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.NET API (Coderz REST API)

URL: http://109.199.120.120:5050 Technology: ASP.NET Core Database: PostgreSQL (coderz-db, port 5433) The .NET API is the primary backend service of the Coderz Stack. It serves as the main REST API, backed by PostgreSQL, with full Prometheus metrics exposure, structured logging to ELK, and load testing coverage via k6.

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Endpoints

MethodPathDescription
GET/api/itemsList all items (supports ?page=N)
GET/api/items/{id}Get a single item by ID
POST/api/itemsCreate a new item
PUT/api/items/{id}Update an item
DELETE/api/items/{id}Delete an item
GET/metricsPrometheus metrics endpoint
GET/healthHealth check endpoint

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Metrics Exposed to Prometheus

The .NET API uses the prometheus-net library to expose: 
http_requests_received_total        # Total request count by method, path, status
http_request_duration_seconds       # Request duration histogram
http_requests_in_progress           # Currently active requests
dotnet_collection_count_total       # Garbage collection counts
dotnet_total_memory_bytes           # .NET process memory
process_cpu_seconds_total           # CPU usage
These are scraped by Prometheus every 15 seconds and displayed in the .NET API Full Stack Grafana dashboard.

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Grafana Dashboard: .NET API Full Stack

PanelWhat It Shows
Request RateRequests per second, by endpoint
Error Rate4xx and 5xx responses per minute
Response TimeP50, P95, P99 latency percentiles
Active RequestsCurrently in-flight requests
PostgreSQL QueriesQuery count and duration
Live Request LogLive Loki log stream of every request

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Structured Log Format

Every request logs a structured JSON entry: 
{
  "@timestamp": "2026-03-06T20:15:33Z",
  "level": "INFO",
  "client.ip": "192.168.1.50",
  "http.method": "GET",
  "http.url.path": "/api/items",
  "http.url.query": "page=2",
  "http.response.status_code": 200,
  "duration_ms": 87,
  "db.query": "SELECT * FROM items LIMIT 20 OFFSET 20",
  "db.duration_ms": 34,
  "service.name": "coderz-dotnet-api"
}

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k6 Load Test Scenarios

ScenarioDescription
dotnet-itemsPaginated GET /api/items — simulates read traffic
dotnet-crudGET + POST + PUT cycle — simulates full CRUD
dotnet-mixedAll endpoints mixed — simulates realistic traffic
dotnet-stressStep ramp-up to find breaking point
Run from the k6 UI at http://109.199.120.120:9000.

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Database Connection

The .NET API connects to PostgreSQL with:
  • Host: coderz-db (Docker internal)
  • Port: 5433
  • Database: coderapi
  • User: coderapi
  • Password: coderapi_2024

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View Logs in Kibana

service.name: "coderz-dotnet-api"
Filter to errors only: 
service.name: "coderz-dotnet-api" and http.response.status_code >= 400