[jboss-dev-forums] [Design of JBoss/Tomcat Integration] - Re: JBossWeb-based load metrics for mod_cluster

[bstansberry@jboss.com]

Just an FYI on clustered webapps:

JBossCacheManagerMBean exposes two different attributes re: the session count:


  |    /**
  |     * Gets the number of sessions active on this node.  This includes
  |     * replicated sessions that have not been accessed on this node.
  |     */
  |    long getActiveSessionCount();
  |    
  |    /**
  |     * Gets the count of sessions known to this manager, excluding those
  |     * in the distributed stored that have not been accessed on this node.
  |     */
  |    long getLocalActiveSessionCount();
  | 

I'll have to check if it also exposes via some JMX magic the standard "ActiveSessions" metric you are looking for.  If not, I'll make sure it does. It will return the same value as getActiveSessionCount().

Re: using these in a load balance metric, if the intent of a session count metric is to function as a semi-proxy for memory usage, getting the ActiveSessionCount value does that best, as it includes sessions in the distributed cache, which are using ~ the same memory as a locally active session.

If the intent of the metric is to somehow use a session count as a representation of some other kind of system load, then LocalActiveSessionCount is probably better.

Perhaps a flag on the metric bean could control this? With logic built in to handle the non-clustered webapps that don't support LocalActiveSessionCount?

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