[BEAM-5759] Ensuring JmsIO checkpoint state is accessed and modified safely

[andrew-flumaion]

As described in BEAM-5759, a ConcurrentModificationException can be thrown when JmsIO source checkpoint finalisation occurs simultaneously to further messages being added for finalisation. This is due to the state of JmsCheckpointMark not being thread safe.

This change adds a unit test which demonstrates the issue by

1. Adding several messages to a queue.
2. Reading some of these messages with an UnboundedJmsReader (which adds messages for finalization).
3. Calling finalizeCheckpoint on the reader's checkpoint mark in a separate thread.
4. Reading the remainder of the messages in parallel with the above finalization.

In order to reliably reproduce this issue, the test uses a JMS consumer which decorates received messages with a callback which sleeps for a short period, introducing some "lag" into the finalization process.

To fix the issue, JmsCheckpointMark has been updated with thread safety constructs. In order to avoid potentially long blocks for consumers during checkpoint finalization, a read/write lock is used and finalization takes a snapshot of state before processing in a lock-free manner, only locking to update state post-finalization.

@jbonofre

Post-Commit Tests Status (on master branch)

Lang	SDK	Apex	Dataflow	Flink	Gearpump	Samza	Spark
Go		---	---	---	---	---	---
Java
Python		---			---	---	---

[andrew-flumaion]

retest this please

[jbonofre]

retest this please

[jbonofre]

LGTM, thanks !