Fix DB iterator not resetting pauserehash causing dict being unable to rehash #12757
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…o rehash When using DB iterator, it will use dictInitSafeIterator to init a old safe dict iterator. When dbIteratorNext is used, it will jump to the next slot db dict when we are done a dict. During this process, we do not have any calls to dictResumeRehashing, which causes the dict's pauserehash to always be > 0. And at last, it will be returned directly in dictRehashMilliseconds, which causes us to have slot dict in a state where rehash cannot be completed. In the "expire scan should skip dictionaries with lot's of empty buckets" test, adding a `keys *` can reproduce the problem stably. `keys *` will call dbIteratorNext to trigger a traversal of all slot dicts. Added dbReleaseIterator and dbIteratorInitNextSafeIterator methods to call dictResetIterator. Issue was introduced in redis#11695.
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Good catch! 👍 |
oranagra
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Nov 14, 2023
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thanks for finding this.
minor code arrangement comment before merging...
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good catch |
oranagra
approved these changes
Nov 14, 2023
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When using DB iterator, it will use dictInitSafeIterator to init a old safe
dict iterator. When dbIteratorNext is used, it will jump to the next slot db
dict when we are done a dict. During this process, we do not have any calls to
dictResumeRehashing, which causes the dict's pauserehash to always be > 0.
And at last, it will be returned directly in dictRehashMilliseconds, which causes
us to have slot dict in a state where rehash cannot be completed.
In the "expire scan should skip dictionaries with lot's of empty buckets" test,
adding a
keys *can reproduce the problem stably.keys *will call dbIteratorNextto trigger a traversal of all slot dicts.
Added dbReleaseIterator function to call dictResetIterator.
Issue was introduced in #11695.