Synchronization of RestrictionTrackers

[Jan Lukavský]

Hi,

I have come across something that looks like a bug to me, but I'm not 
sure of that. If I understand it correctly, 
RestrictionTracker.trySplit() and RestrictionTracker.tryClaim() methods 
are necessarily called from different threads. That implies, that 
modifying some fields inside these methods might require 
synchronization. Looking here [1], I didn't find anything that should 
ensure atomicity and consistency of these methods. If anything I'd 
expect the lastClaimedOffset and lastAttemptedOffset be volatile. But 
probably the problem is deeper. Is this a bug, or am I missing something?

 Jan

[1] 
https://github.com/apache/beam/blob/939fa99ce943a30da46cb3d67c924d524fbf1be4/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/splittabledofn/OffsetRangeTracker.java#L44