prometheus-gin

Prometheus + Gin Example

Demonstrates how to use idem.WithMetrics to export idempotency middleware metrics to Prometheus. The application uses in-memory storage and exposes counters for cache hits, misses, lock contentions, and storage errors.

Run

docker compose up --build

This starts:

• app on localhost:8080 — Gin application with idem middleware and /metrics endpoint
• prometheus on localhost:9090 — Prometheus server scraping the app every 5 seconds

Try it

# 1. Send a request — cache miss, handler executes
curl -X POST http://localhost:8080/orders -H "Idempotency-Key: key-123"
# => {"message":"order created","order_id":"order-1"}

# 2. Same key — cache hit, cached response returned
curl -X POST http://localhost:8080/orders -H "Idempotency-Key: key-123"
# => {"message":"order created","order_id":"order-1"}

# 3. Check metrics
curl http://localhost:8080/metrics | grep idem_
# => idem_cache_hits_total 1
# => idem_cache_misses_total 1

Open Prometheus UI at http://localhost:9090 and query:

• idem_cache_hits_total
• idem_cache_misses_total
• idem_lock_contentions_total
• idem_storage_errors_total

Metrics

Metric	Type	Description
idem_cache_hits_total	Counter	Idempotency cache hits (cached response returned)
idem_cache_misses_total	Counter	Idempotency cache misses (handler executed)
idem_lock_contentions_total	Counter	Lock contentions resulting in 409 Conflict
idem_storage_errors_total	Counter	Storage operation errors

Stop

docker compose down