metrics: support multi-k8s in grafana dashboards

[just1900]

Signed-off-by: just1900 legendj228@gmail.com

What problem does this PR solve?

Issue Number: close #4673

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

Code changes

• Has configuration change
• Has HTTP API interfaces change (Don't forget to add the declarative for API)
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• tidb metrics: Support multi k8s in grafana dashboards pingcap/tidb#32546
• tikv metrics: support multi k8s in grafana dashboards tikv#12008
• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tiup:
• Need to cherry-pick to the release branch

Release note

metrics: support multi-k8s in grafana dashboards

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• nolouch
• rleungx

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[nolouch]

Could you add an issue link? and there must reference other components.

[codecov]

Codecov Report

Merging #4671 (c33512f) into master (6231567) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4671      +/-   ##
==========================================
- Coverage   74.76%   74.74%   -0.02%     
==========================================
  Files         284      284              
  Lines       27816    27816              
==========================================
- Hits        20796    20791       -5     
- Misses       5152     5154       +2     
- Partials     1868     1871       +3     

Flag	Coverage Δ
unittests	74.74% <ø> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
pkg/errs/errs.go	75.00% <0.00%> (-25.00%)	⬇️
pkg/tempurl/tempurl.go	45.00% <0.00%> (-15.00%)	⬇️
server/id/id.go	76.19% <0.00%> (-4.77%)	⬇️
server/tso/tso.go	63.06% <0.00%> (-4.55%)	⬇️
pkg/etcdutil/etcdutil.go	82.35% <0.00%> (-3.53%)	⬇️
tools/pd-ctl/pdctl/command/operator.go	66.66% <0.00%> (-1.15%)	⬇️
server/encryptionkm/key_manager.go	72.90% <0.00%> (-0.80%)	⬇️
server/server.go	74.19% <0.00%> (-0.65%)	⬇️
server/handler.go	50.81% <0.00%> (-0.41%)	⬇️
client/client.go	68.89% <0.00%> (+0.10%)	⬆️
... and 6 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6231567...c33512f. Read the comment docs.

[rleungx]

Do we have any test of this PR?

[just1900]

Could you add an issue link? and there must reference other components.

I've added the tidb-operator issue link and PRs for other components into description.

Do we have any test of this PR?

Manual tested by load it to my grafana, it works fine.

[nolouch]

/merge

[ti-chi-bot]

@nolouch: 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: c33512f

[nolouch]

/run-cherry-picker

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #4717.