java.util.ConcurrentModificationException when accessing message headers

[cer]

A rarely occurring problem.

I suspect that it's because TracingMessagingInterceptor is calling Message.setHeader() which is modifying the headers map in place instead of copy on write.

2019-05-22 14:54:27.839  INFO [-,872bce8c71ae4ce4,872bce8c71ae4ce4,false] 40397 --- [    Test worker] i.e.tram.inmemory.InMemoryMessaging      : sending to channel kitchenService that has 1 subscriptions this message io.eventuate.tram.messaging.common.MessageImpl@2de6110f[payload={"orderId":99,"restaurantId":1,"ticketDetails":{"lineItems":[{"menuItemId":"1","name":"Chicken Vindaloo","quantity":5}]}},headers={command_saga_id=4fafb019b3bd16db-1633daefc8566c3e, DATE=Wed, 22 May 2019 21:54:27 GMT, command_type=net.chrisrichardson.ftgo.kitchenservice.api.CreateTicket, X-B3-SpanId=872bce8c71ae4ce4, command_reply_to=net.chrisrichardson.ftgo.orderservice.sagas.createorder.CreateOrderSaga-reply, DESTINATION=kitchenService, command_saga_type=net.chrisrichardson.ftgo.orderservice.sagas.createorder.CreateOrderSaga, X-B3-Sampled=0, X-B3-TraceId=872bce8c71ae4ce4, ID=0000016ae189d57f-aea3cfd9f7110000}] 
2019-05-22 14:54:27.840  INFO [-,872bce8c71ae4ce4,872bce8c71ae4ce4,false] 40397 --- [    Test worker] i.e.tram.inmemory.InMemoryMessaging      : sending to channel kitchenService that has 1 subscriptions this message io.eventuate.tram.messaging.common.MessageImpl@2de6110f[payload={"orderId":99,"restaurantId":1,"ticketDetails":{"lineItems":[{"menuItemId":"1","name":"Chicken Vindaloo","quantity":5}]}},headers={command_saga_id=4fafb019b3bd16db-1633daefc8566c3e, DATE=Wed, 22 May 2019 21:54:27 GMT, command_type=net.chrisrichardson.ftgo.kitchenservice.api.CreateTicket, X-B3-SpanId=872bce8c71ae4ce4, command_reply_to=net.chrisrichardson.ftgo.orderservice.sagas.createorder.CreateOrderSaga-reply, DESTINATION=kitchenService, command_saga_type=net.chrisrichardson.ftgo.orderservice.sagas.createorder.CreateOrderSaga, X-B3-Sampled=0, X-B3-TraceId=872bce8c71ae4ce4, ID=0000016ae189d57f-aea3cfd9f7110000}] 
2019-05-22 14:54:27.845 ERROR [-,,,] 40397 --- [pool-2-thread-1] i.e.tram.inmemory.InMemoryMessaging      : message handler kitchenService

java.util.ConcurrentModificationException: null
	at java.base/java.util.HashMap$EntrySpliterator.forEachRemaining(HashMap.java:1756) ~[na:na]
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) ~[na:na]
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) ~[na:na]
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913) ~[na:na]
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578) ~[na:na]
	at io.eventuate.tram.commands.consumer.CommandDispatcher.correlationHeaders(CommandDispatcher.java:144) ~[eventuate-tram-commands-0.21.0.RELEASE.jar:na]
	at io.eventuate.tram.commands.consumer.CommandDispatcher.messageHandler(CommandDispatcher.java:80) ~[eventuate-tram-commands-0.21.0.RELEASE.jar:na]
	at io.eventuate.tram.sagas.participant.SagaCommandDispatcher.messageHandler(SagaCommandDispatcher.java:47) ~[eventuate-tram-sagas-participant-0.11.1.RELEASE.jar:na]
	at io.eventuate.tram.inmemory.InMemoryMessaging.lambda$null$0(InMemoryMessaging.java:83) ~[eventuate-tram-in-memory-0.20.0.RELEASE.jar:na]
	at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140) ~[spring-tx-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at io.eventuate.tram.inmemory.InMemoryMessaging.lambda$sendToHandlers$1(InMemoryMessaging.java:80) ~[eventuate-tram-in-memory-0.20.0.RELEASE.jar:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135) ~[na:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) ~[na:na]
	at java.base/java.lang.Thread.run(Thread.java:844) ~[na:na]