[Spread-users] Strange ordering problem

Melissa Jenkins melissa-spread at temeletry.co.uk
Tue Oct 5 15:30:29 EDT 2010


Just wondering if somebody could point me in the right direction on this...

I've got a setup with two Spread servers in a single broadcast segment.

I have a writer on the first server, and a process on each of the second servers that listen for messages and process them.

What I've noticed is that although I'm using AGREED_MESS the reader on the second normally gets the messages out of order, and the one on the first occasionally gets them out of order. (I started with FIFO_MESS as I only have one source, but both seem to behave the same way.)

This only happens under very high load - and seems to happen in 'chunks', where a series of messages is delivered out of order (possibly in reverse if one run is indicative) and then normal ordering returns.

I'm using Spread 4.1.0, and Spread-3.17.4.4 perl module.

There doesn't appear to be any change in membership during this process.  The two machines are connected to the same switch and the port is not overloaded.  
The readers are not being kicked off and are keeping up with the messages.  The writer has a queue to send to Spread which seems to back up a little, though messages are not stuck for a measurable period of time.

The traffic appears to burst in a similar fashion - every now and then it just pauses - though I'm not sure that is related.

I'm at a bit of a loss as to what to look at - all suggestions of where to start would be hugely gratefully received!

Thanks,
Mel



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