How does Gmail do comet on Opera?

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+7 Q:

How does Gmail do comet on Opera?

I would like to know how Gmail (or anyone else) does comet on Opera.

Here is what I know so far from my experiments.

It doesn't use the event-source tag which is broken in Opera 10.51.
It doesn't use iframe which displays a spinning throbber and a busy mouse cursor.
It doesn't use responseText on xmlhttprequest when readyState = 3 which is known to be broken on Opera.

I tried seeing how it was done in mibbit and etherpad, and I found that they both use long-polling.

Bounty

The bounty goes to whoever can tell me a method better than "event-source" for Opera comet streaming, or how gmail does streaming (or long-polling if it does that).

I really don't have any idea on what the answer is. But I know Opera supports server-events : http://my.opera.com/WebApplications/blog/show.dml/438711 . Maybe it's a step towards the anwser? I'm not really sure either, but I think they use it within Opera Unite.

Savageman 2010-04-17 22:59:31

No, it doesn't use event-source like I said. Event-source is completely broken in Opera 10.51, and gmail still streams gchat just fine.

Unknown 2010-04-18 00:54:08

+6 A:

GMail uses BrowserChannel (Docs | Source), which is included in Google's Closure Library.

@fileoverview Definition of the BrowserChannel class. A BrowserChannel

simulates a bidirectional socket over HTTP. It is the basis of the

Gmail Chat IM connections to the server.

Jason Hall 2010-04-19 06:52:57

i.e. http://closure-library.googlecode.com/svn/docs/closure_goog_net_browserchannel.js.htmlThink what you're actually looking for is around here:http://closure-library.googlecode.com/svn/docs/closure_goog_net_channelrequest.js.source.htmlsearch for pollResponse_ and getNextChunk_ :)

hallvors 2010-04-19 13:40:58

Can you be a little more specific? I feel that I've given a generous enough bounty to warrant an answer more than just a link to a giant abstract library.

Unknown 2010-04-19 22:26:51

Well, I sort of feel that should be left to Jason as he gave the original pointer to Closure and I just went a little bit deeper.. Looking at that source code, it seems to use an async XMLHttpRequest indeed, with a timeout that's responsible for polling the responseText and handle incoming data. Opera doesn't fire several readystatechange events while chunked data is coming in (which Firefox does mostly by a happy accident I think - there is no standard or documentation mandating this implementation as far as I know). So instead of expecting multiple readystatechange events they use timeouts.

hallvors 2010-04-20 13:56:18

@hallvors, yes I was addressing Jason. If you leave a more detailed answer I will accept yours unless you feel that Jason deserves the bounty.

Unknown 2010-04-21 21:52:43

Unfortunately the documentation on BrowserChannel is pretty thin, and I don't have any first-hand experience with it myself, so I can't really say how it solves this particular problem. The best you can do is look at the code and try to work it out. If you don't think I deserve the bounty, I'm fine with that, I was just trying to point you in a helpful direction.

Jason Hall 2010-04-21 21:55:00

There's a sidebar question which seems like it may also be helpful? http://stackoverflow.com/questions/2481696/how-does-gmail-implement-comet

Jason Hall 2010-04-21 22:07:20

@Jason, I will give you the bounty if your remains the best answer. But if you can improve it some more, I will give you the bounty right away.

Unknown 2010-04-21 23:48:24

I think that rather cross-browser (including Opera) approach might be to stream data through an Adobe Flash application. Though it would introduce dependence on the Flash plugin and is not very popular because of that.

newtover 2010-04-25 12:59:53

ansaurus

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How does Gmail do comet on Opera?

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