wagoe.observability.metrics.shell.adapters.prometheus — com.wagoe/wagoe-observability 1.0.0-beta-5

Pure-Clojure Prometheus metrics adapter.

An in-memory metric registry that renders the Prometheus text exposition format (https://prometheus.io/docs/instrumenting/exposition_formats/). It implements all four metrics protocols (IMetricsRegistry, IMetricsEmitter, IMetricsExporter, IMetricsConfig) in a single component backed by one Clojure atom, so it is safe for concurrent use via swap!.

No external Prometheus client dependency is used — the exposition text is produced by this namespace directly.

Sanitization + collisions (BOU-207): metric/label names are sanitized to valid Prometheus identifiers. Post-sanitization COLLISIONS are handled so the output stays valid:

• Metric names: if a later registration sanitizes to the same name as an already-registered different key (e.g. :http.requests then :http-requests, both -> http_requests), the later one is logged and IGNORED — the first registration wins (no duplicate # TYPE line).
• Label keys within a series: keys that sanitize to the same label name are de-duplicated deterministically at render (the lexicographically-first [name value] pair wins), so no duplicate label appears in a series.

Series identity

Each metric value is keyed by (metric-name, label-set), where the label-set is the merge of the registry default tags, the metric's registration tags, and any per-call tags. Distinct label-sets are therefore distinct series.

Metric storage

• counter : {label-set -> numeric total}
• gauge : {label-set -> numeric value (last write wins)}
• histogram: {label-set -> {:counts {bucket -> n} :inf n :sum s :count c}} (per-bucket non-cumulative counts; cumulative counts are computed at export time)
• summary : {label-set -> {:sum s :count c}} — quantiles are NOT tracked; only the _sum/_count pair is emitted (see note below).

Simplifications

• Summary quantiles are not computed. A summary emits only _sum and _count, which is a valid (if minimal) Prometheus summary exposition.
• Metric names are emitted as-is (assumed already valid Prometheus names).

create-metrics-component clj

(create-metrics-component)

(create-metrics-component config)

Create a Prometheus metrics component implementing all four metrics protocols, backed by a single atom.

Args: config - Prometheus provider config map (see wagoe.observability.metrics.schema/PrometheusMetricsConfig). Recognised keys: :histogram-buckets, :include-help-text, :registry-name, and :tagging {:default-tags {...}}.

Returns: Component implementing IMetricsRegistry, IMetricsEmitter, IMetricsExporter, and IMetricsConfig.

create-metrics-components clj

(create-metrics-components)

(create-metrics-components config)

Create a complete set of Prometheus metrics components that all share a single underlying component/atom, so registration, emission, export, and config operate on the same state.

Returns: {:registry IMetricsRegistry :emitter IMetricsEmitter :exporter IMetricsExporter :config IMetricsConfig}

create-metrics-config clj

(create-metrics-config)

(create-metrics-config config)

Create a Prometheus metrics config (a full component; all protocols share one atom). See create-metrics-component.

create-metrics-emitter clj

(create-metrics-emitter)

(create-metrics-emitter config)

Create a Prometheus metrics emitter (a full component; all protocols share one atom). See create-metrics-component.

create-metrics-exporter clj

(create-metrics-exporter)

(create-metrics-exporter config)

Create a Prometheus metrics exporter (a full component; all protocols share one atom). See create-metrics-component.

create-metrics-registry clj

(create-metrics-registry)

(create-metrics-registry config)

Create a Prometheus metrics registry (a full component; all protocols share one atom). See create-metrics-component.