[jboss-jira] [JBoss JIRA] (WFLY-9524) Messaging - default max client threads

[Jeff Mesnil (JIRA)]

    [ https://issues.jboss.org/browse/WFLY-9524?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13489921#comment-13489921 ] 

Jeff Mesnil commented on WFLY-9524:
-----------------------------------

Is that a practical issue?

On my laptop, I have 8 CPU cores, this means:
- 64 client threads (8 * 8)
- 32 MDBs (4 * 8)
- 15 JCA sessions

Do we have actual cases with only 1 CPU core?

> Messaging - default max client threads
> --------------------------------------
>
>                 Key: WFLY-9524
>                 URL: https://issues.jboss.org/browse/WFLY-9524
>             Project: WildFly
>          Issue Type: Enhancement
>          Components: JMS
>    Affects Versions: 11.0.0.Final
>            Reporter: Martin Styk
>            Assignee: Jeff Mesnil
>
> By default, size of client thread pool is configured as 8 * number of CPU cores.
> On 1 CPU machine, with default configuration and MDB deployed on server, resource starvation is possible
> On one CPU there are by default
> * 8 ActiveMQ client threads (8 * CPU count)
> * 4 MDB instances (mdb-strict-max-pool = 4 * CPU count)
> * 15 JCA RA sessions consuming messages from queue (default value of maxSession)
> Consuming of messages by MDB gets stuck because all 8 client threads are awaiting large message completion and there is no other thread to handle other tasks.
> {code:title=Client thread waiting for large message completion}
> "Thread-7 (ActiveMQ-client-global-threads)" #475 daemon prio=5 os_prio=0
> tid=0x000000000590f000 nid=0x7c7a in Object.wait() [0x00007fda43413000]
>       java.lang.Thread.State: TIMED_WAITING (on object monitor)
>            at java.lang.Object.wait(Native Method)
>            at
>            org.apache.activemq.artemis.core.client.impl.LargeMessageControllerImpl.waitCompletion(LargeMessageControllerImpl.java:302)
>            - locked <0x00000000b0083e88> (a
>            org.apache.activemq.artemis.core.client.impl.LargeMessageControllerImpl)
>            at
>            org.apache.activemq.artemis.core.client.impl.LargeMessageControllerImpl.saveBuffer(LargeMessageControllerImpl.java:276)
>            - locked <0x00000000b0083e88> (a
>            org.apache.activemq.artemis.core.client.impl.LargeMessageControllerImpl)
>            at
>            org.apache.activemq.artemis.core.client.impl.ClientLargeMessageImpl.checkBuffer(ClientLargeMessageImpl.java:159)
>            at
>            org.apache.activemq.artemis.core.client.impl.ClientLargeMessageImpl.checkCompletion(ClientLargeMessageImpl.java:84)
>            at
>            org.apache.activemq.artemis.jms.client.ActiveMQMessage.doBeforeReceive(ActiveMQMessage.java:786)
>            at
>            org.apache.activemq.artemis.jms.client.ActiveMQTextMessage.doBeforeReceive(ActiveMQTextMessage.java:110)
>            at
>            org.apache.activemq.artemis.ra.inflow.ActiveMQMessageHandler.onMessage(ActiveMQMessageHandler.java:295)
>            at
>            org.apache.activemq.artemis.core.client.impl.ClientConsumerImpl.callOnMessage(ClientConsumerImpl.java:1001)
>            at
>            org.apache.activemq.artemis.core.client.impl.ClientConsumerImpl.access$400(ClientConsumerImpl.java:49)
>            at
>            org.apache.activemq.artemis.core.client.impl.ClientConsumerImpl$Runner.run(ClientConsumerImpl.java:1124)
>            at
>            org.apache.activemq.artemis.utils.OrderedExecutorFactory$OrderedExecutor$ExecutorTask.run(OrderedExecutorFactory.java:122)
>            at
>            java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>            at
>            java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>            at java.lang.Thread.run(Thread.java:748)
> {code}
> This can be fixed by adjusting default values for these parameters.
> In this case, we need more client threads than JCA RA sessions (maxSession). 
> To avoid resource starvation, number of client threads must be greater than sum of {{maxSession}} for each MDB deployed on server.
> We should check number of client threads required by deployments (MDBs), and at least print warning message that size of client thread pool may be insufficient.



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