灰度发布-Openresty+lua实现动态upstream，


动态的负载均衡控制；
平滑上下线服务，升级服务；
高可能保证–自动踢离线服务下线；
具体思路
利用lua中 "lua_shared_dict" 指令开辟一个共享内存空间;
通过API动态根据key值&参数修改 upstream (这里使用 host 作为key);
利用 proxy_pass 可使用变量特性及lua指令 "set_by_lua" 动态修改当前 upstream 变量即可；
配置：

worker_processes  1;
pid        logs/nginx.pid;
events {
    worker_connections  1024;
}
 
http {
    include       mime.types;
    default_type  application/octet-stream;
 
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for"';
    sendfile        on;
 
    keepalive_timeout  65;
          
    #lua_shared_dict upstreams 1m;  # 声明一个ngx多进程全局共享内存区域，_G 作为基于shm的Lua字典的存储空间ngx.shared.<name>   
    lua_shared_dict _ups_zone 64m; # 定义upstream共享内存空间
 
 
        
    upstream backend {                        # 配置后端服务器组
                server 127.0.0.1:18084;
                server 127.0.0.1:18083;
    }
 
    server {
        listen       8000;
        server_name  localhost;
 
        access_log  logs/80.access.log  main;
        error_log   logs/80.error.log error;
 
 
#更新API接口
        location = /ups_update {  
            content_by_lua '  
                local ups = ngx.req.get_uri_args()["ups"]  
                if ups == nil then 
                    ngx.say("usage: /ups_update?ups=x.x.x.x")  
                    return 
                end  
                local host = ngx.var.http_host  
                local ups_from = ngx.shared._ups_zone:get(host);  
                ngx.log(ngx.WARN, host, " update upstream from ", ups_from, " to ", ups)  
                ngx.shared._ups_zone:set(host, ups);  
                ngx.say(host, " update upstream from ", ups_from, " to ", ups)  
            ';  
        }
 
location / {  
            # 动态设置当前 upstream, 未设置则使用默认 upstream  
            set_by_lua $cur_ups '  
                local ups = ngx.shared._ups_zone:get(ngx.var.http_host)  
                if ups ~= nil then 
                    ngx.log(ngx.ERR, "get [", ups, "] from ngx.shared._ups_zone")  
                    return ups  
                end  
                --ngx.log(ngx.INFO, "use default upstream");  
                return "qq_backend";  
            '  
            proxy_next_upstream off;  
            proxy_set_header    Host $host;  
            proxy_http_version  1.1;  
            proxy_set_header    Connection  "";  
            proxy_pass $scheme://$cur_ups;  
        }
 
 
}
 

}

测试切换upstream的backend效果：
1、默认情况【请求4次】：

root@ubuntu:~# curl  127.0.0.1:8000
83 server
root@ubuntu:~# curl  127.0.0.1:8000
84 server 
root@ubuntu:~# curl  127.0.0.1:8000
83 server
root@ubuntu:~# curl  127.0.0.1:8000
84 server

切换upstream

root@ubuntu:~# curl  127.0.0.1:8000/ups_update?ups=127.0.0.1:18083
127.0.0.1:8000 update upstream from 127.0.0.1:18083 to 127.0.0.1:18083
root@ubuntu:~# curl  127.0.0.1:8000
83 server
root@ubuntu:~# curl  127.0.0.1:8000
83 server
root@ubuntu:~# curl  127.0.0.1:8000
83 server
root@ubuntu:~# curl  127.0.0.1:8000
83 server

切换upstream:

worker_processes  1;
pid        logs/nginx.pid;
events {
    worker_connections  1024;
}
 
http {
    include       mime.types;
    default_type  application/octet-stream;
 
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for"';
    sendfile        on;
 
    keepalive_timeout  65;
          
    lua_shared_dict upstreams 1m;  # 声明一个ngx多进程全局共享内存区域，_G 作为基于shm的Lua字典的存储空间ngx.shared.<name>   
    upstream default_upstream {                        # 配置后端服务器组
                server 127.0.0.1:18081;
                server 127.0.0.1:18082;
    }
         
    upstream lua_upstream {                        # 配置后端服务器组
                server 127.0.0.1:18084;
                server 127.0.0.1:18083;
    }
 
    server {
        listen       8000;
        server_name  localhost;
 
        access_log  logs/80.access.log  main;
        error_log   logs/80.error.log error;
 
        location = /_switch_upstream {
             content_by_lua_block{
                    local ups = ngx.req.get_uri_args()["upstream"]
                    if ups == nil or ups == "" then
                        ngx.say("upstream is nil 1")
                        return nil
                    end
                    local host = ngx.var.http_host
                    local upstreams = ngx.shared.upstreams
                    local ups_src = upstreams:get(host)
                    ngx.say("Current upstream is :",ups_src)
                    ngx.log(ngx.WARN, host, " change upstream from ", ups_src, " to ", ups)
                    local succ, err, forcible = upstreams:set(host,  ups)
                    ngx.say(host, " change upstream from ", ups_src, " to ", ups)
            }
        }
         
        location / {
            set_by_lua_block $my_upstream {
                local ups = ngx.shared.upstreams:get(ngx.var.http_host)
                if ups ~= nil then
                    ngx.log(ngx.ERR, "get [", ups,"] from ngx.shared")
                    return ups
                end
                return "default_upstream"
            }
 
            proxy_next_upstream off;
            proxy_set_header    X-Real-IP           $remote_addr;
            proxy_set_header    X-Forwarded-For     $proxy_add_x_forwarded_for;
            proxy_set_header    Host                $host;
            proxy_http_version  1.1;
            proxy_set_header    Connection  "";
            proxy_pass          http://$my_upstream ;
        }
    }   
 
   
}

切换：

curl 127.0.0.1:8000/_switch_upstream?upstream=lua_upstream
curl 127.0.0.1:8000/_switch_upstream?upstream=default_upstream

这里用的还是静态文件，改成tomcat服务之后也是可以进行代理的切换。要是想持久化的话 ，得用到redis。

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