Boxes: Use temporary lock file to prevent early unregister #244
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Following the RFC 4122, there should not be any brackets in UUID string
…race In parallel run of multi-machine environment the same box image could be cloning simultaneously by more then one envs. So, the box should be unregister by the latest env. To prevent a race condition here, we add a temporary lease file with a counter. It is incremented for incoming envs (new clones) and decremented after the cloning. The last env removes the lock file and unregisters the box. Fixes ParallelsGH-243
It guarantees that counter is written on the disk and IO buffer is flushed.
…s to box lease file
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Boxes: Use temporary lock file to prevent early unregister
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Fixes GH-243
In parallel run of multi-machine environment the same box image could be cloning
simultaneously by more then one envs. But the box should be unregister exactly by the last env.
To prevent a race condition here, we add a temporary lease file with a counter.
It is incremented for incoming envs (new clones) and decremented right after the cloning.
The last env removes the lock file and unregisters the box.
cc: @racktear @Gray-Wind @Kasen