Fixes race condition that caused unneeded user compactions to run #4554
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The following is an example of the problem this change fixes
1. Thread 1: A user compaction is currently running for a tablet
2. Thread 2: Tablet server receives a compaction request RPC from manager and it
checks to see if the compaction is needed for the same tablet. If finds it is needed.
3. Thread 1: completes user compaction, so a compaction is no longer
needed for the tablet
4. Thread 2: Initiates a user compaction of the tablet because its
check in step 2 passed.
This change adds a second check in step 4 above that should prevent this race
condition because the check is done at a point when its known no
concurrent user compaction is running. The original check was left as a
fail fast check, but a comment was added explaining its not sufficient
for correctness.
matthpeterson
approved these changes
May 13, 2024
dlmarion
approved these changes
May 13, 2024
Contributor
dlmarion
left a comment
dlmarion
left a comment
There was a problem hiding this comment.
Looks good to me. I looked at the existing code and this seems ok.
alerman
approved these changes
May 13, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
5 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The following is an example of the problem this change fixes
This change adds a second check in step 4 above that should prevent this race condition because the check is done at a point when its known no concurrent user compaction is running. The original check was left as a fail fast check, but a comment was added explaining its not sufficient for correctness.