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From br1 <myrealbr...@myrealbox.com>
Subject Re: JK and IIS - troubles?
Date Thu, 02 Oct 2008 20:43:50 GMT

Rainer,


Rainer Jung-3 wrote:
> 
> That might be the reason for trouble. If things start to get slow, the 
> web server gets filled by all thenew requests still coming in without 
> answering fast enough the existing ones. 
> 
This starts to make sense now. 
I have a few suggestions inline, I would like to contribute to document a
case like this, if possible. 


Rainer Jung-3 wrote:
>  People often try to work around 
> this by increasing the number of threads available for processing the 
> requests, 
> 
Yes, some of us might still be used to old JK connectors defaulting to 10
connections.
More likely to cause confusion is the Tomcat message "increase the threads",
while it might help more if it was "fine tune the threads" instead.  


Rainer Jung-3 wrote:
> 
> but if the backend is stuck or too slow, this will not help 
> and instead also trash the frontend.
> 
So perhaps.. upgrading from older JKs the default changed from 10
connections to 250. With a lot of workers (for instance, 40) the total
number of maximum threads went from 400 to 10000. I will have to fix this
and check what happens.

Though I understand the perfect default value can vary depending on the site
load etc., to me 10 is too low and 250 is far too high.. maybe a 50 would
fit for most installations and be a better default number in this case. :-)


Rainer Jung-3 wrote:
> 
> You should measure how many connections you need during peak hours 
> without performance problems, and then add some percentage depending on 
> your growth rate etc. Finally you need to make sure, that your web 
> server itself uses at least as many threads, as you configured as the 
> pool size.
> 
This has been measured already. Same as above, when the problem were too few
connections, too many seemed not to be a problem. :-)
I would suggest to add your above sentence right after "We recommend
adjusting this value for IIS and the Sun Web Server" at
http://tomcat.apache.org/connectors-doc/generic_howto/timeouts.html and
maybe also in http://tomcat.apache.org/connectors-doc/reference/workers.html
(And maybe *strongly* recommend it )


Rainer Jung-3 wrote:
> 
> For Apache with mod_jk we can automatically detect the number of threads 
> and by default size our pool to the same number. For IIS you have to 
> size the pool yourself (or live with the big default of 250).
> 
It seems we are dying with the big default. :-)

I have read somewhere that the number of threads is not likely to cause
these problems on modern multiple cpu with multiple cores servers. I wonder
if there is some kind of formula to know what total should not be exceeded
in this particular case, of if the good old document by Mladen Turk is still
valid fixing this number to 2000
(http://people.apache.org/~mturk/docs/article/ftwai.html)

Thanks a lot for your help,
br1.


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View this message in context: http://www.nabble.com/JK-and-IIS---troubles--tp19750760p19787259.html
Sent from the Tomcat - User mailing list archive at Nabble.com.


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