sessionctx: avoid IMDS leak in TestSetTiDBCloudStorageURI

[D3Hunter]

What problem does this PR solve?

Issue Number: ref #65526

Problem Summary:
TestSetTiDBCloudStorageURI is flaky in CI because it can trigger AWS IMDS credential probing when validating s3://blackhole without explicit credentials. The test assertions pass, but background HTTP connection goroutines from that probe can still be alive when goleak runs, causing intermittent shard failures.

What changed and how does it work?

This PR adds a test-scoped environment guard in TestSetTiDBCloudStorageURI:

• t.Setenv("AWS_EC2_METADATA_DISABLED", "true")

This disables EC2 IMDS probing only for this test process, removing the flaky goroutine source while keeping the existing behavior checks and assertions unchanged.

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

None

Summary by CodeRabbit

• Tests
  • Improved test stability by configuring environment settings to prevent unnecessary background operations during test execution.

[ti-chi-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 6296c1ff-28b9-4fa7-b991-d153b6a9acfb

📥 Commits

Reviewing files that changed from the base of the PR and between 078b070 and 92939d9.

📒 Files selected for processing (1)

• pkg/sessionctx/variable/tests/session_test.go

---

📝 Walkthrough

Walkthrough

A test in the session variable module now sets the AWS_EC2_METADATA_DISABLED environment variable before executing the TestSetTiDBCloudStorageURI test. This prevents the AWS SDK from initiating background HTTP metadata lookups during test execution.

Changes

Cohort / File(s)	Summary
Test Environment Configuration pkg/sessionctx/variable/tests/session_test.go	Added t.Setenv("AWS_EC2_METADATA_DISABLED", "true") to disable AWS IMDS metadata probing during the test, preventing unwanted background goroutines from spawning.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A test once danced with AWS in the night,
Background goroutines spawning out of sight,
But now with DISABLED=true, we set it right,
No more metadata chasing—clean and tight! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: disabling IMDS leak in a specific test function. It is concise, directly related to the changeset, and helps teammates understand the primary fix.
Description check	✅ Passed	The description is comprehensive and follows the template structure. It includes issue number, clear problem summary, explanation of the fix, completed checklist with unit test marked, and release notes section marked as 'None'.

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Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.11.4)

Command failed

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[tiprow]

Hi @D3Hunter. Thanks for your PR.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.5060%. Comparing base (ee3439d) to head (92939d9).
⚠️ Report is 22 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #67604        +/-   ##
================================================
- Coverage   77.7488%   77.5060%   -0.2429%     
================================================
  Files          1959       1964         +5     
  Lines        543393     551953      +8560     
================================================
+ Hits         422482     427797      +5315     
- Misses       120070     124142      +4072     
+ Partials        841         14       -827     

Flag	Coverage Δ
integration	40.9044% <ø> (+4.7296%)	⬆️
unit	76.6461% <ø> (+0.2611%)	⬆️

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

Components	Coverage Δ
dumpling	61.5065% <ø> (ø)
parser	∅ <ø> (∅)
br	50.4239% <ø> (-10.5901%)	⬇️

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[D3Hunter]

/retest

[tiprow]

@D3Hunter: PRs from untrusted users cannot be marked as trusted with /ok-to-test in this repo meaning untrusted PR authors can never trigger tests themselves. Collaborators can still trigger tests on the PR using /test.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: joechenrh, lance6716

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Needs approval from an approver in each of these files:

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-04-08 07:05:34.768467341 +0000 UTC m=+939939.973827388: ☑️ agreed by joechenrh.
• 2026-04-08 08:04:00.480043928 +0000 UTC m=+943445.685403995: ☑️ agreed by lance6716.