OpenResty体验

官网:https://openresty.org/cn/download.html

本文使用docker来部署环境

一、运行Docker容器，暴露80端口，然后通过宿主机IP:80即可访问容器里的OpenResty

docker run -itd --name openresty -p 8000:80 openresty/openresty:centos

二、进入容器

docker exec -it $(docker ps -f "name=openresty" -q) bash

#docker ps -f "name=openresty" -q是-f过滤条件，筛选出docker run指定的name，-q是只打印container id，将结果给docekr exec 执行

三、修改配置

openresty的文件在/usr/local/openresty/
nginx.conf配置文件在/usr/local/openresty/nginx/conf/nginx.conf，该配置文件include /etc/nginx/conf.d/*.conf，因此可在/etc/nginx/conf.d/创建你自己的配置文件。
执行命令：

vi /etc/nginx/conf.d/default.conf

将default.conf内容修改为:(注意upstream改为提供api接口的服务器，比如tomcat)

upstream tomcat {
    server 127.0.0.1:8080;
    server 127.0.0.1:8081;
    server 127.0.0.1:8082 backup;
}

server {
    listen       80;
    server_name  localhost;

    #charset koi8-r;
    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        root   /usr/local/openresty/nginx/html;
        index  index.html index.htm;
    }

    location /f/ {
        proxy_pass http://tomcat/;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
    }

    #error_page  404              /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/local/openresty/nginx/html;
    }

}

reload配置，执行命令：

openresty -s reload

在宿主机执行curl "localhost:8000/f/xxx"(xxx替换为tomcat服务端提供的接口名)

四、健康检查

作为上层，需要感知底层upstream服务是否可用，如果server down了必须摘除，不再将请求转发到该upstream server上。因此需做健康检查，也即是探活。
健康检查的作用有两个：
1.保证后端服务高可用，请求不会落到down掉的机器；
2.优雅地上下线，将要上线的机器设置为OpenResty认为机器down的状态，保证请求不会再落到该机器，然后就可以进行一顿操作之后再让其恢复up的状态
简单的做法是让upstream后端服务提供一个/status接口，该接口的HTTP状态有两种：200和503，接口维护一个boolean变量，true则将接口状态改为200，否则改为503。OpenResty定时进行健康检查，调用该接口，返回HTTP状态是200则认为机器up，否则是down。
健康模块：https://github.com/openresty/lua-resty-upstream-healthcheck
步骤：

vi /etc/nginx/conf.d/default.conf

假设现在部署了3个api服务，都提供/status接口，将default.conf修改为

lua_package_path "/path/to/lua-resty-upstream-healthcheck/lib/?.lua;;";

# sample upstream block:
upstream foo.com {
    server 127.0.0.1:12354;
    server 127.0.0.1:12355;
    server 127.0.0.1:12356 backup;
}

# the size depends on the number of servers in upstream {}:
lua_shared_dict healthcheck 1m;

lua_socket_log_errors off;

init_worker_by_lua_block {
    local hc = require "resty.upstream.healthcheck"

    local ok, err = hc.spawn_checker{
        shm = "healthcheck",  -- defined by "lua_shared_dict"
        upstream = "foo.com", -- defined by "upstream"
        type = "http",

        http_req = "GET /status HTTP/1.0\r\nHost: foo.com\r\n\r\n",
                -- raw HTTP request for checking

        interval = 2000,  -- run the check cycle every 2 sec
        timeout = 1000,   -- 1 sec is the timeout for network operations
        fall = 3,  -- # of successive failures before turning a peer down
        rise = 2,  -- # of successive successes before turning a peer up
        valid_statuses = {200},  -- a list valid HTTP status code，可用逗号分隔多个有效状态
        concurrency = 10,  -- concurrency level for test requests
    }
    if not ok then
        ngx.log(ngx.ERR, "failed to spawn health checker: ", err)
        return
    end
}

server {
    listen       80;
    server_name  localhost;

    #charset koi8-r;
    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        root   /usr/local/openresty/nginx/html;
        index  index.html index.htm;
    }

    location /f/ {
        proxy_pass http://foo.com/;  
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
    }

    #error_page  404              /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/local/openresty/nginx/html;
    }

}

然后检查配置是否正确，执行命令：

openresty -t

接着reload

openresty -s reload