What you could do is tail -f mod_jk.log file. Then take down the tomcat, see if 
the errors appear. You should see something like the following.

Good Entries to Track

Attempting to map context URI '/search-engine*'
ajp_unmarshal_response::jk_ajp_common.c (621): status = 302
 
Maintaining worker loadbalancer1
Maintaining worker prod_se1
Maintaining worker prod_se2

Maintaining worker prod_sea
Maintaining worker prod_seb

service::jk_lb_worker.c (612): service worker=prod_sea jvm_route=prod_sea
service::jk_lb_worker.c (612): service worker=prod_seb jvm_route=prod_seb
service::jk_lb_worker.c (612): service worker=prod_sea jvm_route=prod_se1
service::jk_lb_worker.c (612): service worker=prod_seb jvm_route=prod_se2

Possible Error Entries

Error connecting to tomcat. Tomcat is probably not started or is listening on 
the wrong port. worker=prod_se1 failed
Error connecting to tomcat. Tomcat is probably not started or is listening on 
the wrong port. worker=prod_se2 failed

You should be able to trace where your config is problematic.

Kind regards / Met vriendelijke groet,
Lawrence Lamprecht

-----Original Message-----
From: Matthew Laird [mailto:lai...@sfu.ca] 
Sent: Tuesday, June 02, 2009 8:53 PM
To: Tomcat Users List
Subject: Re: jk Status not showing errors

Unfortunately I'm not seeing that.  What I did was start both Tomcats in 
my LB pair, start Apache, then I take the second Tomcat down to see if 
it will detect it being failed.

Unfortunately it never seems to, it just shows the second as OK/IDLE, 
and happily directs all requests to the first.  This concerns me, 
because if the second were to fail, then later the first, everything 
would die and I'd have no advance warning.  I can't seem to make it ping 
and detect a dead Tomcat.

I am using the latest version of mod_jk, I upgraded that before I began 
playing with the load balancer settings.  I'd appreciate any feedback on 
what I might be doing wrong.  Thanks.

workers.properties:

worker.list=production,development,old,jkstatus

worker.production.type=lb
worker.production.balance_workers=production1,production2
worker.production.sticky_session=True
worker.production.method=S

worker.lbbasic.type=ajp13
worker.lbbasic.connect_timeout=10000
worker.lbbasic.recovery_options=7
worker.lbbasic.socket_keepalive=1
worker.lbbasic.socket_timeout=60
worker.lbbasic.ping_mode=CI

worker.production1.reference=worker.lbbasic
worker.production1.port=8009
worker.production1.host=localhost

worker.production2.reference=worker.lbbasic
worker.production2.port=8012
worker.production2.host=localhost

worker.development.port=8010
worker.development.host=localhost
worker.development.type=ajp13

worker.old.port=8011
worker.old.host=localhost
worker.old.type=ajp13

worker.jkstatus.type=status


Lawrence Lamprecht wrote:
> I do not know if this is relevant or not, but I have just installed the 
> latest version of mod_jk and the jkstatus is very much better than it used to 
> be.
> 
> I had the same issue with loadbalancers not showing when they are offline or 
> broken. With the latest version, jksataus has the possibility to auto refresh 
> itself. This now shouws when load balancers go down without a request being 
> send to it. It is pretty dynamic as well. I ran several tests where I took 
> one of the balancers down, and left jkstatus refreshing every 10 seconds and 
> that told me that the worker was in error.
> 
> It also shows you that the work is OK - IDLE when the worker is not being 
> used but is good. As soon as it receives a request the status then changes to 
> OK.
> 
> Hope this helps.
> 
> Kind regards / Met vriendelijke groet,
> Lawrence Lamprecht
> Application Content Manager
> QUADREM Netherlands B.V.
> Kabelweg 61, 1014 BA  Amsterdam
> Post Office Box 20672, 1001 NR  Amsterdam
> Office: +31 20 880 41 16
> Mobile: +31 6 13 14 26 31
> Fax: +31 20 880 41 02
> 
> 
> 
> Read our blog: Intelligent Supply Management - Your advantage
> 
> 
> -----Original Message-----
> From: Rainer Jung [mailto:rainer.j...@kippdata.de] 
> Sent: Saturday, May 30, 2009 2:46 PM
> To: Tomcat Users List
> Subject: Re: jk Status not showing errors
> 
> On 29.05.2009 22:50, Matthew Laird wrote:
>> Good afternoon,
>>
>> I've been trying to get the jkstatus component of mod_jk running, and
>> I'm not quite sure what I'm doing wrong in trying to have it report dead
>> Tomcat instances.
>>
>> I have two tomcat instances setup in a load balancer, as a test I've
>> taken down one of them.  However the jkstatus screen still shows both of
>> them as OK.  I'm not sure what I'm missing from my workers.properties
>> file to make it test the Tomcat and report a failed instance, so I can
>> set Nagios to monitor this page and report problems.
>>
>> My workers.properties is:
>>
>> worker.list=production,development,old,jkstatus
>>
>> worker.production.type=lb
>> worker.production.balance_workers=production1,production2
>> worker.production.sticky_session=True
>> worker.production.method=S
>>
>> worker.lbbasic.type=ajp13
>> worker.lbbasic.connect_timeout=10000
>> worker.lbbasic.recovery_options=7
>> worker.lbbasic.socket_keepalive=1
>> worker.lbbasic.socket_timeout=60
>>
>> worker.production1.reference=worker.lbbasic
>> worker.production1.port=8009
>> worker.production1.host=localhost
>> #worker.production1.redirect=production2
>>
>> worker.production2.reference=worker.lbbasic
>> worker.production2.port=8012
>> worker.production2.host=localhost
>> #worker.production2.activation=disabled
>>
>> worker.development.port=8010
>> worker.development.host=localhost
>> worker.development.type=ajp13
>>
>> worker.old.port=8011
>> worker.old.host=localhost
>> worker.old.type=ajp13
>>
>> worker.jkstatus.type=status
>>
>>
>> Any advice on extra options to make jkstatus check and report when one
>> of the Tomcat instances isn't responding would be appreciated.
> 
> I assume, that the actual error detection works and you are really only
> asking about display in status worker. I also assume your are using a
> recent mod_jk. Nevertheless do yourself a favor and look at the Timeouts
> documentation page to improve your configuration.
> 
> Until recently, only workers used via a load balancing worker had good
> manageability with jkstatus. Very recently also pure AJP workers without
> any load balancer got more useful information in their display.
> 
> So let's talk about your worker "production". Whenever a request comes
> in the lb first checks whether it already carries a session for one of
> the nodes 1 or 2, or whether the request can be freely balanced.
> 
> The status of a worker (node) in jkstatus can only change, if a request
> is been sent to the worker. So if all your requests belong say to node
> 2, you'll never notice anything is wrong with 1. But if 1 is broken, and
> a request for one comes in, or a request that is freely balanceable and
> the lb decides to send it to 1, then JK will detect the problem and
> display it. The display will switch from "OK" to "ERR".
> 
> If you want to parse the info, do not choose the html format, instead
> choose a different output format, like XML or the properties format
> (line oriented).
> 
> Regards,
> 
> Rainer
> 
> 
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-- 
Matthew Laird
Lead Software Developer, Bioinformatics
Brinkman Laboratory, MBB Dept.
Simon Fraser University

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