[Twisted-web] Need Help

[Tristan Seligmann]

On Tue, Jul 30, 2013 at 12:31 AM, Glyph <glyph at twistedmatrix.com> wrote:

>
> On Jul 29, 2013, at 3:10 PM, Werner Thie <werner at thieprojects.ch> 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.
-- 
mithrandi, i Ainil en-Balandor, a faer Ambar
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