executor,distsql: fix analyze version 2 memory leak (#28729)

[ti-srebot]

cherry-pick #28729 to release-5.1
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/29305

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git push git@github.com:ti-srebot/tidb.git pr/29305:release-5.1-d53f9f55a0f9

---

What problem does this PR solve?

Fix oncall 3776

Problem Summary:

What is changed and how it works?

When error happen during the NextRaw() call, buildSamplingStats returns without close the task channel, cause the subMergeWorker leak and the the memory leak.

What's Changed:

Handle the resource close correctly when error happens.

How it Works:

When error happen, the channel is closed, so the worker goroutine can exit.

I write a test using failpoint to mock the error, before the fix, the test log looks like this:

[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:436] ["topNSlowQueryLoop exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:493] ["topologySyncerKeeper exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:898] ["loadPrivilegeInLoop exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:1025] ["globalBindHandleWorkerLoop exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:1099] ["TelemetryReportLoop exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:947] ["LoadSysVarCacheLoop exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:465] ["infoSyncerKeeper exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:1066] ["handleEvolvePlanTasksLoop exited."]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:649] ["domain closed"] ["take time"=110.679µs]
[2021/10/11 18:46:35.904 +08:00] [INFO] [domain.go:1129] ["TelemetryRotateSubWindowLoop exited."]
[2021/10/11 18:46:35.905 +08:00] [INFO] [db.go:567] ["Closing database"]
[2021/10/11 18:46:35.905 +08:00] [INFO] [db.go:592] ["Memtable flushed"]
[2021/10/11 18:46:35.905 +08:00] [INFO] [db.go:596] ["Compaction finished"]
[2021/10/11 18:46:35.905 +08:00] [INFO] [db.go:615] ["BlobManager finished"]
[2021/10/11 18:46:35.905 +08:00] [INFO] [db.go:619] ["ResourceManager finished"]
[2021/10/11 18:46:35.905 +08:00] [INFO] [db.go:625] ["Waiting for closer"]
PASS
goleak: Errors on successful test run: found unexpected goroutines:
[Goroutine 609 in state chan receive, with github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker on top of the stack:
goroutine 609 [chan receive]:
github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker(0xc0062add40, 0xc0062a3440, 0xc0062a34a0, 0x3, 0x0)
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:1210 +0x55b
created by github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).buildSamplingStats
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:859 +0x693

 Goroutine 608 in state chan receive, with github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker on top of the stack:
goroutine 608 [chan receive]:
github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker(0xc0062add40, 0xc0062a3440, 0xc0062a34a0, 0x3, 0x1)
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:1210 +0x55b
created by github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).buildSamplingStats
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:859 +0x693

 Goroutine 626 in state chan receive, with github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker on top of the stack:
goroutine 626 [chan receive]:
github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker(0xc0062add40, 0xc0062a3440, 0xc0062a34a0, 0x3, 0x0)
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:1210 +0x55b
created by github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).buildSamplingStats
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:859 +0x693

 Goroutine 627 in state chan receive, with github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker on top of the stack:
goroutine 627 [chan receive]:
github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).subMergeWorker(0xc0062add40, 0xc0062a3440, 0xc0062a34a0, 0x3, 0x0)
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:1210 +0x55b
created by github.com/pingcap/tidb/executor.(*AnalyzeColumnsExec).buildSamplingStats
	/home/genius/project/src/github.com/pingcap/tidb/executor/analyze.go:859 +0x693
]
exit status 1
FAIL	github.com/pingcap/tidb/executor/seqtest	0.582s

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

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

Fix a memory leak bug when using @@tidb_analyze_version = 2

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• time-and-fate
• winoros

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[ti-srebot]

/run-all-tests

[ti-srebot]

@tiancaiamao you're already a collaborator in bot's repo.

[tiancaiamao]

/rebuild

[tiancaiamao]

/rebuild

[bb7133]

/merge

[ti-chi-bot]

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

Commit hash: e238810

[bb7133]

/merge

[VelocityLight]

/merge

[tiancaiamao]

Ref #32499