fix: Fix inconsistency when deleting dash entries #1734
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Partially addresses #1730. Beforehand we removed entries from mcflag only inside DbSlice::Del function but we delete entries in other cases too (like expiration) and in this case we left dangling entries in mcflag table. The fix adds the deletion of mcflag entries into PerformDeletion function. It by itself does not explain the crash but dangling entries cause UB (because the keys are references to non-existent PrimeKeys) so maybe this somehow causes inconsistency where a key is not present in mcflags. I am not sure I fixed the original issue but I surely fixed a corruption bug. In addition, I removed the redundant check fail and added error logs to follow up on this later. Signed-off-by: Roman Gershman <[email protected]>
kostasrim
approved these changes
Aug 24, 2023
| @@ -38,6 +38,13 @@ void PerformDeletion(PrimeIterator del_it, ExpireIterator exp_it, EngineShard* s | |||
| table->expire.Erase(exp_it); | |||
| } | |||
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| if (del_it->second.HasFlag()) { | |||
| if (table->mcflag.Erase(del_it->first) == 0) { | |||
| LOG(ERROR) << "Internal error, inconsistent state, mcflag should be present but not found " | |||
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Not sure how this affect the rest of the execution of this function, but if this is an internal error, shouldn't we also return from this function and not continue?
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we try to delete it anyway. This internal error is not fatal, at least it does not seem so.
| @@ -38,6 +38,13 @@ void PerformDeletion(PrimeIterator del_it, ExpireIterator exp_it, EngineShard* s | |||
| table->expire.Erase(exp_it); | |||
| } | |||
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| if (del_it->second.HasFlag()) { | |||
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Small nit you can squash the two if's under one condition with &&. Not sure if this is imposed by our style guide or if this is purely a stylistic opinion. Ignore me if this is not useful.
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specifically here I prefer to leave it as is :)
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Partially addresses #1730.
Beforehand we removed entries from mcflag only inside DbSlice::Del function but we delete entries in other cases too (like expiration) and in this case we left dangling entries in mcflag table. The fix adds the deletion of mcflag entries into PerformDeletion function.
It by itself does not explain the crash but
dangling entries cause UB (because the keys are references to non-existent PrimeKeys) so maybe this somehow causes inconsistency where a key is not present in mcflags.
I am not sure I fixed the original issue but I surely fixed a corruption bug. In addition, I removed the redundant check fail and added error logs to follow up on this later.