effect-facet-unstable-observability-prometheusmetrics

name	effect-facet-unstable-observability-prometheusmetrics
description	Guidance for facet `effect/unstable/observability/PrometheusMetrics` focused on APIs like layerHttp, format, and HttpOptions. Load after `effect-skill-router` when this facet is the primary owner.

Effect Facet unstable/observability/PrometheusMetrics

Owned scope

• Owns only effect/unstable/observability/PrometheusMetrics.
• Parent module: effect/unstable/observability.
• Source anchor: packages/effect/src/unstable/observability/PrometheusMetrics.ts.

What it is for

• Prometheus metrics exporter for Effect's Metric system.

API quick reference

• layerHttp
• format
• HttpOptions
• FormatOptions
• MetricNameMapper
• formatUnsafe
• Full API list: references/api-reference.md

How to use it

• Prefer pipe-based composition to keep transformations explicit and testable.
• Assume unstable APIs can evolve quickly; isolate usage behind thin local adapters.
• Use the reference docs to select the smallest API surface that solves your task.
• Validate behavior against existing tests before introducing new usage patterns.

Starter example

import { Effect, Metric } from "effect";
import * as PrometheusMetrics from "effect/unstable/observability/PrometheusMetrics";

const program = Effect.gen(function* () {
  // Create and update metrics
  const counter = Metric.counter("http_requests_total", {
    description: "Total HTTP requests",
  });
  yield* Metric.update(counter, 42);

  // Format metrics for Prometheus
  const output = yield* PrometheusMetrics.format();
  console.log(output);
  // # HELP http_requests_total Total HTTP requests
  // # TYPE http_requests_total counter
  // http_requests_total 42
});

Common pitfalls

• Unsafe APIs bypass checks; prefer safe variants unless you control invariants explicitly.
• Unstable module contracts may change; avoid coupling core app logic directly to experimental details.

Not covered here

• Sibling facets under the same parent are out of scope:
  • effect-facet-unstable-observability-otlp (effect/unstable/observability/Otlp)
  • effect-facet-unstable-observability-otlpexporter (effect/unstable/observability/OtlpExporter)
  • effect-facet-unstable-observability-otlplogger (effect/unstable/observability/OtlpLogger)
  • effect-facet-unstable-observability-otlpmetrics (effect/unstable/observability/OtlpMetrics)
  • effect-facet-unstable-observability-otlpresource (effect/unstable/observability/OtlpResource)
  • effect-facet-unstable-observability-otlpserialization (effect/unstable/observability/OtlpSerialization)
  • effect-facet-unstable-observability-otlptracer (effect/unstable/observability/OtlpTracer)
• Parent module ownership belongs to effect-module-unstable-observability.

Escalate to

• effect-module-unstable-observability for parent module-wide workflows.
• effect-skill-router for cross-module routing and ownership checks.

Reference anchors

• Facet source: packages/effect/src/unstable/observability/PrometheusMetrics.ts
• Parent tests: packages/effect/test/unstable/observability/PrometheusMetrics.test.ts
• Parent tests: packages/effect/test/unstable/observability/OtlpMetrics.test.ts
• Parent tests: packages/effect/test/Tracer.test.ts
• API details: references/api-reference.md
• Usage notes: references/usage-reference.md
• Ownership mapping: references/owner.md