Issue

With our jBPM 3.2 application, we are running into deadlock situations in production, which is reproducible with the following simple test process:

<process-definition  xmlns="urn:jbpm.org:jpdl-3.2"  name="Process_Timer2">
        <start-state name="start-state1">
                <transition to="node1"></transition>
        </start-state>
        <state name="Sleep">
                <timer duedate="1 seconds" name="sleep_timer_2" transition="OK" repeat="NO">
                        <action></action>
                </timer>
                <transition to="node1" name="OK"></transition>
        </state>
        <node name="node1">
                <action class="Wait"></action>
                <transition to="Sleep"></transition>
        </node>
</process-definition>

The Wait class does nothing more than sleep for a second before continuing the execution:

        public void execute(ExecutionContext executionContext) throws Exception {
                Thread.sleep(1000);
                executionContext.leaveNode();
        }

If we run two or more instances of this process definition, after a random time, we can experience this issue. This only happens if jBPM is configured with more than one JobExecutorThread's.

This is the MySQL support response on this incident:

Looks as though 2 holds an X lock on the record while 1 holds the insert intention lock. 2 can't then get the insert intention lock it needs to proceed. 1 can't continue past insert intention because 2 holds the X with a previous change. Deadlock, since neither can proceed.