Reproduce an MDB with maxSessions=1 that stops consuming after its work is rejected

[rzo1]

Reproducer for the "MDB pool drops instances on RejectedExecutionException" thread on dev@. Not meant to be merged as is. The test fails on purpose.

What the test does

The ActiveMQ resource adapter gets threadPoolSize=2, QueueSize=1 and OfferTimeout=1 second.

1. A blocking MDB occupies both pool threads and the single queue slot.
2. A message is sent to an MDB with maxSessions=1. Scheduling its ServerSession work is rejected after the offer timeout.
3. The blocking MDB is released, so the pool recovers.
4. Another message is sent to the maxSessions=1 MDB. It is never consumed.

With -DofferTimeout="30 seconds" the work only waits and is never rejected, and the test passes. The rejection is what kills the consumer.

mvn -pl container/openejb-core test -Dtest=MdbWorkRejectionTest
mvn -pl container/openejb-core test -Dtest=MdbWorkRejectionTest -DofferTimeout="30 seconds"

Analysis

The code involved is identical in 10.2.0 (activemq-ra 6.2.7, geronimo-connector 4.0.0) and on main (activemq-ra 6.3.2).

• geronimo-connector 4.0.0: GeronimoWorkManager.executeWork lets RejectedExecutionException escape. ServerSessionImpl.start() only catches WorkException, so running stays true. The session stays in activeSessions without a thread and is never considered stale. With maxSessions=1 the consumer is dead for good; with more sessions a slot leaks per rejection. Nothing is logged.
• With GERONIMO-6911 (apache/geronimo-txmanager#10, verified with a local 4.0.1-SNAPSHOT via -Dversion.geronimo.components=4.0.1-SNAPSHOT): start() fails with a JMSException, which reaches the exception listener of ActiveMQEndpointWorker. The listener disconnects and calls connect(), which schedules the reconnect on the same, still saturated WorkManager. On WorkException it sets running = false and logs "Work Manager did not accept work", so the endpoint never reconnects. The test fails the same way, with this sequence in the log:

WARN  Failed to schedule work for session ServerSessionImpl:{...}, marking not running (WorkRejectedException)
ERROR Connection to broker failed: Start failed: jakarta.resource.spi.work.WorkRejectedException: The execution has been rejected.
ERROR Work Manager did not accept work: (WorkRejectedException)

Both holes are in activemq-ra (ServerSessionImpl.start() and ActiveMQEndpointWorker.connect()), so the fix most likely belongs upstream.