[Jetty-support] Annoying problem in Jetty 5

[Robert S. <rob...@ro...>]

I've just spent the last few days tracking down a problem with one of
our installations. The site is a very high load system with lots (>600)
of very active connections. At times of high load a large number of the
users were getting page refusals (connection resets).

After lots of head scratching I finally found the culprit ! We were
setting the socket listeners maxThreads value to 1000, but after running
a load test in the office I found that I could only make 256 connections
to the server. After this all further connection attempts were refused.

I looked through the Jetty code and found the POOL_MAX variable in
Pool.java, which defaults to 256. Setting this to a higher value (500)
cured the problem. Looking further through the code, it appears that
when you set maxThreads to a higher value this doesn't affect the
_pondLife array which has already been initialised to the lower 256
limit. Now that I know about the problem I can work around it (initialse
POOL_MAX to the same value as we use for maxThreads) but in the absence
of a fix for Jetty 5 it might be helpful to add this to a FAQ somewhere.
I've had a quick look at the Jetty 6 code base (that we use for the
latest version of our software) and can't see anything similar in there.

Regards,
Rob Stone