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From Arica <xun...@263.net>
Subject Re: High CPU usage impact to log4j
Date Wed, 24 Jun 2009 08:25:15 GMT

Hi, all

Please just ignore what I have said.

I've retested the case again, the log4j did output logs even the resided JVM
took more than 95% CPU. (I use infinite loop to make the JVM to takes most
CPU of the OS)  In fact, our application deploys total 7 JVMs. When the
issue reported by our customer, I found that one of 7 JVMs took more than
90% CPU. After checking all debug logs, only the JVM with more than 90% CPU
usage did not have any logs output...the other 6 worked well...the overal OS
CPU idle is 0...that's why I suspected at the very begining that the high
CPU usage is the root cause to make log4j not work.

Rignt now, I'm wondering...that why my own simulation cannot reproduce the
issue? It seems that the high CPU usage of JVM is not the real root cause of
the problem...so...do you have any hints about the "not log output" issue of

I'm quite frustrated...

Any suggestions or tips would be appreciated.

Arica wrote:
> Hi, buddies
> I deployed the log4j as the logging tool of my JVM. Recently, I found that
> the log4j does not work, I could not find any log output when the JVM
> encountered the high CPU usage issue. In the case, the JVM took more than
> 90% CPU usage. I really want to know that my JVM is doing...I know I can
> do it through JVM thread dump. But the question is why log4j does not
> output any logs? I cannot find any warning from the guild to state that
> log4j will lose logs during the CPU penic.
> Do you have any idea about that? Or does log4j define any threshold of CPU
> usage?
> Thanks.

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