feat(metrics): add requests_per_prefix_total counter#556
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emadolsky
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Pull request overview
Adds an opt-in Prometheus counter to measure how often /render requests directly reference configured metric-name prefixes, enabling per-prefix request volume tracking when requestsPerPrefixList is set in API config.
Changes:
- Introduces
requestsPerPrefixListAPI configuration for validated per-prefix counting. - Adds
requests_per_prefix_total{prefix=...}Prometheus counter and registers it. - Implements per-request prefix matching in
renderHandler, plus unit tests for prefix matching and prefix-list validation.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| pkg/cfg/api.go | Adds RequestsPerPrefixList YAML config field and documentation. |
| pkg/app/carbonapi/metrics.go | Defines and registers the requests_per_prefix_total CounterVec. |
| pkg/app/carbonapi/http_handlers.go | Implements prefix matching in /render and increments the counter. |
| pkg/app/carbonapi/http_handlers_test.go | Adds tests for metricRefsPrefix and initRequestPrefixes. |
| pkg/app/carbonapi/app.go | Stores validated prefixes on App and adds initRequestPrefixes validation helper. |
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Adds a configurable per-prefix counter on /render. Each request
increments requests_per_prefix_total{prefix=...} once per configured
prefix that is directly referenced by one of its target metric
patterns (metric == prefix, or metric starts with '<prefix>.').
Configured via the new requestsPerPrefixList yaml key on the api
side. Empty/glob entries are dropped at startup. Field is nil by
default — feature stays silent until configured.
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deniszh
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Jun 17, 2026
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Adds a configurable per-prefix counter on /render. Each request increments requests_per_prefix_total{prefix=...} once per configured prefix that is directly referenced by one of its target metric patterns (metric == prefix, or metric starts with '.').
Configured via the new requestsPerPrefixList yaml key on the api side. Empty/glob entries are dropped at startup. Field is nil by default — feature stays silent until configured.
What issue is this change attempting to solve?
How does this change solve the problem? Why is this the best approach?
How can we be sure this works as expected?