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From 张文东 <zwd2...@gmail.com>
Subject Re: [users@httpd] (mod_jk load balancer) could not get free endpoint for worker xxx
Date Wed, 25 Mar 2009 08:44:15 GMT
Hi André Warnier,

I modified the ajp connection configuation in wasce, such as ajp
maxthreads, but it seems that it's not the reason for the "could not
get free endpoint for worker" error.

I set a series pool size and test the differences between them. (one node case)
pool_size	errors
25-50	5927
50-100	275
80-160	828
100-200	2
100-200 	45
80-160 	132

the test results show that the performance turns to be better when
pool_size increase. but when I add 2 nodes, the pool_size if 80~160
for each one (160~320 total) the httpd server occurs many 503 errors.

I think maybe the httpd server could not hold so many pool size
(cache?). I want to increase the httpd's ThreadsPerChild. but I found
it cannot set larger than 400 (this ThreadLimit is seted too). when
>400, the httpd error_log output:  "[alert] (12)Cannot allocate
memory: apr_thread_create: unable to create worker thread".

btw, I'm using IBM HTTP SERVER 7 (whose kernal is based on
apache.2.2). And the Machine for httpd server is PPC (4cpus & 32G
RAM), the usage for httpd server is very low.

I'm trying to fix this problem, and further progress I will post to
you all. thanks for concern about this.


2009/3/24 André Warnier <aw@ice-sa.com>:
> 张文东 wrote:
>>
>> Hi all.
>>
>> I'm using httpd 2.2 and websphere application community edition
>> (wasce) 2.1.1 (you may treat it as tomcat if you are not familiar with
>> wasce).
>> My goal is: the httpd server delivers 3000 requests per second to the
>> wasce servers. I use the mod_jk module, and the workers.properties
>> conf like this:
>>
>> ...
>> worker.node5.port=8009
>> worker.node5.host=9.186.96.71
>> worker.node5.type=ajp13
>> worker.node5.connection_pool_size=50
>> worker.node5.connection_pool_minsize=25
>> worker.node5.connection_pool_timeout=600
>> worker.node5.lbfactor=1
>>
>> worker.loadbalancer.type=lb
>> worker.loadbalancer.balance_workers=node1, node2,node3,node4,node5
>> worker.loadbalancer.sticky_session=1
>> worker.loadbalancer.sticky_session_force=0
>>
>> now the question is, I'm using mod_jk as the load balancer server.
>> when users' requests increase (more than 1000requests per second),
>> there are many warnings in the mod_jk.log:
>> [Tue Mar 24 15:36:37 2009] [14425:735282400] [warn]
>> ajp_get_endpoint::jk_ajp_common.c (2946): Unable to get the free
>> endpoint for worker node3 from 50 slots
>> [Tue Mar 24 15:36:37 2009] [14425:4059268320] [info]
>> service::jk_lb_worker.c (1161): could not get free endpoint for worker
>> node3 (0 retries)
>>
>> and the performance of httpd reduce.
>>
>> I want to know is there anybody having the SAME SITUATION or someone
>> knows is there any error in my worker.properties configuation (which
>> causes the could not get free endpoing error).
>>
> Not the ultimate specialist here, but what is the configuration of your
> back-end Connectors ?  I mean, what it sounds like to me from the error
> messages above, is that the worker is just not able to connect to a free
> thread at the back-end level, meaning that the back-end nodes are saturated,
> not your front-end mod_jk.
>
>
>
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>



-- 
Best Regards!
Wen Dong

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