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From Taylan Develioglu <tdevelio...@ebuddy.com>
Subject Re: CPU usage with APR and connectionTimeout impact
Date Thu, 02 Apr 2009 11:59:43 GMT
Funny,

according to the documentation there exists no connectionTimeout
attribute for the apr connector.

Setting the value to '0' could mean all sorts of behavior, no way to
know for sure short of  checking the code. (it could mean the connector
will not wait for the uri line at all)

I  can't comment about a correct value for your application.

Setting it to a low value will  have the connector thread return to the
pool faster on connections where the peer has gone to lunch after the
initial connection. This only matters if you have a large number of such
peers.

I'm sure one of the veterans here can clear this up for you.
>
> Hello,
>
> In my project, we are using Tomcat 6.0.18, with APR 1.2.12 and tc
> native 1.1.14 on an Redhat OS (Linux kernel 2.6.18).
> There is a behavior that I can't explain:
>
> -with connectionTimeout="0", the process tomcat uses a huge percentage
> of CPU, even if there is no traffic.
> but we doesn't observe any problem and the response time is good.
>
> -with connectionTimeout="5000", the process tomcat uses a normal
> percentage of CPU, when there is no traffic.
>
> -without APR and with connectionTimeout="0", the process tomcat uses a
> normal percentage of CPU when there is no traffic.
>
> After different searches on the web, tomcat manual and mailing lists, I
> don't find the reason of the link between CPU usage and
> connectionTimeout/keepAliveTimeout with APR.
> With the previous release of Tomcat (5.5) and APR, we have a similar CPU
> usage (without traffic, high CPU load) and when we modify another
> parameter ("firstReadTimeout"), the behavior also changes in the same
> way.
>
> I know there is no real trouble, but I'm curious and prudent: I don't
> like to do something, when I don't understand what is hidden behind.
> Could somebody explain to me why Tomcat/APR has these behaviors?
> Is there a performance risk to set connectionTimeout to 5000?
>
> Thank you for your answers.
> Yann
>
>
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