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From Scott McClanahan <>
Subject Re: mod_jk error detection
Date Wed, 25 Jul 2007 17:00:26 GMT
On Wed, 2007-07-25 at 17:00 +0200, Rainer Jung wrote:
> Hi,
> good questions. First of all: I just today wrote a new docs page about 
> timeouts. We are soon releasing 1.2.24 which contains this page. You can 
> already look at it under
> (The new page is named "Timeouts" and part of the group Generic Howtos.
> Also the new docs contain a better explanation, what retries means, 
> especially the huge difference between retries for an lb worker and a 
> usual worker. This info is on the updated page in the 
> reference guide.
> > With these settings how could I expect the connector to behave if:
> > 
> > 1.  Tomcat dies and the port is no longer listening resulting in an
> > immediate icmp response.
> I would expect, that any attempt to use an existing connection or to 
> open a new one immediately returns with an error, because the remote 
> machine rejects the communication. Further JK behaviour is now depending 
> if you are using a load balancer or not. Se retries etc. in the updated 
> docs.
> > 2.  The box hosting tomcat dies or the tcp stack for whatever reason
> > tanks resulting in no immediate icmp response.
> As long as your local system or the last router still has an arp entry 
> for the died machine, you will run into very long TCP timeouts. We 
> recommend CPing/CPong, see the new Timeouts page.
> > 3.  The connector does make a successful connection to the backend
> > tomcat worker only to have that worker become slow and almost
> > unresponsive.
> You should use CPing/CPong and reply timeouts. See again the new 
> Timeouts page. If you don't use an lb, the best you can do is throwing 
> an error early, such that the rest of the infrastructure doesnt get 
> congested.
> > Are there more directives I should be concerned with?  Currently, I have
> > no intentions on monitoring the http response status codes to detect
> > errors.
> Look at the new page and look at the page of the 
> reference guide. Use a load balancing worker, set recovery_options etc.
> HTH.
> Regards,
> Rainer
> P.S.: If you have suggestions how to improve the new page: it's not 
> public yet. If you are fast enough, we can include those changes.
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Thanks I'll be reading up this afternoon and posting comments.

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