I am using the following Apache config to forward requests to a Tomcat server:
ProxyPass /myapp ajp://localhost:8009/myapp max=2
This is a simplified config, but is enough to reproduce the issue, which is that the max parameter has no effect. If I through 10 concurrent requests to Apache, all 10 are forwarded to Tomcat at the same time, while I would like to have them forwarded 2 by 2. Should I use something other than the max parameter for this?
The max=2 failed to limit the number of requests concurrently forwarded to Tomcat because I was running this on UNIX, and my Apache came preconfigured with prefork MPM, which creates one process per request. The max applies per process, hence doesn't have the desired effect.
If you are in this situation and need to limit the number concurrent request forwarded to Tomcat, then you'll need to replace your Apache with a worker or event MPM Apache, in the config set ServerLimit to 1, and ThreadsPerChild and MaxClients to the same value, which will be the total number of concurrent connections your Apache will be able to process. You can find more information about this in this section documenting the recommended Apache configuration for Orbeon Forms.