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From Rainer Jung <>
Subject Re: 503 under load
Date Wed, 07 May 2008 21:53:24 GMT
Hi David, schrieb:
> Hi,
> We've started to stress test a new website, and are seeing 503's 
> interspersed when we are under load.  We are running Apache - Tomcat 
> combination.
> Could someone give me an idea of what can cause this, and where to start 
> looking?

I expect the 503 is generated by httpd/mod_jk. If so, then your mod_jk 
log file should give an idea, if httpd couldn't contact Tomcat, didn't 
get an answer, ...

Is your stress test using a defined maximum parallelity? If not and your 
test client uses a timeout, then once your app gets slow, you'll easily 
saturate all Tomcat threads, DB connections, ... and finally httpd will 
no longer be able to send new requests to Tomcat.

Du regular thread dumps to your Tomcat while being under stress, to 
check what the AJP threads (TP-Processor) are actually doing.

> cheers,
> David



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