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EtcdWorker: fix EtcdWorker snapshot isolation (#2510) #2557

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This is an automated cherry-pick of #2510

What problem does this PR solve?

  • EtcdWorker's snapshot isolation is violated if there are two concurrent transactions one deleting and the other putting to the same key.
  • EtcdWorker's snapshot isolation is violated if while A is running and trying to create a key k, B and C creates and deletes k sequentially.

What is changed and how it works?

  • For the first case, we use equality of mod_revision to check for write-set intersection instead of inequality.
  • For the second case, we use a global deleteCounter as a key to make deletions impossible to race with other operations.

Check List

Tests

  • Unit test
  • Integration test

Code changes

  • Has persistent data change

Side effects

  • Possible performance regression
  • Increased code complexity

Related changes

  • Need to cherry-pick to the release branch

Release note

Fix a bug in metadata management

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[REVIEW NOTIFICATION]

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@ti-chi-bot ti-chi-bot added release-note Denotes a PR that will be considered when it comes time to generate release notes. do-not-merge/cherry-pick-not-approved component/scheduler TiCDC inner scheduler component. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. status/LGT2 Indicates that a PR has LGTM 2. type/bugfix This PR fixes a bug. labels Aug 17, 2021
@ti-chi-bot ti-chi-bot added the type/cherry-pick-for-release-4.0 This PR is cherry-picked to release-4.0 from a source PR. label Aug 17, 2021
@nongfushanquan nongfushanquan added cherry-pick-approved Cherry pick PR approved by release team. and removed do-not-merge/cherry-pick-not-approved labels Aug 18, 2021
@amyangfei amyangfei added this to the v4.0.15 milestone Aug 18, 2021
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/merge

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This pull request has been accepted and is ready to merge.

Commit hash: 5715964

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label Aug 18, 2021
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/run-integration-tests
/run-kafka-tests

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/run-kafka-tests

@ti-chi-bot ti-chi-bot merged commit 0c3ebe1 into pingcap:release-4.0 Aug 19, 2021
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cherry-pick-approved Cherry pick PR approved by release team. component/scheduler TiCDC inner scheduler component. release-note Denotes a PR that will be considered when it comes time to generate release notes. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. status/can-merge Indicates a PR has been approved by a committer. status/LGT2 Indicates that a PR has LGTM 2. type/bugfix This PR fixes a bug. type/cherry-pick-for-release-4.0 This PR is cherry-picked to release-4.0 from a source PR.
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4 participants