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Posted to users@tomcat.apache.org by Taylan Develioglu <td...@ebuddy.com> on 2009/04/02 13:59:43 UTC
Re: CPU usage with APR and connectionTimeout impact
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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Re: CPU usage with APR and connectionTimeout impact
Posted by yann grostete <ya...@alcatel-lucent.fr>.
Hello,
The parameters connectionTimeout and keepAliveTimeout are not on the APR
side. They are attributes of AJP and HTTP connectors.
Setting the value to 0 means no timeout (according to some mail exchange
I found in tomcat mailing list).
No timeout is default value of this attribute.
My question is also: why a connector attribute has a so subtential
impact on tomcat cpu usage, when APR is used?
And for the peers going to lunch after the initial connection, it's
true: we have a large number of such peers.
Thank you for your help. And the help of "one of the veterans" will be
very appreciated.
Regards
Taylan Develioglu a écrit :
> 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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>> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
>> For additional commands, e-mail: users-help@tomcat.apache.org
>>
>>
>
>
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RE: CPU usage with APR and connectionTimeout impact
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: Taylan Develioglu [mailto:tdevelioglu@ebuddy.com]
> Subject: Re: CPU usage with APR and connectionTimeout impact
>
> I think a seperate overview of attributes per connector would be
> clearer.
Strongly agree with that. Patches?
> The HTTP connectionTimeout description states:
>
> - The number of milliseconds this *Connector* will wait, after
> accepting a connection, for the request URI line to be presented.
> The default value is 60000 (i.e. 60 seconds).
>
> '0' is not explicitly defined as a special value.
For the Java connectors, the connectionTimeout value is used in Socket.setSoTimeout(), where the API doc states "A timeout of zero is interpreted as an infinite timeout." Looks like the APR implementation may well interpret zero somewhat differently, resulting in a CPU overheating test...
- Chuck
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Re: CPU usage with APR and connectionTimeout impact
Posted by Gregor Schneider <rc...@googlemail.com>.
On Thu, Apr 2, 2009 at 3:37 PM, Taylan Develioglu
<td...@ebuddy.com> wrote:
>
> I think a seperate overview of attributes per connector would be clearer.
>
+1
Somebody got some time to change it in the TC trunk and cis able to
reate a bugzilla-RFE with a patch?
Any volunteers welcome ;)
Rgds
Gregor
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Re: CPU usage with APR and connectionTimeout impact
Posted by Taylan Develioglu <td...@ebuddy.com>.
You're right. I missed it. APR has the same attributes as the HTTP
connector.
I think a seperate overview of attributes per connector would be clearer.
The HTTP connectionTimeout description states:
- The number of milliseconds this *Connector* will wait, after accepting
a connection, for the request URI line to be presented. The default
value is 60000 (i.e. 60 seconds).
'0' is not explicitly defined as a special value. According to the
description it would mean a wait period of 0 milliseconds for the uri to
be presented. This would make the connector practically useless.
Caldarale, Charles R wrote:
>> From: Taylan Develioglu [mailto:tdevelioglu@ebuddy.com]
>> Subject: Re: CPU usage with APR and connectionTimeout impact
>>
>> according to the documentation there exists no connectionTimeout
>> attribute for the apr connector.
>>
>
> Which documentation is that? Note that the HTTP connector attributes apply when running in APR mode. Quoting from the APR-specific doc:
>
> "The following attributes are supported in the HTTP APR connector in addition to the ones supported in the regular HTTP connector:"
>
> What's not clear in the doc is that many of the HTTP attributes also apply to the NIO version of the protocol handler.
>
> - Chuck
>
>
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RE: CPU usage with APR and connectionTimeout impact
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: Taylan Develioglu [mailto:tdevelioglu@ebuddy.com]
> Subject: Re: CPU usage with APR and connectionTimeout impact
>
> according to the documentation there exists no connectionTimeout
> attribute for the apr connector.
Which documentation is that? Note that the HTTP connector attributes apply when running in APR mode. Quoting from the APR-specific doc:
"The following attributes are supported in the HTTP APR connector in addition to the ones supported in the regular HTTP connector:"
What's not clear in the doc is that many of the HTTP attributes also apply to the NIO version of the protocol handler.
- Chuck
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