1、系统基础设计图为：

用户通过Http访问Openresty（Nginx + Lua）， 其中Nginx虚拟主机中配置文件进行Lua脚本加载。

LUA通过nginx内置变量或者http请求中变量来区分不同集群，使用LUA脚本从redis中获取所属集群。

然后通过反向代理到对应集群。

2、 Openresty配置

Nginx主配置文件：

 1 user nginx;
 2 worker_processes  4;
 3 pid        logs/nginx.pid;
 4 
 5 worker_rlimit_nofile 1000000;
 6 
 7 events {
 8     use epoll;
 9     worker_connections  65535;
10 }
11 
12 http {
13     lua_package_path "/usr/local/openresty/lualib/resty/lrucache/?.lua;;";   # 加载lua自定义模块。
14     include       mime.types;
15     default_type  application/octet-stream;
16     log_format  main  '$remote_addr - $remote_user [$time_local] $request $http_host '
17                       '$status $body_bytes_sent $http_referer '
18                       '"$http_user_agent" $http_x_forwarded_for '
19                       '$upstream_addr $upstream_status $upstream_cache_status '
20               '$upstream_response_time $request_time';
21     access_log logs/access.log main;
22     error_log logs/error.log;
23     sendfile        on;
24     tcp_nopush     on;
25     max_ranges  1;
26     keepalive_timeout  120;
27     gzip  on;
28     gzip_min_length 1k;
29     gzip_buffers 4 16k;
30     gzip_comp_level 2;
31     gzip_types application/x-www-form-urlencoded application/pdf text/plain application/x-javascript application/javascript text/css application/xml application/json;
32     client_max_body_size 22m;
33     client_body_buffer_size  1024k;
34     client_header_buffer_size  1024k;
35     underscores_in_headers on;
36 
37         location /status {
38             stub_status on;
39             access_log off;
40             allow 127.0.0.1;
41             deny all;
42         }
43     }
44     include /data/work/conf/conf.d/*/*.conf;

虚拟主机的配置：

 1 server {
 2     listen 80;
 3     server_name 域名;
 4     access_log  logs/access_80.log main;
 5     error_log  logs/error_80.log;
 6 
 7 
 8     location / {
 9     resolver DNS的IP地址 valid=3600;   如果配置文件中使用了域名，需要此配置，不然无法解析DNS。
10         set $url '';  定义变量
11         set $upstream_port '80';  变量赋值
12         rewrite_by_lua_file lua/get_upstream_url.lua;   加载lua脚本
13     proxy_pass http://$url$request_uri;
14     proxy_http_version 1.1;
15     proxy_set_header Upgrade $http_upgrade;
16     proxy_set_header connection "keep-alive";
17     proxy_set_header Host $host;
18     proxy_set_header X-Forwarded-Port $server_port;
19     proxy_set_header X-Forwarded-For $remote_addr;21     proxy_set_header X-Real-IP $remote_addr;
22     proxy_read_timeout 300;
23     proxy_send_timeout 300;
24     proxy_connect_timeout 90;
25     proxy_temp_file_write_size 10240k;
26     }
27 }

lua 脚本

local localCache = require("mycache")  本地缓存配置
local localRes, err = localCache.get(ngx.var.host)
if localRes ~= nil then
    ngx.var.url = localRes .. ":" .. ngx.var.upstream_port
    return
else
    local redis = require "resty.redis"
    local red = redis:new()
    red:set_timeout(1000)
    local ok, err = red:connect("redis地址", 6379)
    if not ok then
        ngx.log(ngx.ERR, "failed to connect: ", err)
        return
    end
    local res, err = red:hget("hosts", ngx.var.host)
    if not res then
        ngx.log(ngx.ERR, "failed to get host: ", err)
        return
    end
    if res == ngx.null then
        ngx.log(ngx.ERR, "host not found.")
        ngx.var.url = "异常网址"
           return
    else
        localCache.set(ngx.var.host, res)
        ngx.var.url = res .. ":" .. ngx.var.upstream_port
    end
    local ok, err = red:set_keepalive(10000, 100)
    if not ok then
       ngx.log(ngx.ERR, "failed to set keepalive: ", err)
       return
    end
end

自定义本地缓存的lua模块脚本

 1 local _M = {}
 2 
 3 local lrucache = require "resty.lrucache"
 4 
 5 local c, err = lrucache.new(10000) 
 6 if not c then
 7     return error("failed to create the cache: " .. (err or "unknown"))
 8 end
 9 
10 function _M.get(host)
11     local key = c:get(host)
12     return key
13 end
14 
15 function _M.set(host, key)
16     c:set(host, key, 3600)
17     local res = c:get(host)
18 end
19 
20 return _M