AckManager.flush would hold a lock on ackManager, There was a possible deadlock with MirrorTarget:
Thread 1:
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AckManager.addRetry(AckManager.java:393)
- waiting to lock <0x00000007990a13e8> (a org.apache.activemq.artemis.protocol.amqp.connect.mirror.AckManager)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AckManager.ack(AckManager.java:418)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AMQPMirrorControllerTarget.performAck(AMQPMirrorControllerTarget.java:479)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AMQPMirrorControllerTarget.postAcknowledge(AMQPMirrorControllerTarget.java:461)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AMQPMirrorControllerTarget.actualDelivery(AMQPMirrorControllerTarget.java:318)
at org.apache.activemq.artemis.protocol.amqp.proton.ProtonAbstractReceiver.onMessageComplete(ProtonAbstractReceiver.java:361)
Thread 2:
at jdk.internal.misc.Unsafe.park(java.base@11.0.8/Native Method)
- parking to wait for <0x000000079de0af38> (a java.util.concurrent.CountDownLatch$Sync)
at java.util.concurrent.locks.LockSupport.parkNanos(java.base@11.0.8/LockSupport.java:234)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedNanos(java.base@11.0.8/AbstractQueuedSynchronizer.java:1079)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireSharedNanos(java.base@11.0.8/AbstractQueuedSynchronizer.java:1369)
at java.util.concurrent.CountDownLatch.await(java.base@11.0.8/CountDownLatch.java:278)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AMQPMirrorControllerTarget.flush(AMQPMirrorControllerTarget.java:230)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AckManager$$Lambda$601/0x00000008005c3040.accept(Unknown Source)
at java.lang.Iterable.forEach(java.base@11.0.8/Iterable.java:75)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AckManager.flushMirrorTargets(AckManager.java:184)
- locked <0x00000007990a13e8> (a org.apache.activemq.artemis.protocol.amqp.connect.mirror.AckManager)
at org.apache.activemq.artemis.protocol.amqp.connect.mirror.AckManager.initRetry(AckManager.java:162)
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