jetty-support

[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

Re: [Jetty-support] Annoying problem in Jetty 5

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

Please ignore this, I've checked a bit further and it looks like the
code was incorrectly calling start() on the listener before setting the
maxThreads parameter.

Regards
Rob Stone

On Thu, 2009-12-17 at 18:49 +0000, Robert Stone wrote:
> 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
> 
> 
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Robert Stone 
Systems Consultant
Rostrvm Solutions Ltd 
  
www.rostrvm.com 
  
  
T:  + 44 (0) 1483 744431
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