Limiting the number of connection threads per application

[Ken Dombeck <kd...@gearworks.com>]

We have 2 applications installed inside the same Tomcat 5.0 instance
app1 and app2. URL app1.url.com is for app1 and app2.url.com is for
app2. Both URLs have the same ip address but still hit port 80. The
maxThreads for the connector is set to 100. 
 
The problem we are experiencing is that app2 will slow down and consume
all 100 of the connector threads. What we would like to do is limit the
number of threads that each application can use to 50 so that one
application can not cause a denial of service attack to the other
applications in the container. By limiting the number of connections to
50 we would expect the 51st connection to that application to wait until
a thread freed up.
 
I know that I can create multiple connectors in the same service in the
server.xml but they would then have to listen on different ports and we
need both URLs to be listening on port 80. I have read that we could put
Apache in front of Tomcat and it could route the requests to the correct
port in Tomcat based on URL if we had multiple connectors listening on
different ports but we would like to just use Tomcat without anything
else.
 
Does any one know how to configure Tomcat to limit the number of
connections per application within the container?
 

Re: Limiting the number of connection threads per application

[Greg Ward <gw...@python.net>]

On 04 May 2006, Ken Dombeck said:
> We have 2 applications installed inside the same Tomcat 5.0 instance
> app1 and app2. URL app1.url.com is for app1 and app2.url.com is for
> app2. Both URLs have the same ip address but still hit port 80. The
> maxThreads for the connector is set to 100. 
>  
> The problem we are experiencing is that app2 will slow down and consume
> all 100 of the connector threads. What we would like to do is limit the
> number of threads that each application can use to 50 so that one
> application can not cause a denial of service attack to the other
> applications in the container. By limiting the number of connections to
> 50 we would expect the 51st connection to that application to wait until
> a thread freed up.

Wow, I asked this very same question just the other day.  
Tim Funk <funkman at joedog dot org> kindly provided the following
suggestion:

> An "easier solution" is to throttle the webapp via a filter. For example:
> 
> Filter{
>   final int maxThreadCount=10;
>   int threadCount=0;
>   doFilter() {
>     synchronized(this) {
>       if (threadCount>maxThreadCount) {
>         response.sendError(SC_SERVICE_UNAVAILABLE);
>         return;
>       }
>       threadCount++;
>     }
>     try {
>       chain.doFilter(request, response);
>     } finally {
>       synchronized(this) {
>         threadCount--;
>       }
>     }
>   }
> }

I have implemented something like this for us and it works like a
charm.  Haven't got it into production yet though.

Oh yeah, Tim's pseudo-code has an off-by-one error in it: I ended up
using the equivalent of

  doFilter() {
    synchronized(this) {
      if (threadCount >= maxThreadCount) {
        response.sendError(SC_SERVICE_UNAVAILABLE);
        ...


And if your problem is at the level of whole webapps, make sure you
apply the filter to whole webapps.  Here's a snippet from my web.xml
that configures this filter:

    <!--
    Filter to throttle the number of concurrent requests across the
    whole webapp.
    -->
    <filter>
      <filter-name>throttle</filter-name>
      <filter-class>com.intelerad.web.lib.RequestThrottler</filter-class>
      <init-param>
        <param-name>max_concurrent_requests</param-name>
        <param-value>5</param-value>
      </init-param>
    </filter>

    <filter-mapping>
      <filter-name>throttle</filter-name>
      <url-pattern>/*</url-pattern>
    </filter-mapping>

The <filter-mapping> is the important part to make sure it covers a
whole webapp.

        Greg

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

Re: Limiting the number of connection threads per application

[Filip Hanik - Dev Lists <de...@hanik.com>]

create a filter

Ken Dombeck wrote:
> We have 2 applications installed inside the same Tomcat 5.0 instance
> app1 and app2. URL app1.url.com is for app1 and app2.url.com is for
> app2. Both URLs have the same ip address but still hit port 80. The
> maxThreads for the connector is set to 100. 
>  
> The problem we are experiencing is that app2 will slow down and consume
> all 100 of the connector threads. What we would like to do is limit the
> number of threads that each application can use to 50 so that one
> application can not cause a denial of service attack to the other
> applications in the container. By limiting the number of connections to
> 50 we would expect the 51st connection to that application to wait until
> a thread freed up.
>  
> I know that I can create multiple connectors in the same service in the
> server.xml but they would then have to listen on different ports and we
> need both URLs to be listening on port 80. I have read that we could put
> Apache in front of Tomcat and it could route the requests to the correct
> port in Tomcat based on URL if we had multiple connectors listening on
> different ports but we would like to just use Tomcat without anything
> else.
>  
> Does any one know how to configure Tomcat to limit the number of
> connections per application within the container?
>  
>
>   


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