config: set max token limit to 1M

[djshow832]

What problem does this PR solve?

Issue Number: close #53312

Problem Summary:
If a user sets token-limit to a big value, TiDB will OOM.

What changed and how does it work?

If the token-limit is bigger than 1M, set it to 1M.
It won't report errors so it's compatible with previous versions.
One TiDB instance won't have over 1M concurrent queries because that will mean at least 1M goroutines and file descriptors.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• 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.

- Lower the max value of `token-limit` to 1048576 to avoid OOM

[tiprow]

Hi @djshow832. Thanks for your PR.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.7039%. Comparing base (491740b) to head (7de9cfa).
Report is 8 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #53361        +/-   ##
================================================
+ Coverage   72.5147%   73.7039%   +1.1892%     
================================================
  Files          1498       1523        +25     
  Lines        429925     436146      +6221     
================================================
+ Hits         311759     321457      +9698     
+ Misses        98883      94778      -4105     
- Partials      19283      19911       +628     

Flag	Coverage Δ
integration	49.2172% <0.0000%> (?)
unit	71.3547% <100.0000%> (-0.0563%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	53.9957% <ø> (ø)
parser	∅ <ø> (∅)
br	42.5655% <ø> (+0.9645%)	⬆️

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-17 08:59:56.383601141 +0000 UTC m=+1816550.140736710: ☑️ agreed by Defined2014.
• 2024-05-17 10:54:32.89082933 +0000 UTC m=+1823426.647965070: ☑️ agreed by xhebox.

[djshow832]

/retest

[tiprow]

@djshow832: 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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[djshow832]

/ok-to-test

[easonn7]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Defined2014, easonn7, xhebox

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• OWNERS [Defined2014,xhebox]
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