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• The close(timeout) should work when called from a user caller thread or the internal sender thread.
• In sender thread only close(0, TimeUnit.MILLISECONDS) should be called because:
  
  • close() should not be called because that will make producer block forever.
  • close(500, TimeUnit.MILLISECONDS) has the same effect as close(0, TimeUnit.MILLISECONDS) only except it will block for 500 milliseconds.
• IMPORTANT, for the reason above, if a close() or close(timeout, TimeUnit) is called from sender thread (i.e. callback). An error message will be logged and close(0, TimeUnit.MILLISECONDS) will be called instead.
• Because it is possible the close(timeout) is called for multiple times, it has to be idempotent.

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If sender thread calls close(), it will block forever. So if a close() call is called from sender thread, an error message will be put in the log and sender thread will be blocked forever. This is to:

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close(0) will be called instead.

Compatibility, Deprecation, and Migration Plan

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