[whatwg] [Server-Sent Events] Infinite reconnection clarification

Odin Hørthe Omdal odinho at opera.com
Fri Apr 27 04:12:55 PDT 2012

I think I should do a TLDR since I didn't really get any answers:

1. Should EventSource *ever* time out once it has once been connected?
2. What do browsers do today? What do you think is a good thing to do?

I tried Opera, Firefox and Chromium for question 2.

Opera: Gives up after 2-3 minutes.
Firefox: Gives up after ~15 minutes.
Chromium: Doesn't ever give up. Longer and longer retry intervals, upper  
limit (I think) of 1 minute between each retry.

And the TL version follows:

On Tue, 17 Apr 2012 16:44:56 +0200, Odin Hørthe Omdal <odinho at opera.com>  

> If I understand correcly, the spec expects the implementation to keep
> reconnecting indefinitely, when the network cable is yanked. It is a
> strong feeling, but it'd be nice to get it clarified in plain text in the
> spec.
>> Clients will reconnect if the connection is closed; a client can be  
>> told to stop reconnecting using the HTTP 204 No Content response code.
>> CLOSED (numeric value 2)
>> The connection is not open, and the user agent is not trying to  
>> reconnect. Either there was a fatal error or the close() method was  
>> invoked.
>> The task that the networking task source places on the task queue once  
>> the fetching algorithm for such a resource (with the correct MIME type)  
>> has completed must cause the user agent to asynchronously reestablish  
>> the connection. This applies whether the connection is closed  
>> gracefully or unexpectedly. It doesn't apply for the error conditions  
>> listed below.
> And this is the place a small clarification could come in handy:
>> Any other HTTP response code not listed here, and any network error  
>> that prevents the HTTP connection from being established in the first  
>> place (e.g. DNS errors), must cause the user agent to fail the  
>> connection.
> Maybe "Network errors after a successfully established connection must
> cause the user agent to try reestablishing the connection indefinitely."
> Or something better. At least, make it clear what is going to happen. :-)
> On that note, it'd also be nice to hear what the other vendors do with  
> the
> connection. It seems like both Firefox and Chromium has an exponential
> fallback with a max-value between the reconnection tries. The first tries
> will probably respect the given *reconnection time*, but after a while
> that'll be too often.
> I tried yanking the network for 10+ minutes, and when I put the cable in
> again, both Firefox and Chromium used 25 seconds to reconnect. When only
> yanking it for one minute, the reconnection was much faster (2-5  
> seconds).
> This with *reconnection time* set to 500ms.

Odin Hørthe Omdal (Velmont/odinho) · Core, Opera Software, http://opera.com

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