elf|grep nginx
1 S root      2076     1  0  80   0 - 34999 -      21:24 ?        00:00:00 nginx: master process /opt/openresty/nginx/sbin/nginx -c /opt/openresty/nginx/conf/nginx.conf -p /opt/openresty/nginx/
5 S nobody    2077  2076  0  80   0 - 35045 -      21:24 ?        00:00:00 nginx: worker process
0 S root      2079  1678  0  80   0 -  1088 -      21:24 pts/1    00:00:00 grep nginx

验证可以访问： curl 127.0.0.1

2. content_by_lua 和 content_by_lua_file

nginx 如何嵌入 lua 脚本。方法就是在nginx的配置文件nginx.conf 中使用 content_by_lua 或者 cotent_by_lua_file 指令：

1) content_by_lua 一般在很简单的lua脚本时使用：

location /lua {
set $test "hello, world.";
content_by_lua '
ngx.header.content_type = "text/plain";
ngx.say(ngx.var.test);
';
}

访问 http://localhost/lua 可以看到输出到页面的 hello, world.

2）cotent_by_lua_file 适应于复杂的 lua 脚本，专门放入一个文件中：

location /lua2 {
#lua_code_cache off;
content_by_lua_file lua/hello.lua;
}

路径相对于 /opt/openresty/nginx

[root@localhost lua]# pwd
/opt/openresty/nginx/lua
[root@localhost lua]# cat hello.lua
ngx.say('hello ngx_lua!!!!');

本例子中 hello.lua 只包含一句： ngx.say('hello ngx_lua!!!!');

访问 /lua2 :

[root@localhost lua]# curl localhost/lua
hello ngx_lua!!!!

可以看到访问成功。

在 nginx.conf 文件的 server {.. ...} 中加入 lua_code_cache off; 可以方便调试lua脚本，修改lua脚本之后，不需要 reload nginx.

openresty 中的 nginx 嵌入 luajit 的原理：

[root@localhost lua]# cat cache_lock.lua
local redis = require "resty.redis"
local red = redis:new()
local resty_lock = require "resty.lock"
local ngx_cache = ngx.shared.ngx_cache

function set_to_cache(key, value, exptime)
if not exptime then
exptime = 0
end
local succ, err, forcible = ngx_cache:set(key, value, exptime)
return succ
end

function get_from_cache(key)
local ngx_cache = ngx.shared.ngx_cache;
local value = ngx_cache:get(key)
if not value then       -- cache miss
local lock = resty_lock:new("cache_lock")
local elapsed, err = lock:lock(key)
if not elapsed then
return fail("failed to acquire the lock: ", err)
end

value = get_from_redis(key)
if not value then
local ok, err = lock:unlock()
if not ok then
return fail("failed to unlock: ", err)
end
ngx.say("no value found")
return
end

local ok, err = ngx_cache:set(key, value, 1)
if not ok then
local ok, err = lock:unlock()
if not ok then
return fail("failed to unlock: ", err)
end
return faile("failed to update ngx_cache: ", err)
end

local ok, err = lock:unlock()
if not ok then
return faile("failed to unlock: ", err)
end

return value
end

ngx.say("get from cache.")
return value
end

function get_from_redis(key)
red:set_timeout(1000)

local ok, err = red:connect("127.0.0.1", 6379)
if not ok then
ngx.say("failed to connect: ", err)
return
end

local res, err = red:get(key)
if not res then
ngx.say("failed to get doy: ", err)
return ngx.null
end

ngx.say("get from redis.")
return res
end

function set_to_redis(key, value)
red:set_timeout(1000)
local ok, err = red:connect("127.0.0.1", 6379)
if not ok then
ngx.say("failed to connect: ", err)
return
end

local ok, err = red:set(key, value)
if not ok then
ngx.say("failed to set to redis: ", err)
return
end
return ok
end

set_to_redis('dog', "Bob")
local rs = get_from_cache('dog')
ngx.say(rs)

View Code
测试：

[root@localhost lua]# curl localhost/cache_lock
get from cache.
Bob
[root@localhost lua]# curl localhost/cache_lock
get from cache.
Bob

7. openresty 执行阶段

nginx的执行阶段分成了很多个阶段,所以第三方模块就可以在某个适当的阶段加入一些处理。openresty进行了简化成了7个阶段：



7个阶段的执行顺序如下：

set_by_lua: 流程分支判断，判断变量初始哈

rewrite_by_lua: 用lua脚本实现nginx rewrite

access_by_lua: ip准入，是否能合法性访问，防火墙

content_by_lua: 内存生成

header_filter_by_lua：过滤http头信息，增加头信息

body_filter_by_lua: 内容大小写，内容加密

log_by_lua: 本地/远程记录日志

但是其实我们可以只用 content_by_lua，所有功能都在该阶段完成，也是可以的。