Hacker News Reader

Comment by judofyr | Hacker News Reader

Yes, please. I've never understood why someone wants to do pub/sub and only base the reliability on TCP/WebSockets. The concept of "fire and hope everyone who wants the message still has a connection open" always seemed fragile to me.

This has been the reason I've recommended implementing long-polling instead of WebSockets for real-time applications. And every time I see a real-time solution which only uses WebSockets I try to steer away from it. Once you have a reliable data model (which includes log position, retrieving old messages etc.) it's just as simple to implement long-polling as WebSockets. With WebSockets-only solution I can't help but think they base all the message delivery reliability on TCP.

This proposal looks like a clean (very Redis-like) solution, and I immediately see use cases for it.

View on HN

Did you look into the EventSource API? It's basically automatic long-polling with a simple file format built into the browser. It supports pretty much every "real-time" pattern: regular polling, long polling, and streaming.

The browser handles the log position for you (via the id field and the Last-Event-ID header) and automatically reconnects when the server closes the stream or the connection is lost.

The proposed Redis API seems to fit extremely well to this model. My previous usage of EventSource with Redis worked by sending the entire state whenever someone (re-)connects and using PubSub afterwards. This works well for me, but likely doesn't scale very well.

Server-Sent Event (SSE) is very underrated HTML5 technology.

If you dont need bi-directional realtime messaging, use SSE.

The only big barrier to adopting the EventSource API is the complete lack of support from Microsoft's browsers: http://caniuse.com/#feat=eventsource

Fortunately, polyfilling is fairly easy, e.g. https://github.com/Yaffle/EventSource.

Take a look at SSE (Server-Sent Events, aka EventSource). Unlike WebSockets, the it has the concept of an "event ID", which allows the protocol to automatically continue from the last event, no extra roundtrip needed to send a setup message to the server. Implemented by every major browser (except, of course, IE, where you can polyfill it pretty easily).

This is exactly what we built for Poll Everywhere with http://firehose.io/ to push updates in realtime reliably over crappy wifi connections. Since we're used by presenters at huge conferences with dicey networks we had to spend a lot of time thinking through all sorts of low quality connection scenarios.

It's exciting to see a proposal for an all-Redis implementation.

Reply on news.ycombinator.com