Cannot use connect.compress() middleware with http-proxy

Created by: fmarier

Looking at the middleware example that comes with http-proxy:

https://github.com/nodejitsu/node-http-proxy/blob/1df2b30e84f078d86e744601bd6fc59381a1c7b3/examples/middleware/gzip-middleware.js

I decided to write my own program which makes use of connect.compress() but is otherwise the same as the example that comes with http-proxy:

https://github.com/fmarier/node-compressed-http-proxy/blob/master/compress-example.js

Unfortunately, it doesn't work because the compress middleware looks at the headers before they are written out in order to decide whether or not a resource should be compressed. I can force compress to always compress everything by calling it like this:

connect.compress({filter: function () {return true;}})

but that's of course not a good idea since images will get gzipped too.

The result is that proxied content is never compressed by connect.compress().