You are viewing a plain text version of this content. The canonical link for it is here.

Posted to dev@tomcat.apache.org by brien colwell <xc...@gmail.com> on 2007/12/01 23:22:58 UTC

max number of concurrent requests

hi all,

I'm building a framework that needs to block on HTTP requests. That is, 
at some point when executing my servlet, the thread will wait for some 
event to happen. Of course this wait may be very long. Is there a limit 
to threads in Tomcat? Is there a mechanism to yield processing a 
request, and then pick it up later?

Sorry if this is unclear ...

Thanks,
Brien


---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@tomcat.apache.org
For additional commands, e-mail: dev-help@tomcat.apache.org

Re: max number of concurrent requests

Posted by brien colwell <xc...@gmail.com>.

hi Christophe,

Comet seems like it's addressing the issues I have ... it looks like it is
implemented with a fixed-size pool of active threads, each dispatching
events to what could be an unbounded number of listeners ...  I'm going to
try a scale test with Comet and report back ...

Stepping back, the number of long lived HTTP connections seems bounded by
only the number of concurrent TCP/IP connections supported.  I'm not sure
how Comet determines whether there is new data on a socket, but it seems
this could be done on a single thread. That is, using
asynchronous/non-blocking sockets.

My requirements are actually a bit less than what Comet appears to support.
My protocol requires the client to send data only in the beginning of a
session ... I might be able to use that to get more performance out of the
framework ...

Thanks,
Brien

On Dec 16, 2007 12:34 PM, Christophe Pierret <cp...@sparus-software.com>
wrote:

> Brien,
> Depending on the HTTP connector you use (may be basic HTTP, APR or NIO)
> and whether you use the comet API or not, the limit to number of maximum
> concurrent long-lived connections in tomcat may be very different.
> In my experience, the most scalable is with:
> 1) NIO + comet or APR + comet
> 2) APR or NIO without comet
> 3) standard HTTP connector
>
> The OS you are running onto has also an impact.
> For example, with standart HTTP connector (default one) on a Linux Red Hat
> 4 , dual cpu box with 2Gb of RAM (under VMWare), we managed to run a
> successful 3000 concurrent HTTP requests (long running HTTP requests) at a
> customer site. The same box under Windows was behind, but it may due to our
> inability to tune it?
> We had to tune the linux system and the JVM to reach those numbers, but
> your load may differ from that of our application and you may get very
> different numbers: plan some testing ahead ...
> The system limits you usually bump into:
> 1) max number of threads per process
> 2) max memory per process (use java option -Xss to reduce thread stack
> size and -Xmx to up the java heap size, tune the corresponding system limit)
> 3) max file descriptors per process
> There are many others that I don't have at the top of my mind right now...
> Type "man ulimit" at your linux prompt to get some more hints.
>
> Using comet + NIO or APR, you may break these barriers by not using one
> thread per long-lived request.
>
> I hope this helps and points you to some area of research.
>
> Best regards,
> Christophe Pierret
>
> -----Message d'origine-----
> De: brien colwell [mailto:xcolwell@gmail.com]
> Envoyé: samedi 1 décembre 2007 23:23
> À: dev@tomcat.apache.org
> Objet: max number of concurrent requests
>
> hi all,
>
> I'm building a framework that needs to block on HTTP requests. That is,
> at some point when executing my servlet, the thread will wait for some
> event to happen. Of course this wait may be very long. Is there a limit
> to threads in Tomcat? Is there a mechanism to yield processing a
> request, and then pick it up later?
>
> Sorry if this is unclear ...
>
> Thanks,
> Brien
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: dev-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: dev-help@tomcat.apache.org
>
>

RE: max number of concurrent requests

Posted by Christophe Pierret <cp...@sparus-software.com>.

Brien,
Depending on the HTTP connector you use (may be basic HTTP, APR or NIO) and whether you use the comet API or not, the limit to number of maximum concurrent long-lived connections in tomcat may be very different.
In my experience, the most scalable is with:
1) NIO + comet or APR + comet
2) APR or NIO without comet
3) standard HTTP connector

The OS you are running onto has also an impact.
For example, with standart HTTP connector (default one) on a Linux Red Hat 4 , dual cpu box with 2Gb of RAM (under VMWare), we managed to run a successful 3000 concurrent HTTP requests (long running HTTP requests) at a customer site. The same box under Windows was behind, but it may due to our inability to tune it?
We had to tune the linux system and the JVM to reach those numbers, but your load may differ from that of our application and you may get very different numbers: plan some testing ahead ...
The system limits you usually bump into:
1) max number of threads per process
2) max memory per process (use java option -Xss to reduce thread stack size and -Xmx to up the java heap size, tune the corresponding system limit)
3) max file descriptors per process
There are many others that I don't have at the top of my mind right now...
Type "man ulimit" at your linux prompt to get some more hints.

Using comet + NIO or APR, you may break these barriers by not using one thread per long-lived request.

I hope this helps and points you to some area of research.

Best regards,
Christophe Pierret

-----Message d'origine-----
De : brien colwell [mailto:xcolwell@gmail.com]
Envoyé : samedi 1 décembre 2007 23:23
À : dev@tomcat.apache.org
Objet : max number of concurrent requests

hi all,

I'm building a framework that needs to block on HTTP requests. That is,
at some point when executing my servlet, the thread will wait for some
event to happen. Of course this wait may be very long. Is there a limit
to threads in Tomcat? Is there a mechanism to yield processing a
request, and then pick it up later?

Sorry if this is unclear ...

Thanks,
Brien

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@tomcat.apache.org
For additional commands, e-mail: dev-help@tomcat.apache.org