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From Hermes Flying <flyingher...@yahoo.com>
Subject Re: Can not understand how maxThreads of Connectors works
Date Wed, 16 Jan 2013 20:07:28 GMT
Hi Chris, thanks for the reply.
Concerning your questions:
I believe acceptCount can not work with value 0 because if I am not wrong, the acceptCount
is the value passed as backlog in the ServerSocket constructor. According to javadoc if the
backlog value is less than or equal to 0, then a default value is used instead which is 50.
So acceptCount=0 does not mean that backlog queue does not queue anything. That is why I used
the value 1 instead.
Also when I say I was expecting a network failure (bad terminology) I meant that the client
would get a failure in the TCP attempt to connect.
Also I used maxThreads=0 and the server worked fine. Did not see any problem in my applications.
Did not check the logs though. I assumed that perhaps 0 would be set to some default value.
Can not answer about your observation.It also makes me wonder.
Finally concerning my test setup, I need to configure Tomcat to limit the amount of concurrent
client requests accepted. I need to configure it so that e.g. 300 concurrent clients can connect
but the 301 will not be able to connect (not queued by OS either). That client will see a
failure to connect to server in TCP level.
Do you need more info on this?

Best Regards




________________________________
 From: Christopher Schultz <chris@christopherschultz.net>
To: Tomcat Users List <users@tomcat.apache.org> 
Sent: Wednesday, January 16, 2013 7:52 PM
Subject: Re: Can not understand how maxThreads of Connectors works
 
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Hermes,

On 1/16/13 11:01 AM, Hermes Flying wrote:
> I am trying to understand how the maxThreads attribute of
> Connectors works. I did some tests in order to configure Tomcat to
> limit the number of concurrent client requests (as asked in my
> previous mail).

Please copy anything relevant into this thread. Otherwise the archives
don't work very well.

> Did the following trivial configuration.
> 
> maxThreads=1 and acceptCount=1
> 
> Then I send 2 concurrent requests from 2 clients and both were
> served!

I would expect both to be served: one request was served immediately
(maxThreads=1) and one was queued (acceptCount=1). When the first
request was completed, the second one came out of the queue and was
served.

If you had acceptCount="0" (which may or may not be legal for your
TCP/IP stack) or you had sent 10 simultaneous connections, I would
have expected at least some of them to be dropped with a connection
error (assuming that they really are simultaneous and the response
time is long enough to cover any variance in the connection-attempt time).

Please provide more details about your test setup.

> I was expecting that one would get a network failure!

Woah, you thought you'd take-down your network? You must be running
some shaky hardware.

> I even tried maxThreads=0 and still the clients were served! How is
> this possible?

maxThreads="0" is an illegal configuration. Are you sure Tomcat
started properly? Tomcat 6+ uses an Executor whether you configure one
of not, and the StandardThreadExecutor simply passes the maxThreads
value off to Java's ThreadPoolExecutor, which will throw
IllegalArgumentException if maxThreads is 0.

- -chris
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