lua-modfin-srv-proxy

A dynamic SRV record proxy replacing nginx proxy_pass and static upstreams built for OpenResty / ngx_lua.

It was design to work together with DNS services like consul

Status

A first implementation is ready for testing. It seams ready for at least simpler use cases.

Features

• Multiple resolvers
• Custom resolver port
• SRV and A record caching
• HTTP proxying
• Proxying selection strategies
  • Round Robin
  • Random
  • IP Hashing

Dependencies

• ngx_lua
• resty.dns.resolver
• cjson
• resty.http (not included in OpenResty)

Config

Using OpenResty it should be fairly straight forward to implement.

• Add resty.http lua files to your lualib dir, eg. /usr/local/openresty/lualib/resty/
• Add modfin.srv_proxy lua file to your lualib dir, eg. /usr/local/openresty/lualib/modfin/

Nginx config example

    lua_shared_dict srv_proxy_cache 2m;                           
    server {
        location /api/a-backend {

            set $srv_resolvers "8.8.8.8 127.0.0.1 192.168.2.6:8600";  
            set $srv_service "_a-backend._http.service.consul";       

            rewrite /api/a-backend/(.*) /$1  break;

            content_by_lua "
                     local proxy = require 'modfin.srv_proxy'                              
                     proxy.set('resolvers', ngx.var.srv_resolvers)
                     proxy.pass(ngx.var.srv_service)                                      
            ";

        }
        listen 80;
    }

#API

set

syntax:proxy.set("key", "value") It is used to set settings for the srv-proxy

• "resolvers" - ip addresses to the resolvers used
• "ttl" - The ttl in seconds for the cached srv records. DNS ttl is ignored (default 60)
• "strategy" - The proxy strategy. "round_robin", "random", "ip_hash" (default "round_robin")
• "dns_protocol" - "udp", "tcp" (default "udp")
• "dns_timeout" - in ms (default 200)
• "dns_retrys" - number of retrys if timeout exp (default 2)
• "http_timeout" - in ms, timeout establishing a connection (default 500)
• "proxy_timeout" - in ms, timeout for backend to produce output (default 2000)

pass

symtax: proxy.pass("_a-servic._protocol.domain")

Starts the process of and sets the content of the nginx response.

TODO

• Testing, non implemented yet
• Implementing other selection strategies, using weights and priority. Maybe something with server location as well