add DB config max_threads by grpc context

[mengxin9014]

What problem does this PR solve?

Issue Number: close #4794

Problem Summary:

What is changed and how it works?

If set max_threads, it will be pushed down to TiFlash by grpc context to make DB context in a session.

set max_threads =

• -1 : TiFlash will use its own max_threads config;
• 0 : max_threads will be pushed down to TiFlash and it means that the concurrency will determined automatically;
• x(>0) : max_threads will be pushed down to TiFlash and it means that the concurrency will be set to x.

Check List

Tests

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

Release note

add DB config max_threads by grpc context.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• LittleFall
• windtalker

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[windtalker]

LGTM

[mengxin9014]

/merge

[ti-chi-bot]

@mengxin9014: 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.

If you have any questions about the PR merge process, please refer to pr process.

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[ti-chi-bot]

@mengxin9014: /merge in this pull request requires 2 approval(s).

In response to this:

/merge

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.

[mengxin9014]

/merge

[ti-chi-bot]

@mengxin9014: 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.

If you have any questions about the PR merge process, please refer to pr process.

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: a94aeed

[sre-bot]

Coverage for changed files

too many lines from llvm-cov, please refer to full report instead

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
18121      9785             46.00%    202195  97854        51.60%

full coverage report (for internal network access only)