prevent proxy locking while snapshotting#8131
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timvisee
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That's a subtle change! Looks good. I see we now only hold a lock on the segment to clone the wrapped segment for a very short period of time.
I did not re-test the deadlock locally, and am assuming you've done that already.
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yes, it is enough to just send update requests to block everything |
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* [manual] do not lock proxy segmen while accessing wrapped segment * fmt * [manual] remove extra update lock
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This PR rolls back changes of #7196
Why it is problematic?
Why it should be ok not to hold the lock?
Proxy segments are design explicitly for this situation - allow read + write operations, while underlying segment is accessed for read for a long time. This is how optimization functions.
Requiring it to be locked for the same duration as wrapped segment essentially kills the idea of proxy segment.
Extra changes of a new updates lock for the duration of proxifying didn't show any improvement, but I think it might be good to have anyway - it prevents update operation from reading/writing directly into wrapped segments after they are already proxified.☝️ this doesn't work because of deadlock on parallel snapshots