Show HN: Pushpin, a reverse proxy for real-time web services

As an example of how powerful Pushpin's transparency is, we were able to build a Bayeux server with it. Bayeux is the open pubsub standard supported by projects such as Faye [1].

For our Bayeux server, we made a backend that uses Pushpin's ZeroMQ interface to set up stateless long-polling and manage stateful WebSockets (eventually I want to figure out how to use Pushpin's stateless WebSockets ability here, but the Bayeux protocol makes this difficult). Session information is stored in Redis. Pushpin's JSONP configuration is tweaked to work exactly like Bayeux's, which is generally needed for the initial handshake. When a message needs to be published to all subscribers of a channel, it is produced once by the backend and Pushpin handles the one-to-many delivery. Long-polling responses use Pushpin's JSON Patch ability, so that they can contain the request-specific ack information without published payloads needing to be client-specific. Thus, we were able to make Pushpin speak Bayeux without it having any direct knowledge of that protocol.

Most developers will not need to build such a gnarly service like this, as modern realtime APIs tend to be a lot simpler than the classic Bayeux protocol. But I think it's a cool example of what's possible.

[1] http://faye.jcoglan.com/