On Jul 29, 2013, at 5:00 PM, Tristan Seligmann <[email protected]> wrote:
> On Tue, Jul 30, 2013 at 12:31 AM, Glyph <[email protected]> wrote:
>
> On Jul 29, 2013, at 3:10 PM, Werner Thie <[email protected]> wrote:
>
>> I've written a few Nevow/Athena based game servers in the last years, and
>> I'm still convinced that I have chosen the right technology for the problems
>> at hand. Time given, I might tackle the coding to have the underlying
>> transport to be switched to websockets when available as Glyph suggested,
>> but currently I see no performance issues and the servers are running with
>> uptimes now measured in years.
>
> To be honest, the main reason to add websocket support is not so much that
> there is a significant performance problem that needs to be addressed, but
> rather that people are going to show up _expecting_ that there's a
> significant performance problems because they've heard on some JavaScript
> forum that websockets are fast :). If Nevow can just tick that box on the
> feature list, there's that much less to argue about.
>
> I'd like to add that I'm aware of at least one significant performance
> problem[1] in Athena (not sure if there's a bug report lying around for it
> anymore, although I think there was one in Trac-that-was), but it's to do
> with the reliable delivery transport that Athena runs on top of long polling
> (which I believe would still be required on top of websockets), rather than
> the long polling / HTTP itself. Long polling in general is pretty reliable,
> the main problem is with proxy servers that time the connection out faster
> than Athena recycles it, but this value is configurable so the problem is
> easily worked around.
>
> [1] When sending several messages "at once" with Athena under some specific
> set of circumstances (I'm not sure exactly what they are, but the behaviour
> is repeatable), the one side will ACK the first message before processing the
> second message, leading to the other side retransmitting the remaining
> messages even though they were not lost. This shows up as multiple "Athena
> transport duplicate message, discarding: ..." log messages, and has the
> result of increasing bandwidth usage / latency; depending on the number /
> size of the retransmitted messages, the impact may be negligible or
> noticeable.
This does sound like a real bug :). My point is that it's not one that would
necessarily be addressed *just* by switching to websockets...
-g
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