I am working on a solution that has a very high number of users and a 
significant amount of traffic.  Using a zeo configuration we have been running 
into a few bottle necks while trying to improve our load testing results.  The 
problem we see is if that put our Zeo Configuration under load that Zope does 
not close the connections and the application server ends up running out of 
connections for Apache to connect to.  The connections once opened idle 
indefinitely.  (Apache is running on a dedicated server different from our Zeo 
instances).  We are using RR between 2 vm instances using 10 zeo clients per vm 
to distribute load.  The bottleneck is occurring on the Apache server because 
it's keeping TCP connections in time_wait status.

We have completed load tests on both Windows 2003 and 2008.  In 2003 we were 
able to adjust the registry so the OS would terminate connections after 15 
seconds of idle, however in 2008 the minimum is 30 seconds.  In the upper 
levels of testing the OS runs out of TCP connections because it can't close 
them fast enough and it begins to fail requests.  Ideally we don't want to 
close connections forcibly via the tcp stack because Zope keeps them open.  
We'd hope that Zope would manage this clean up gracefully.

One option we are considering is using IIS7.5 and ARR as a replacement load 
balancing/rewrite method.  This could allow us to check health of destinations 
prior to forwarding a request.  It may also give us more control over closing 
connections at the OS level.

One other detail we think might be the issue is that Zope is not initiating the 
close connection event.

Does anyone have any experience or knowledge they can lend to help out?

Windows 2003/2008 server
Apache 2.1
Zope 2.12
MS SQL 2005
Python 2.6.6
SQLAlchemy 0.6.5
sqlalchemy version is 0.6.5
and z3c.sqlalchemy=1.4.0

Jimmy Small (mallaice)

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