Inhaltsverzeichnis

Runbook: Prometheus

Runbook: Prometheus

Duration: ~15 minutes
Role: DevOps, SRE
Prerequisite: Prometheus Server, Gateway running

Collect metrics from Data Gateway with Prometheus.

Workflow

flowchart TD A[Start] --> B[Enable metrics] B --> C[Prometheus config] C --> D[Add scrape job] D --> E[Prometheus reload] E --> F[Check targets] F --> G{Up?} G -->|Yes| H[Done] G -->|No| I[Check firewall/endpoint] style H fill:#e8f5e9 style I fill:#ffebee

1. Enable Metrics in Gateway

appsettings.json:

{
  "Metrics": {
    "Enabled": true,
    "Endpoint": "/metrics"
  }
}

Or via NuGet (if not built-in):

# prometheus-net.AspNetCore
dotnet add package prometheus-net.AspNetCore

Program.cs:

// Metrics Middleware
app.UseHttpMetrics();
app.MapMetrics(); // /metrics Endpoint

2. Test Metrics Endpoint

curl http://localhost:5000/metrics
 
# Expected output (Prometheus format):
# HELP http_requests_total Total HTTP requests
# TYPE http_requests_total counter
# http_requests_total{method="GET",endpoint="/api/v1/dsn/demo/tables",status="200"} 42

3. Prometheus Configuration

/etc/prometheus/prometheus.yml:

global:
  scrape_interval: 15s
  evaluation_interval: 15s

scrape_configs:
  # Data Gateway
  - job_name: 'data-gateway'
    static_configs:
      - targets: ['gateway.example.com:5000']
    metrics_path: /metrics
    scheme: http  # or https
 
  # Multiple instances
  - job_name: 'data-gateway-cluster'
    static_configs:
      - targets:
          - 'gateway-1.example.com:5000'
          - 'gateway-2.example.com:5000'
          - 'gateway-3.example.com:5000'

4. Reload Prometheus

# Config reload (without restart)
curl -X POST http://localhost:9090/-/reload
 
# Or restart
sudo systemctl restart prometheus

5. Check Targets

Web UI: http://prometheus:9090/targets

Or via API:

curl -s http://localhost:9090/api/v1/targets | jq '.data.activeTargets[] | {job: .labels.job, health: .health}'

Expected output:

{
  "job": "data-gateway",
  "health": "up"
}

6. Important Queries

PromQL examples:

# Request rate (per second)
rate(http_requests_total{job="data-gateway"}[5m])

# Average response time
rate(http_request_duration_seconds_sum{job="data-gateway"}[5m])
/
rate(http_request_duration_seconds_count{job="data-gateway"}[5m])

# Error rate (5xx)
sum(rate(http_requests_total{job="data-gateway",status=~"5.."}[5m]))
/
sum(rate(http_requests_total{job="data-gateway"}[5m]))

# Memory usage
process_resident_memory_bytes{job="data-gateway"}

# Active connections
http_requests_in_progress{job="data-gateway"}

7. Checklist

#	Check	Done
—	——-	——
1	Metrics endpoint enabled	[ ]
2	/metrics reachable	[ ]
3	Prometheus config updated	[ ]
4	Prometheus reloaded	[ ]
5	Target „up“ in Prometheus	[ ]
6	Metrics visible in Grafana	[ ]

Troubleshooting

Problem	Cause	Solution
———	——-	———-
Target „down“	Endpoint not reachable	Check firewall, URL
`connection refused`	Gateway not running	Start Gateway
`404 Not Found`	Metrics not enabled	Check appsettings.json
No metrics	Wrong path	Check `metrics_path`

Kubernetes ServiceMonitor

For Prometheus Operator:

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: data-gateway
  namespace: monitoring
  labels:
    release: prometheus
spec:
  selector:
    matchLabels:
      app: data-gateway
  namespaceSelector:
    matchNames:
      - data-gateway
  endpoints:
    - port: http
      path: /metrics
      interval: 15s

Related Runbooks

Grafana Dashboard - Visualization
Alerting - Notifications
Kubernetes - K8s deployment

« <- Monitoring | -> Grafana Dashboard »

Wolfgang van der Stille @ EMSR DATA d.o.o. - Data Gateway Professional

operator, runbook, prometheus, metrics, monitoring