内网通过K8S搭建多个分支测试环境，可是如果外网需要访问而且域名都是一致的情况下，这个时候变得麻烦了。如何通过不同的请求参数访问不同的后端环境呢，答案是可以的，通过lua可以达到。

入口:
http://fengwan.blog.51cto.com/?envs=branches #branches环境
http://fengwan.blog.51cto.com/?envs=branchesv2 #branchesv2环境

另外考虑到APP请求的时候无法通过参数来处理，我们可以添加统一的请求header: envs
curl --header "envs:branches" http://fengwan.blog.51cto.com
curl --header "envs:branchesv2" http://fengwan.blog.51cto.com

我们通过Openresty判断头部然后选择不同的后端环境
Nginx配置:

    upstream branches {
        server 10.254.220.47:80;
    }
    upstream branchesv2 {
        server 10.254.60.225:80;
    }

    upstream default {
        server  10.254.220.47:80;
    }
            server {
        listen       80;
        server_name  fengwan.blog.51cto.com;
        location / {
                lua_code_cache on;
                set $upstreamhost "";
                rewrite_by_lua_file /etc/nginx/conf.d/html/proxy.lua;

                            proxy_redirect off ;
               proxy_set_header Host $host;
               proxy_set_header X-Real-IP $remote_addr;
               proxy_set_header REMOTE-HOST $remote_addr;
               proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
               client_max_body_size 50m;
               client_body_buffer_size 256k;
               proxy_connect_timeout 30;
               proxy_send_timeout 30;
               proxy_read_timeout 60;
               proxy_buffer_size 256k;
               proxy_buffers 4 256k;
               proxy_busy_buffers_size 256k;
               proxy_temp_file_write_size 256k;
               proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;
               proxy_max_temp_file_size 128m;

                proxy_pass http://$upstreamhost;
        }
   }

lua脚本内容
/etc/nginx/conf.d/html/proxy.lua;

local request_method = ngx.var.request_method
local args = nil
local param = nil
local param2 = nil

if "GET" == request_method then
    args = ngx.req.get_uri_args()
elseif "POST" == request_method then
    ngx.req.read_body()
    args = ngx.req.get_post_args()
end

if ngx.var.cookie_envs == 'branches' then
        ngx.var.upstreamhost = "branches"
elseif ngx.var.cookie_envs == 'branchesv2' then
        ngx.var.upstreamhost = "branchesv2"
end

if not args or not args["envs"] then
        if not ngx.req.get_headers()['envs'] then
                ngx.var.upstreamhost = "tags"
        elseif ngx.req.get_headers()['envs'] == 'branches' then
                ngx.var.upstreamhost = "branches"
        elseif ngx.req.get_headers()['envs'] == 'branchesv2' then
                ngx.var.upstreamhost = "branchesv2"
        else
                ngx.var.upstreamhost = "tags"
        end
elseif args["envs"] == 'branches' then
        ngx.header["Set-Cookie"]= "envs=branches; path=/"
        ngx.var.upstreamhost = "branches"
elseif  args["envs"] == 'branchesv2' then
        ngx.header["Set-Cookie"]= "envs=branchesv2; Path=/"
        ngx.var.upstreamhost = "branchesv2"
end