improve(go.d/proxysql): add hostgroup summary metrics

[ilyam8]

Summary

This PR:

1. Adding hostgroup as a label to all backend charts for better grouping and filtering
2. Adding new per-hostgroup metrics that show the count of backends in each state (ONLINE, SHUNNED, OFFLINE_SOFT, OFFLINE_HARD)

Test Plan

Additional Information

For users: How does this change affect me?

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Summary by cubic

Adds hostgroup-level summary metrics to the ProxySQL collector and labels all backend charts with hostgroup for easier grouping and filtering. Also exposes per-hostgroup counts of backends by status and manages charts dynamically as hostgroups change.

• New Features
  • New chart: proxysql.hostgroup_backends_status (online, shunned, offline_soft, offline_hard), labeled by hostgroup.
  • Added hostgroup label to all backend charts.
  • Collector tracks hostgroups in cache and adds/removes hostgroup charts automatically.

^{Written for commit 2974dcd. Summary will update on new commits.}

[Copilot]

Pull request overview

This PR enhances the ProxySQL collector by adding hostgroup-level summary metrics to provide better visibility into backend server groupings and their health status.

Changes:

• Added per-hostgroup metrics showing counts of backends in each status (ONLINE, SHUNNED, OFFLINE_SOFT, OFFLINE_HARD)
• Added hostgroup label to all backend charts for improved filtering and grouping
• Implemented dynamic hostgroup chart management using a cache-based approach

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
metadata.yaml	Defines new hostgroup metric schema and adds hostgroup label to backend metrics
cache.go	Introduces hostgroupCache struct and management methods for tracking hostgroups
collector.go	Initializes the hostgroups cache map in the collector constructor
collect.go	Implements logic to count backends per hostgroup by status and manages hostgroup chart lifecycle
charts.go	Adds hostgroup chart templates and chart creation/removal methods; updates backend charts to include hostgroup label
collector_test.go	Adds comprehensive test expectations for the new hostgroup metrics and validates chart-metric alignment

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[cubic-dev-ai]

1 issue found across 6 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="src/go/plugin/go.d/collector/proxysql/charts.go">

<violation number="1" location="src/go/plugin/go.d/collector/proxysql/charts.go:654">
P2: `removeHostgroupCharts` matches hostgroups by a prefix that is missing the trailing `_`, so removing hostgroup `1` will also delete charts for hostgroup `10` and any other ID sharing that prefix.</violation>
</file>

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