Fix panic when region is not found on TiFlash's side in tryFlushData

[CalvinNeo]

What problem does this PR solve?

Issue Number: close #5602

Problem Summary:

1. Region is removed on TiFlash's side, however not on Proxy's side before a restart
2. Proxy replay log, and ask a flush for a region not exist in TiFlash

1. TiFlash implementationAdminCmd::ChangePeer::RemoveNode, the persistence is successful after deleting the region.
2. However, when the proxy persisted meta information to kvdb, the node encountered unexpected downtime.

What is changed and how it works?

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JaySon-Huang
• flowbehappy

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[CalvinNeo]

/cc @JaySon-Huang @flowbehappy @lidezhu

[CalvinNeo]

/run-build-arm64-release comment=true

[lidezhu]

Why this problem just affect v6.2.0?

[CalvinNeo]

Why this problem just affect v6.2.0?

Because in 6.2 we add a tryFlushData to decouple compact log and flushing.

[JaySon-Huang]

Similar to https://kb.pingcap.com/post/articles/92

The root cause of the problem in this kb is that the data dir for proxy has been changed cause by upgrade. But I think this issue is not caused by the data dir change, but could happen after TiFlash restart several times?

[CalvinNeo]

/run-build-arm64-release comment=true

[CalvinNeo]

Similar to https://kb.pingcap.com/post/articles/92

The root cause of the problem in this kb is that the data dir for proxy has been changed cause by upgrade. But I think this issue is not caused by the data dir change, but could happen after TiFlash restart several times?

Like the following

1. TiFlash implementationAdminCmd::ChangePeer::RemoveNode, the persistence is successful after deleting the region.
2. However, when the proxy persisted meta information to kvdb, the node encountered unexpected downtime.

[CalvinNeo]

/run-all-tests

[sre-bot]

download tiflash binary(linux arm64) at http://fileserver.pingcap.net/download/builds/pingcap/test/tiflash/master/3af34398b58bca308cd604f8fbc820eca5cde2d4/centos7/tiflash-linux-arm64.tar.gz

[sre-bot]

Coverage for changed files

Filename                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
KVStore.cpp                       499                65    86.97%          43                 3    93.02%         685                90    86.86%         188                61    67.55%
tests/gtest_kvstore.cpp           311                43    86.17%          28                 2    92.86%        1309                33    97.48%          28                23    17.86%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                             810               108    86.67%          71                 5    92.96%        1994               123    93.83%         216                84    61.11%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
19248      9240             52.00%    218840  93994        57.05%

full coverage report (for internal network access only)

[lidezhu]

Seems this line

tiflash/dbms/src/Storages/Transaction/KVStore.cpp

Line 348 in 2b8d356

throw Exception(fmt::format("region not found when trying flush", ErrorCodes::LOGICAL_ERROR));

should be
throw Exception("region not found when trying flush", ErrorCodes::LOGICAL_ERROR);

[CalvinNeo]

/run-all-tests

[sre-bot]

Coverage for changed files

Filename                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
KVStore.cpp                       499                65    86.97%          43                 3    93.02%         685                90    86.86%         188                61    67.55%
tests/gtest_kvstore.cpp           312                43    86.22%          28                 2    92.86%        1314                33    97.49%          28                23    17.86%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                             811               108    86.68%          71                 5    92.96%        1999               123    93.85%         216                84    61.11%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
19248      9240             52.00%    218845  93965        57.06%

full coverage report (for internal network access only)

[JaySon-Huang]

lgtm

[CalvinNeo]

/run-all-tests

[JaySon-Huang]

/run-unit-test

[CalvinNeo]

/merge

[ti-chi-bot]

@CalvinNeo: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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[ti-chi-bot]

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

Commit hash: a54fe0c

[JaySon-Huang]

/run-unit-test

[CalvinNeo]

/run-unit-test

[sre-bot]

Coverage for changed files

Filename                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
KVStore.cpp                       499                66    86.77%          43                 3    93.02%         685                90    86.86%         188                63    66.49%
tests/gtest_kvstore.cpp           312                43    86.22%          28                 2    92.86%        1314                33    97.49%          28                23    17.86%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                             811               109    86.56%          71                 5    92.96%        1999               123    93.85%         216                86    60.19%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
19247      9238             52.00%    218812  93950        57.06%

full coverage report (for internal network access only)

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #5611.

[sre-bot]

Coverage for changed files

Filename                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
KVStore.cpp                       499                65    86.97%          43                 3    93.02%         685                90    86.86%         188                61    67.55%
tests/gtest_kvstore.cpp           312                43    86.22%          28                 2    92.86%        1314                33    97.49%          28                23    17.86%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                             811               108    86.68%          71                 5    92.96%        1999               123    93.85%         216                84    61.11%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
19247      9236             52.01%    218812  93936        57.07%

full coverage report (for internal network access only)