XMPP over websockets [HTML5] | Hacker News Reader

XMPP over websockets [HTML5]

blog.superfeedr.com

76 pointsjulien28 comments

> it’s by far the greatest protocol to “push” content from a server to client

Except it's messy and ugly. Well, it's somehow feels on par with HTML, where browsers have to support all sorts of weirdness, though. Further reading: http://news.ycombinator.com/item?id=2069810

As a big fan of and small contributor to ejabberd (I run im.wordpress.com), one who has used Jack's excellent strophe.js, and one who is anxious to see websockets in more use cases, I was pleased to read this news.

However, I still consider XMPP as the protocol of last resort when designing apps for the browser that don't map perfectly onto XMPP. I would sooner write a new protocol than set up a new ejabberd cluster. (This opinion is based on the quality of documentation available a year ago and may be out of date.)

Don't confuse the protocol and the server! It may be tricky to setup and ejabberd cluster, but you can't blame XMPP for that!

Also, I wish people were more adventurous with XMPP in general and stop thinking that it's just a chat protocol.

We're actually thinking of using XMPP as a server-to-server asynchronous messaging / pubsub protocol to help us with distributed processing and long running transactions. But I am already stretching my knowledge in this area and would love to chat with others who are thinking of using XMPP as a server-to-server protocol. Julien - can I pick your brain?

Ick. Do not pass go. Do not collect $200.

For server-to-server passing, prefer (in order):

   1. redis pubsub
   2. zeromq (if you know what you're doing)
   3. amqp (if you think you need it)
   4. populate events to a DB transactionally then consume later

Only use XMPP if your problem domain is "someone is paying me $LOTS to set up an XMPP service."

I'd like to understand more about this and your thoughts. Have you had experience using XMPP this way? Is there a specific reason why this wouldn't / shouldn't work? I know you prefer the other approaches, but other than simply preferring them, what is the issue with using XMPP this way?

Specifically, what if the scenario is enabling communication between servers that you have limited control over and do not have shell / root access to install or manage a server? In this case, there wouldn't be an opportunity to install redis, 0mq, or amqp. The database approach might work, but the servers are distributed and might not allow remote connections. Why wouldn't XMPP work in this scenario using a public XMPP server?

I'd like to learn more!

First, XMPP obviously works. Google Chat is XMPP. Facebook Chat is XMPP (ejabberd). But SOAP works too. Doesn't mean I want to use it.

My problem with XMPP is best illustrated by XEP-0060, the pubsub extension proposal: http://xmpp.org/extensions/xep-0060.html -- I don't have time to figure out that monstrosity.

AMQP is at the limit of complexity as far as pubsub things go. It's complex enough to need explaining, but simple enough were you can understand it in an hour.

If you want an in-depth discussion war about pros and cons, ask your question both on the redis mailing list and on the rabbitmq mailing list. I'd be interested in seeing how both communities respond to your requirement of running on limited access servers.

Thanks for the response! Ok, so to summarize, XMPP works, but in your opinion, it's simply too complex to "figure out"? Basically, in my scenario, it could very well work as optimally as we want it to if we give ourselves time to understand it?

I wish I could use zeromq or redis or amqp, but it just is not an option in this environment.

I was wondering if there was some solid technical reason to not use XMPP, but it looks like there isn't one... it's just a matter of personal preference and wanting to avoid spending time on something. I'll charge ahead with the XMPP implementation in our scenario unless there's a good reason someone can see why not to.

Twitter had an XMPP feed at one point, but shut it down due to scaling issues and later brought up their current firehose/sitestreams service. Does anyone know if they ever talked about why XMPP didn't scale for them?

Site streams requires making one connection per 100 users; perhaps they were having trouble sharding with XMPP?

I think they were mostly having issues because people would enter their gtalk jid to get content... and google obviously throttles the traffic pretty aggressively, so dev would not receive the content and would complain.

Happy to help. catch me on julien@superfeedr.com

Tnx! Just sent you a message.

Do you have any resources as to what XMPP actually is? I've only seen it mentioned in the chat protocol context.

http://xmpp.org/

I've been using ejabberd a lot lately and it's a really nice piece of software, and works very well.

My biggest problem with XMPP as a whole is... well, it's XML. Not only is it heavier than it should be across the wire, it feels to me that the XML way of thinking leads to unnecessary verbosity when designing protocol messages. And there seems to be no proper consensus on how to use it among the different XMPP RFCs -- do we re-use a node name or come up with something different? Or just make it an attribute? Do we namespace it?

XMPP works great for what it was designed for though. There are many robust client and server implementations, being able to federate is awesome, and it's pretty easy to extend. But if I were to re-invent it, I would use a binary transport format.

If you don't want the pain of setting up ejabberd, Prodosy has http://code.google.com/p/prosody-modules/wiki/mod_websocket module already... And is much nicer to setup.

Unfortunately this is not yet a usable solution. I'd love to see this implementation ported to Prosody though.

Very cool! Unfortunately, most browsers are disabling websockets due to security issues in the websocket protocol itself.

https://developer.mozilla.org/en/WebSockets

Can't wait until they fix this!

We're quite hopeful that this will indeed be fixed very soon!

This is really great news. Having identity, presence and all the XMPP goodness delivered to the browser will be great!

By any means I'll stand on a point that using pure XMPP from a JS point of view is a total over utilization. XMPP is perfect when you're able to make it fit your needs and (more important) you are able to hide it's extreme complexity from your user.

I wonder if it would at all be possible to do the reverse - do html over xmpp?

With the advantages xmpp may or may not have over http/html, this could be interesting.

XMPP can carry anything, but it can more easily carry XML-based formats like XHTML. But given that, yes. Formatted IM messages are already specified as a subset of XHTML and you can trivially create your own messages that do whatever custom thing you want with XHTML on your page, or float your custom addition on top of existing messages as a namespaced addition.

The most interesting obvious usecase to me would be using XMPP and ejabberd as a message backplane for your website, hanging various components off of ejabberd that can integrate with your web connection.

> using XMPP and ejabberd as a message backplane for your website

Why not 0mq and json ? Something like Mongrel2 perhaps?

Because then you'd have to implement your own presence, discovery, and routing mechanisms. You get all of that (and more) for free with an XMPP backplane like ejabberd. Even if you decide it's better to roll your own, you'll then have to come up with a consistency and clustering model in order to scale it.

Very cool! I might switch from OpenFire to ejabbered just to use this if it continues to mature.

We will keep working on this as we will obviously use it ourselves :)

I'd argue that ejabberd is faaar more mature than OpenFire. Their web gui is a little less polished but last I checked OpenFire's clustering mechanism is "buy very expensive oracle database". Still for small (under 100 users) installations without uptime guarantees OpenFire is easier to set up.

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