Add option to pass through compressed responses

README.md

@@ -65,6 +65,14 @@ If you'd like to bypass SSL verification
 reverse_proxy "http://localhost:8000", verify_ssl: false
 ```
 
+If you'd like to allow the proxy to request compressed resources by forwarding the `Accept-Encoding` header
+
+```ruby
+reverse_proxy "http://localhost:8000", compression: :passthrough
+# Note that your controller's response will only be compressed
+# if the original response from localhost:8000 is compressed!
+```
+
 If you'd like to customize the options passed into the [HTTP session](https://ruby-doc.org/stdlib-2.4.0/libdoc/net/http/rdoc/Net/HTTP.html#start-method)
 
 ```ruby

lib/reverse_proxy/client.rb

@@ -43,7 +43,8 @@ module ReverseProxy
         path:        nil,
         username:    nil,
         password:    nil,
-        verify_ssl: true
+        verify_ssl:  true,
+        compression: :disabled
       )
 
       source_request = Rack::Request.new(env)
@@ -73,11 +74,14 @@ module ReverseProxy
       # Hold the response here
       target_response = nil
 
-      # Don't encode response/support compression which was
-      # causing content length not match the actual content
-      # length of the response which ended up causing issues
-      # within Varnish (503)
+      case options[:compression]
+      when :passthrough
+        # Pass along the "Accept-Encoding" header from the source request as-is,
+        # so we don't need to change anything
+      when :disabled, false, nil
+        # Remove the "Accept-Encoding" header if compression is disabled
         target_request['Accept-Encoding'] = nil
+      end
 
       http_options = {}
       http_options[:use_ssl] = (uri.scheme == "https")