Prometheus Metrics

NORA exposes Prometheus-compatible metrics at the /metrics endpoint. No authentication is required.

curl http://localhost:4000/metrics

HTTP metrics

Metric	Type	Labels	Description
nora_http_requests_total	Counter	registry, method, status	Total HTTP requests processed
nora_http_request_duration_seconds	Histogram	registry, method	Request latency (buckets: 1ms to 10s)

The registry label is derived from the request path:

Path prefix	Label
/v2*	docker
/npm*	npm
/simple*, /packages*	pypi
/maven2*	maven
/cargo*	cargo
/go/*	go
/raw/*	raw
/gems/*	gems
/terraform/*	terraform
/ansible/*	ansible
/nuget/*	nuget
/pub/*	pub
/conan/*	conan
/ui*	ui
(other paths)	other

Cache metrics

Metric	Type	Labels	Description
nora_cache_requests_total	Counter	registry, result	Cache lookups (hit or miss)

Storage metrics

Metric	Type	Labels	Description
nora_storage_operations_total	Counter	operation, status	Storage operations (get, put, delete, list) with ok or error status
nora_artifacts_total	Counter	registry	Total artifacts stored per registry

Circuit breaker metrics

Available when NORA_CB_ENABLED=true.

Metric	Type	Labels	Description
nora_circuit_breaker_state	Gauge	registry	Current state: 0 = closed, 1 = open, 2 = half-open
nora_circuit_breaker_rejections_total	Counter	registry	Requests rejected by an open breaker

Garbage collection metrics

Metric	Type	Description
nora_gc_blobs_removed_total	Counter	Orphaned blobs removed by GC
nora_gc_bytes_freed_total	Counter	Bytes freed by GC
nora_gc_duration_seconds	Histogram	Duration of GC runs (buckets: 0.1s to 300s)
nora_gc_last_run_timestamp	Gauge	Unix timestamp of last GC run
nora_gc_metadata_phantoms_total	Counter	Phantom version entries cleaned from metadata

Retention metrics

Metric	Type	Description
nora_retention_versions_deleted_total	Counter	Versions removed by retention policies
nora_retention_bytes_freed_total	Counter	Bytes freed by retention
nora_retention_duration_seconds	Histogram	Duration of retention runs (buckets: 0.1s to 300s)
nora_retention_last_run_timestamp	Gauge	Unix timestamp of last retention run

Grafana example

# Request rate by registry (5m window)
sum by (registry) (rate(nora_http_requests_total[5m]))

# Cache hit ratio
sum(rate(nora_cache_requests_total{result="hit"}[5m]))
/
sum(rate(nora_cache_requests_total[5m]))

# p99 latency per registry
histogram_quantile(0.99, sum by (le, registry) (rate(nora_http_request_duration_seconds_bucket[5m])))

# Circuit breaker alerts (open state)
nora_circuit_breaker_state == 1

# GC bytes freed per hour
increase(nora_gc_bytes_freed_total[1h])

Scrape configuration

prometheus.yml

scrape_configs:
  - job_name: nora
    scrape_interval: 15s
    static_configs:
      - targets: ['nora:4000']
    metrics_path: /metrics

See Also

• Settings — NORA_METRICS_ENABLED and related options
• Circuit Breaker — breaker metrics details
• Upgrade Guide — new metrics in v0.9