grafana: render stacked nulls as zero

[nizheming]

Summary

Issue Number: close #5009

• set stacked Grafana graph panels to render null points as zero
• avoid misleading stacked visualizations when a series has data gaps

Test

• make generate-next-gen-grafana
• parsed dashboard JSON files
• verified every stack: true graph panel has nullPointMode: "null as zero"

Fix TiCDC Grafana stacked memory usage panels to render null datapoints as zero.

[ti-chi-bot]

Hi @nizheming. Thanks for your PR.

I'm waiting for a pingcap member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[ti-chi-bot]

Welcome @nizheming!

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[coderabbitai]

📝 Walkthrough

Walkthrough

The PR updates the Memory Usage graph panel configuration in two Grafana dashboards. The nullPointMode setting is changed from "null" to "null as zero", modifying how missing data points are rendered in both the standard and next-generation TiCDC monitoring dashboards.

Changes

Grafana Dashboard Null Point Mode Updates

Layer / File(s)	Summary
Dashboard Null Point Mode Configuration metrics/grafana/ticdc_new_arch.json, metrics/nextgengrafana/ticdc_new_arch_next_gen.json	Memory Usage panel nullPointMode changed from "null" to "null as zero" so missing/null datapoints render as zero.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 I nudged one line in JSON bright,
So empty gaps become a light,
Now stacked charts stack without a fear,
Zeros hop in, the view is clear,
A tiny tweak — a joyful byte.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'grafana: render stacked nulls as zero' accurately and concisely describes the main change: configuring Grafana stacked panels to handle null values as zero.
Linked Issues check	✅ Passed	The PR successfully addresses issue #5009 by updating nullPointMode from 'null' to 'null as zero' in both specified Grafana dashboard files for stacked panels as required.
Out of Scope Changes check	✅ Passed	All changes are scoped to Grafana dashboard JSON files and directly address the objective of fixing stacked panel null value rendering, with no unrelated modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description check	✅ Passed	The PR description includes the issue number, clear summary of changes, test verification steps, and a properly formatted release note as required by the template.

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[pingcap-cla-assistant]

All committers have signed the CLA.

[gemini-code-assist]

Code Review

This pull request updates the nullPointMode configuration from null to null as zero in two Grafana dashboard JSON files. The reviewer suggests adopting a templating tool like Grafonnet to manage these dashboards more efficiently and reduce the risk of inconsistencies during manual updates.

[gemini-code-assist]

I notice this same change is applied to metrics/nextgengrafana/ticdc_new_arch_next_gen.json. Having to update multiple dashboard JSON files manually for the same change can be error-prone and increases maintenance overhead.

To improve long-term maintainability, it might be worth exploring generating these Grafana dashboards from a template using a tool like Grafonnet or a custom script. This would reduce duplication and ensure consistency between the dashboard files.

[nizheming]

Issue Number: ref #5009

[nizheming]

Thanks for pointing this out. I reset the generated next-gen JSON, kept the source change in metrics/grafana/ticdc_new_arch.json, then ran make generate-next-gen-grafana from the repo root. The generated output is the same, and I force-pushed an amended commit documenting that flow.

Verification:

• make generate-next-gen-grafana
• parsed metrics/grafana/ticdc_new_arch.json, metrics/nextgengrafana/ticdc_new_arch_next_gen.json, and metrics/nextgengrafana/ticdc_new_arch_with_keyspace_name.json
• verified all stacked graph panels in those files use nullPointMode: "null as zero"

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3AceShowHand, tenfyzhong

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Details

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• OWNERS [3AceShowHand,tenfyzhong]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-05-08 07:45:55.899579083 +0000 UTC m=+426628.772929055: ☑️ agreed by 3AceShowHand.
• 2026-05-08 07:58:53.249978535 +0000 UTC m=+427406.123328507: ☑️ agreed by tenfyzhong.

[tenfyzhong]

/ok-to-test

[ti-chi-bot]

@nizheming: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cdc-kafka-integration-light	cf6d8eb	link	unknown	/test pull-cdc-kafka-integration-light

Full PR test history. Your PR dashboard.

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