metrics: support multi-k8s in grafana dashboards (#4099)

[just1900]

What problem does this PR solve?

resolve conflicts when cherry-pick #4099, and this is a continuation of #4206 to bypass repo permission restrictions.

Issue Number: ref #4129

Problem Summary:

K8s community and organizations are increasingly deploying multiple Kubernetes clusters to improve availability, isolation and scalability. Since TiDB Operator have support deploying tidb across-kubernetes, this PR will address the multi-k8s issue without affecting existing single-cluster use case.

What is changed and how it works?
What's Changed:

• add a k8s_cluster label in all expr

• add k8s_cluster variable in Grafana templating
  How it works:

• For users with single-k8s, nothing need to be changed, just use it as before.

• For users with multi-k8s:

  • first add kubernetes label to identify k8s cluster in your prometheus' external_labels.
  • set field "hide" to '0' to show variables in grafana via sed -i s/"hide": 2/"hide": 0/g <path/to/dashboard.json>
  • load it to grafana

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

metrics: support multi-k8s in grafana dashboards

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JaySon-Huang
• flowbehappy

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[JaySon-Huang]

/merge

[ti-chi-bot]

@JaySon-Huang: 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: 0827ad7

[ti-chi-bot]

@just1900: Your PR was out of date, I have automatically updated it for you.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.

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