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From Rainer Jung <>
Subject Re: mod_jk error detection
Date Wed, 25 Jul 2007 15:00:00 GMT

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 

> 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 

> 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.




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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