Go in cloud and DevOps: Kubernetes, Terraform and Prometheus

mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusOK) // "the process is alive"
})
mux.HandleFunc("GET /readyz", func(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), time.Second)
	defer cancel()
	if err := db.PingContext(ctx); err != nil {
		http.Error(w, "db not ready", http.StatusServiceUnavailable)
		return
	}
	w.WriteHeader(http.StatusOK) // "send me traffic"
})

import (
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var ordersTotal = promauto.NewCounterVec(prometheus.CounterOpts{
	Name: "orders_total",
	Help: "Orders placed, by result.",
}, []string{"result"})

// in a handler:
ordersTotal.WithLabelValues("success").Inc()

// expose for Prometheus to scrape:
mux.Handle("GET /metrics", promhttp.Handler())

apiVersion: apps/v1
kind: Deployment
metadata:
  name: expense-api
spec:
  replicas: 3
  selector:
    matchLabels:
      app: expense-api
  template:
    metadata:
      labels:
        app: expense-api
    spec:
      containers:
        - name: api
          image: registry.example.com/expense-api:1.0.0
          ports:
            - containerPort: 8080
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: expense-db
                  key: url
            - name: GOMEMLIMIT
              value: "100MiB"
          livenessProbe:
            httpGet: { path: /healthz, port: 8080 }
          readinessProbe:
            httpGet: { path: /readyz, port: 8080 }
          resources:
            requests: { cpu: 100m, memory: 64Mi }
            limits: { memory: 128Mi }

// sketch using k8s.io/client-go (needs a kubeconfig or in-cluster config)
pods, err := clientset.CoreV1().Pods("default").List(ctx, metav1.ListOptions{})
if err != nil {
	return err
}
for _, p := range pods.Items {
	fmt.Println(p.Name, p.Status.Phase)
}