Move the proxy DNS resolver code into gateway/src/resty/resolver/http…

….lua

To avoid having to call a resolver when used with proxies, all DNS resolution
should happen inside the connect() method

gateway/src/resty/http/proxy.lua

@@ -58,12 +58,12 @@ local function connect(request, skip_https_connect)
             proxy_uri.port = default_port(proxy_uri)
         end
 
-        -- Resolve the proxy IP/Port
-        local proxy_host, proxy_port = httpc:resolve(proxy_uri.host, proxy_uri.port)
-        local proxy_url = format("%s://%s:%s", proxy_uri.scheme, proxy_host, proxy_port)
+        local proxy_url = format("%s://%s:%s", proxy_uri.scheme, proxy_uri.host, proxy_uri.port)
         local proxy_auth = request.proxy_auth
 
         if scheme == 'http' then
+            -- Used by http_ng module to send request to 3scale backend through proxy.
+
             -- http proxy needs absolute URL as the request path, lua-resty-http 1.17.1 will
             -- construct a path_prefix based on host and port so we only set request path here
             --
@@ -110,6 +110,7 @@ local function connect(request, skip_https_connect)
         ngx.log(ngx.DEBUG, 'targeting server ', host, ':', port)
     else
         -- Connect direct
+        -- Mostly used by http_ng module to connect 3scale backend module.
         local ok, err = httpc:connect(options)
         if not ok then return nil, err end
 

gateway/src/resty/resolver/http.lua

@@ -1,6 +1,8 @@
 local resty_http = require 'resty.http'
 local resty_resolver = require 'resty.resolver'
 local round_robin = require 'resty.balancer.round_robin'
+local url_helper = require('resty.url_helper')
+local format = string.format
 
 local setmetatable = setmetatable
 
@@ -53,6 +55,21 @@ function _M.connect(self, options, ...)
     ip, real_port = self:resolve(options.host, options.port)
     options.host = ip
     options.port = real_port
+  else
+    local uri, err = url_helper.parse_url(proxy)
+    if not uri then
+        return nil, 'invalid proxy ' .. err
+    end
+
+    -- Resolve the proxy IP/Port
+    local proxy_host, proxy_port = self:resolve(uri.host, uri.port)
+    local proxy_url = format("%s://%s:%s", uri.scheme, proxy_host, proxy_port)
+
+    if proxy_opts.http_proxy then
+      options.proxy_opts.http_proxy =  proxy_url
+    elseif proxy_opts.https_proxy then
+      options.proxy_opts.https_proxy =  proxy_url
+    end
   end
 
   local ok, err = resty_http.connect(self, options, ...)