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ddl: add owner_id field to tidb_mdl_info to avoid unexpected writes #53234

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merged 5 commits into from
May 15, 2024

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@tangenta tangenta commented May 13, 2024

What problem does this PR solve?

Issue Number: close #53073

Problem Summary:

tidb-1 keeps printing "someone is not synced", which means it is blocked at waitSchemaSynced.

[2024/05/13 17:24:32.067 +08:00] [INFO] [syncer.go:352] ["syncer check all versions, someone is not synced"] [category=ddl] [info="instance ip tc-tidb-1.tc-tidb-peer.endless-ha-test-add-index-tps-7576420-1-811.svc, port 4000, id d3ac6d21-0137-4106-b42a-89692b7ba7e1"] ["ddl job id"=791] [ver=1931]

tidb-1 is DDL owner. However, tidb-1's schema version is less than non-owner TiDB (here are the results from tiup ctl:v8.0.0 etcd --endpoints={pd_addr}:2379 get --prefix /tidb/ddl):

/tidb/ddl/all_schema_by_job_versions/791/5bd21551-75b9-4a47-86d4-9520ce74cfd3
1931
/tidb/ddl/all_schema_by_job_versions/791/d3ac6d21-0137-4106-b42a-89692b7ba7e1
1930
...
/tidb/ddl/fg/owner/66018f542345e63b
d3ac6d21-0137-4106-b42a-89692b7ba7e1

After checking the log, I found that DDL owner is switched from tidb-0 to tidb-1 at this time.

On the other hand, mysql.tidb_mdl_info is empty.

Above all, the timeline should be:

1. tidb-0 gets owner
2. tidb-0 registers mdl info
3. tidb-0 waits schema sync

4. tidb-1 gets owner from tidb-0

5. tidb-1 register mdl info
6. tidb-0 clean mdl info
7. tidb-1 wait schema sync, block...

At step 6, tidb-0 incorrectly clean the mdl info registered by tidb-1. As a result, there is nothing to update in mdlCheckLoop because tidb_mdl_info is empty.

What changed and how does it work?

  • Add owner_id field to tidb_mdl_info to identify which owner is used.
  • Prevent updating unexpected mdl info by specifying owner_id in WHERE clause.

Check List

Tests

Side effects

  • Performance regression: Consumes more CPU
  • Performance regression: Consumes more Memory
  • Breaking backward compatibility

Documentation

  • Affects user behaviors
  • Contains syntax changes
  • Contains variable changes
  • Contains experimental features
  • Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

@ti-chi-bot ti-chi-bot bot added do-not-merge/needs-linked-issue do-not-merge/needs-tests-checked release-note-none size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels May 13, 2024
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tiprow bot commented May 13, 2024

Hi @tangenta. Thanks for your PR.

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codecov bot commented May 13, 2024

Codecov Report

Attention: Patch coverage is 75.00000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 75.7191%. Comparing base (4fe70da) to head (b5778b6).
Report is 21 commits behind head on master.

Additional details and impacted files
@@               Coverage Diff                @@
##             master     #53234        +/-   ##
================================================
+ Coverage   72.4796%   75.7191%   +3.2395%     
================================================
  Files          1493       1497         +4     
  Lines        429362     434379      +5017     
================================================
+ Hits         311200     328908     +17708     
+ Misses        98931      84952     -13979     
- Partials      19231      20519      +1288     
Flag Coverage Δ
integration 50.5253% <50.0000%> (?)
unit 71.6804% <75.0000%> (+0.3015%) ⬆️

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Components Coverage Δ
dumpling 53.9957% <ø> (ø)
parser ∅ <ø> (∅)
br 61.5948% <ø> (+20.1545%) ⬆️

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/retest

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tiprow bot commented May 13, 2024

@tangenta: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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/ok-to-test

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ti-chi-bot bot commented May 15, 2024

[LGTM Timeline notifier]

Timeline:

  • 2024-05-15 05:52:37.776124805 +0000 UTC m=+1632511.533260378: ☑️ agreed by YuJuncen.
  • 2024-05-15 06:26:11.340125757 +0000 UTC m=+1634525.097261328: ☑️ agreed by wjhuang2016.

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easonn7 commented May 15, 2024

/approve

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ti-chi-bot bot commented May 15, 2024

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: easonn7, wjhuang2016, YuJuncen

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@ti-chi-bot ti-chi-bot bot added the approved label May 15, 2024
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/retest

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@tangenta
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/retest

@ti-chi-bot ti-chi-bot bot merged commit 4538a21 into pingcap:master May 15, 2024
32 checks passed
ti-chi-bot pushed a commit to ti-chi-bot/tidb that referenced this pull request May 15, 2024
Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
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In response to a cherrypick label: new pull request created to branch release-8.1: #53300.

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