[Spread-users] strange 2 second hiccups

Kim Barrett kab at irobot.com
Sun Aug 20 20:56:37 EDT 2006

I've been developing an application using spread(4.0.0rc2) and have
run into a very strange performance problem. I have a simple
round-trip test between two machines, and I'm seeing occasional
(perhaps 2%) 2 second round trips, where the vast majority are around
1-2 millisecond. Instrumenting the application led me to suspect that
the 2 second hiccups were occurring within the spread daemon,
although I haven't been able to reproduce the problem with a simple
test case. I modified the application to use bare udp/multicast
rather than spread, as an additional check, and no hiccups occur
there either. Another oddity is that, for any given pair of machines,
the delays always occur in only one direction. All messages are using
UNRELIABLE_MESS. I've spent some time looking over the spread code,
but haven't found anything that would account for this yet. (The bug
report I sent a week or so ago regarding timeout setups was a result
of that examination, but isn't the cause of this problem.) At this
point, I'm pretty much stumped. Any suggestions for how to track this
down would be appreciated.

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