*: support coprocessor cache for paging protocol

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #35786

Problem Summary:

What is changed and how it works?

The paging protocol breaks coprocessor cache (when I enable paging), now I'd like to bring it back.

It works like this:

1. For coprocessor paging request, the cache key will add an extra 'paging=1' byte.

2. After receiving the cop paging response, the cache value will store both the Data and the paging Range.

3. When the cop paging request hit cache, it will recover both Data and Range information.

4. So after the handleCopTask, it update the paging range to the next one.

In a work, each of the paging request is cached and reused seperately.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu
• xhebox

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[tiancaiamao]

/run-check-issue-triage-complete

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/9f7128a13ae0e4b5ac319a0a3f8acb4807d3235c

[tiancaiamao]

One compatibility issue I found is that in the old setting, CheckResponseAdmission will cache coprocessor request whose ProcessTime is longer than 5ms

While in the paging protocol, for many cases, the segmented page request takes less than 5ms and is thus not cached.

[xhebox]

One compatibility issue I found is that in the old setting, CheckResponseAdmission will cache coprocessor request whose ProcessTime is longer than 5ms

While in the paging protocol, for many cases, the segmented page request takes less than 5ms and is thus not cached.

I think it is transparent to users. So it is only a behavior change for us. Maybe we could use two different timing parameters for stream/paging.

[wshwsh12]

Should we set resp.pbResp.Range = nil when cacheValue.PageStart/PageEnd == nil?

[XuHuaiyu]

/merge

[XuHuaiyu]

/merge cancel

[tiancaiamao]

/run-check_dev_2

[tiancaiamao]

/merge

[ti-chi-bot]

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

Commit hash: f7f8f88

[tiancaiamao]

/run-check_dev_2

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! New failing [2] after this pr merged.
These new failed integration tests seem to be caused by the current PR, please try to fix these new failed integration tests, thanks!

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	🟥 failed 1, success 10, total 11	24 min	New failing
idc-jenkins-ci-tidb/common-test	🟥 failed 1, success 11, total 12	12 min	New failing
idc-jenkins-ci/integration-cdc-test	🟢 all 35 tests passed	27 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	6 min 41 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 42 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	5 min 31 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	5 min 12 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 21 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 11 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed