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From Camille Fournier <cami...@apache.org>
Subject Re: excessive client timeouts tied to NIO select(timeout)
Date Tue, 26 Feb 2013 18:24:21 GMT
Is it possible that something else is going on in the application that is
using this client, or are you observing this happen in a simple test
client? I don't think a 15-25s wait time is within any reasonable bounds of
"more or less". This timeout is passed down to native code in the JVM so a
bug there causing a "more" of that magnitude would probably affect a lot of
people. I would start looking into what kind of networking conditions could
be causing such a hang, assuming you don't have full GC happening that is
pausing the process during this period (which could cause such a long hang).

On Tue, Feb 26, 2013 at 12:15 PM, Brian Tarbox <briantarbox@gmail.com>wrote:

> The main client loop involves sending keep-alive pings in-between calls to
> the NIO selector.select call which looks for data from the server
> (including ping responses).
> What I've found is that the select() which takes a timeout value takes a
> hugely varying time to complete.
> When asking for a max 6 second timeout on the select call I'm in fact
> staying in the call for 15-25 seconds.  Which leads to starving the keep
> alives which leads to timeouts.
> Looking at the NIO documentation of the timeout parameter to select it
> says:
> timeout - If positive, block for up to timeout milliseconds, *more or less*
> *
> *
> Has anyone else seen this or have a suggestion for a work around?  This
> seems like a basic flaw.  If I can't count on timely return from select it
> seems to break the how keep-alive scheme.
> Thanks in advance for any help!
> Brian Tarbox
> --
> http://about.me/BrianTarbox

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