[jboss-jira] [JBoss JIRA] Commented: (JBMESSAGING-1399) Allow users to configure a system wide maximum session limit

[Jay Howell (JIRA)]

    [ https://jira.jboss.org/jira/browse/JBMESSAGING-1399?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12422059#action_12422059 ] 

Jay Howell commented on JBMESSAGING-1399:
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I think this is a good shot at functionality for different connection factories.

1.  non-clustered connection factory(includes resource adapter) - So after the connection is created, if  a user tries to create a session an exception will be thrown that says something like "Max Session Reached.  Max Number of Sessions are ?".  No more sessions will be able to be created once the max is reached.  if someone closes a session, then another will be available.  One of the things that will happen if MDBs are involved is that you may see this message over and over again until the sessions are satisfied for the mdbs. The MDBs might not be able to get all of their sessions, so they may have to wait for available sessions.

2.  clustered connection factory. - When a session is created on a server that is already at max session capacity, a new connection should be established to another server(usually they are round robbined) and a session should be established.  If no sessions are available in the cluster, then an exception will be thrown when trying to get an exception. 

> Allow users to configure a system wide maximum session limit
> ------------------------------------------------------------
>
>                 Key: JBMESSAGING-1399
>                 URL: https://jira.jboss.org/jira/browse/JBMESSAGING-1399
>             Project: JBoss Messaging
>          Issue Type: Feature Request
>          Components: Configuration and Management
>            Reporter: Jay Howell
>            Assignee: Tim Fox
>             Fix For: 2.0.0. GA
>
>
> Goal: keep external/internal clients from running the system out of resources(threads/memory).
> We currently have a problem where there is no limit to the number of sessions that can be created in the system.  It would be theoretically possible to have an external client create 1 million sessions in one connection and run the sever out of resources.   It's also possible to set the number of max sessions for an mdb high enough to run the system out of resources(threads/memory).  We need to be able to set a limit for the number of sessions for the system. 
> I've looked at other Messaging systems, like IBM MQ and it seems that other systems have the same setting. 
> We've had users naively suggest that we could implement this by using a bounded thread pool.  This seems too intrusive and too dangerous to do.  This can be done by limiting the number of sessions in the system, which seems like a much better suggestion.  This is much better than using a bounded thread pool for many reasons.  A couple of the reasons is..
> 1.  It doesn't expose the internal workings of JBM to the management console(leaky abstraction).  
> 2.  Users can understand a session limit easier than having to understand the internal thread pool implementation.
> 3.  Doesn't incur deadlocks
> 4.  Allows All clients to get back a message that says some thing like "Session limit reached".
> JBM 2.0 uses an unbounded thread pool for threads, which addresses any concern any performance difficulties with creating and destroying threads.  So now we can address the max number of threads in the system by configuring max sessions in the system.
> Setting a session limit seems to be a more reasonable approach than the bounded thread pool

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