Go URL Shortener

A high performance URL shortener written in Go to explore distributed systems fundamentals: observability, scalability, deployment, and testing.

👉 I document what I learn from each pull request in LEARNINGS.md.

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At a glance

• REST API built with chi, request timeouts, and graceful shutdown.
• SQLite persistence with embedded Goose migrations; data stored in data/app.db.
• In-memory LRU cache for hot redirect lookups.
• Idempotent create flow when clients reuse X-Request-ID.
• Observability: Zap JSON logs, Prometheus metrics at /metrics, and a local Grafana stack.
• Testing: table-driven unit tests with sqlmock plus integration tests via httptest.

Quick Start

Run the server:

go run ./cmd/server

Override the port:

PORT=9090 go run ./cmd/server

API

Endpoints:

Method	Endpoint	Description	Status / Utility
POST	/shorten	Create a shortened URL from a long link	Core API
GET	/r/{code}	Redirect to the original destination	Core API
GET	/metrics	Prometheus metrics for monitoring	DevOps
GET	/health	Liveness probe (Server is alive)	Kubernetes/Health
GET	/readyz	Readiness probe (DB is connected)	Kubernetes/Health

Example:

curl -X POST http://localhost:8080/shorten \
  -H 'Content-Type: application/json' \
  -d '{"url":"https://example.com"}'

Response:

{"short":"http://localhost:8080/r/abc123"}

Full OpenAPI spec: api/openapi.yaml

Observability

Start the containerized service (URL Shortener + Prometheus + Grafana):

docker compose up

• App: http://localhost:8080 (metrics at http://localhost:8080/metrics)
• Prometheus: http://localhost:9090
• Grafana: http://localhost:3000 (admin/admin)

Tests

Run unit tests:

go test ./...

Run integration (black-box) tests:

go test -tags=integration ./...