I'm going through http://www.jboss.org/community/docs/DOC-10217 to help tune 
our jboss server for production.

In the section headed "Tomcat", there is advice about tuning thread parameters 
for the http connector and I'm not sure if I'm understanding this right.

Specifically, I'm looking at minSpareThread and maxSpareThread attributes.

In DOC-10217 it says the following about minSpareThread:

anonymous wrote : You should have minSpareThreads equal just a little more than 
your normal load
and
anonymous wrote : minSpareThreads means "on start up, always keep at least this 
many threads waiting idle"

However, the second quote above doesn't seem to tell the whole story. In the 
Tomcat docs (http://tomcat.apache.org/tomcat-5.5-doc/config/http.html) it says 
the following about minSpareThreads:
anonymous wrote : The number of request processing threads that will be created 
when this Connector is first started. The connector will also make sure it has 
the specified number of idle processing threads available. This attribute 
should be set to a value smaller than that set for maxThreads. The default 
value is 4.

My interpretation of the Tomcat docs description is that this value should be 
set to a figure that equals the usual (or perhaps peak?) thread turnover.  I'm 
not sure that is the same thing as "just a little more than your normal load", 
but maybe that is what the author of the JBoss "slimming" doc meant?

In DOC-10217 it says the following about maxSpareThread:

anonymous wrote : You should have maxSpareThreads equal just a little more than 
your peak load
and
anonymous wrote : maxSpareThreads means "if we ever go above minSpareThreads 
then always keep maxSpareThreads waiting idle"

The Tomcat docs seem to describe maxSpareThreads very differently:

anonymous wrote : The maximum number of unused request processing threads that 
will be allowed to exist until the thread pool starts stopping the unnecessary 
threads. The default value is 50.

Now, I'm not sure exactly what the Tomcat Docs mean by "the unnecessary 
threads" that are being stopped, but my interpretation of this is that once the 
number of unused threads drops below this figure, the server starts hunting for 
other threads that are not yet marked as unused but might be dead or dying.

If that interpretation is correct, then setting this figure to "just a little 
more than your peak load" as suggested in the JBoss slimming document seems to 
me that it would be too high.  I'd have thought this figure would need to be 
set relatively low.  I note that the ratios between the default values 
specified by the Tomcat docs (maxThreads=200, minSpareThreads=4, 
maxSpareThreads=50) don't seem to me to match the recommendations in the JBoss 
Slimming document.

I expect I'm not understanding either document properly, but I'd appreciate 
some discussion on this to clarify things.


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