session: remove distributed tasks limitation from upgrade

[tangenta]

What problem does this PR solve?

Issue Number: close #54061

Problem Summary:

During the rolling upgrade, when the distributed execution framework is enabled, the add index task is processed, and data indexes may be inconsistent.

The limitation is only a defensive measure based on previous issues, we don't have unsolved data inconsistent issues.

Since the issue is fixed(#50895), and the limitation introduces inconvenience to many users, we should remove the check in the following versions.

What changed and how does it work?

Remove distributed task configuration check before upgrade.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  Before this PR:
  1. Deploy a nightly cluster without TiDB instance.
  2. Start TiDB v7.5.
  3. Set @@global.tidb_enable_dist_task to ON.
  4. Kill TiDB v7.5.
  5. Start TiDB master.
     TiDB cannot startup and report error:

  [FATAL] [bootstrap.go:1495] ["cannot upgrade when tidb_enable_dist_task is enabled, please set tidb_enable_dist_task to off before upgrade"] [] [stack="github.com/pingcap/tidb/pkg/session.checkDistTask\n\t/home/tangenta/tidb/pkgsession/bootstrap.go:1495\ngithub.com/pingcap/tidb/pkg/session.upgrade\n\t/home/tangenta/tidb/pkg/session/bootstrap.go:1538\ngithub.com/pingcap/tidb/pkg/session.runInBootstrapSession\n\t/home/tangenta/tidb/pkg/session/sessiongo:3738\ngithub.com/pingcap/tidb/pkg/session.bootstrapSessionImpl\n\t/home/tangenta/tidb/pkg/session/session.go:3460\ngithub.com/pingcap/tidb/pkg/session.BootstrapSession\n\t/home/tangenta/tidb/pkg/session/session.go:3406\nmaincreateStoreDDLOwnerMgrAndDomain\n\t/home/tangenta/tidb/cmd/tidb-server/main.go:418\nmain.main\n\t/home/tangenta/tidb/cmd/tidb-server/main.go:321\nruntime.main\n\t/home/tangenta/go/pkg/mod/golang.org/[email protected]/src/runtime/proc.go:272"]
  

  After this PR, we removed the check checkDistTask, TiDB can startup and upgrade normally:

  mysql> select tidb_version();
  +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | tidb_version()                                                                                                                                                                                                  |
  +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Release Version: v8.4.0-this-is-a-placeholder
  Edition: Community
  Git Commit Hash: None
  Git Branch: None
  UTC Build Time: None
  GoVersion: go1.23.2
  Race Enabled: false
  Check Table Before Drop: false
  Store: tikv |
  +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  1 row in set (0.00 sec)
  
  mysql> select @@global.tidb_enable_dist_task;
  +--------------------------------+
  | @@global.tidb_enable_dist_task |
  +--------------------------------+
  |                              1 |
  +--------------------------------+
  1 row in set (0.00 sec)
  

• No need to test

  • I checked and no code files have been changed.

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

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.5476%. Comparing base (d0d4876) to head (0fb6cb3).
Report is 795 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #56773        +/-   ##
================================================
+ Coverage   73.0457%   73.5476%   +0.5019%     
================================================
  Files          1689       1689                
  Lines        467009     467739       +730     
================================================
+ Hits         341130     344011      +2881     
+ Misses       104894     102800      -2094     
+ Partials      20985      20928        -57     

Flag	Coverage Δ
integration	42.8521% <ø> (?)
unit	72.5880% <ø> (+0.0551%)	⬆️

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Components	Coverage Δ
dumpling	∅ <ø> (∅)
parser	∅ <ø> (∅)
br	46.8007% <ø> (-0.0476%)	⬇️

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-10-23 02:54:14.362076563 +0000 UTC m=+406055.058867167: ☑️ agreed by D3Hunter.
• 2024-11-13 08:50:12.555777351 +0000 UTC m=+432574.746646348: ☑️ agreed by wjhuang2016.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: benmeadowcroft, D3Hunter, wjhuang2016

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Needs approval from an approver in each of these files:

• OWNERS [D3Hunter,wjhuang2016]
• pkg/session/OWNERS [benmeadowcroft]

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #59285.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #59286.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #61954.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #61955.
But this PR has conflicts, please resolve them!