tso: fix the corner case that may cause TSO fallback (#4885)

[ti-chi-bot]

This is an automated cherry-pick of #4885

Signed-off-by: JmPotato ghzpotato@gmail.com

What problem does this PR solve?

Issue Number: Close #4884.

This bug will occur when the following conditions are met:

1. PD-0 resigns the leader.
2. PD-0 updates the TSO right after resetting it concurrently and leaves the non-empty TSO in memory.
3. PD-0 becomes the leader again.
4. PD-0 receives a TSO request after the leadership is available and before the TSO synchronization is done.
5. A smaller TSO will be generated with this request.
6. BOOM!!!

What is changed and how does it work?

tso: fix the corner case that may cause TSO fallback

Do not update the TSO in memory if it's zero.

Check List

Tests

• Unit test
• Integration test

Release note

Fix the corner case that may cause TSO fallback.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JmPotato
• disksing

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[codecov]

Codecov Report

Merging #4894 (13c6b41) into release-5.0 (bcf3615) will increase coverage by 0.20%.
The diff coverage is 75.00%.

@@               Coverage Diff               @@
##           release-5.0    #4894      +/-   ##
===============================================
+ Coverage        74.89%   75.09%   +0.20%     
===============================================
  Files              245      245              
  Lines            24447    24452       +5     
===============================================
+ Hits             18309    18363      +54     
+ Misses            4515     4482      -33     
+ Partials          1623     1607      -16     

Flag	Coverage Δ
unittests	75.09% <75.00%> (+0.20%)	⬆️

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

Impacted Files	Coverage Δ
server/server.go	72.71% <50.00%> (+0.27%)	⬆️
server/tso/tso.go	78.78% <100.00%> (+6.39%)	⬆️
server/schedule/operator/step.go	68.45% <0.00%> (-0.95%)	⬇️
client/client.go	72.24% <0.00%> (-0.28%)	⬇️
server/grpc_service.go	46.94% <0.00%> (-0.23%)	⬇️
server/tso/allocator_manager.go	75.24% <0.00%> (+0.16%)	⬆️
server/cluster/cluster.go	82.79% <0.00%> (+0.38%)	⬆️
server/schedule/placement/rule_manager.go	83.73% <0.00%> (+0.60%)	⬆️
server/core/storage.go	69.20% <0.00%> (+0.76%)	⬆️
... and 7 more

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[JmPotato]

/merge

[ti-chi-bot]

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

/run-all-tests

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

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

Commit hash: 119f3a2

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

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.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[JmPotato]

/run-unit-tests