metrics_test.go

package metrics

import (
	"context"
	"io"
	"net/http"
	"testing"

	"git.perx.ru/perxis/perxis-go/pkg/id"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func serveMetrics(t *testing.T) *http.Server {
	mux := http.NewServeMux()
	mux.Handle("/metrics", promhttp.Handler())
	srv := &http.Server{Addr: "localhost:30301", Handler: mux}
	go func() { srv.ListenAndServe() }()
	return srv
}

func TestMetrics_Example(t *testing.T) {
	ctx := context.Background()
	t.Run("Metrics do not allow dynamically assigned labels", func(t *testing.T) {
		m := prometheus.NewCounterVec(prometheus.CounterOpts{Name: "test_counter_" + id.GenerateNewID()}, nil)
		prometheus.MustRegister(m)
		assert.Panics(t, func() {
			m.With(prometheus.Labels{"a": "v_a1", "b": "v_b1"}).Inc()
		})
	})

	t.Run("Metrics allow dynamically assigned label values", func(t *testing.T) {
		srv := serveMetrics(t)
		defer srv.Shutdown(ctx)

		name := "test_counter_" + id.GenerateNewID()
		m := prometheus.NewCounterVec(prometheus.CounterOpts{Name: name}, []string{"a", "b"})
		prometheus.MustRegister(m)
		m.With(prometheus.Labels{"a": "v_a1", "b": "v_b1"}).Inc()

		resp, err := http.Get("http://localhost:30301/metrics")
		require.NoError(t, err)
		defer resp.Body.Close()
		b, err := io.ReadAll(resp.Body)
		require.NoError(t, err)
		// fmt.Println(string(b))
		assert.Contains(t, string(b), name+"{a=\"v_a1\",b=\"v_b1\"} 1")
	})

	t.Run("Metrics with constant label values", func(t *testing.T) {
		srv := serveMetrics(t)
		defer srv.Shutdown(ctx)

		name := "test_counter_" + id.GenerateNewID()
		m := prometheus.NewCounterVec(prometheus.CounterOpts{
			Namespace:   "test_namespace",
			Subsystem:   "test_subsystem",
			Name:        name,
			Help:        "Test Help",
			ConstLabels: prometheus.Labels{"const_1": "val_1"},
		}, []string{"a", "b"})
		prometheus.MustRegister(m)
		m.With(prometheus.Labels{"a": "v_a1", "b": "v_b1"}).Inc()

		resp, err := http.Get("http://localhost:30301/metrics")
		require.NoError(t, err)
		defer resp.Body.Close()
		b, err := io.ReadAll(resp.Body)
		require.NoError(t, err)
		// fmt.Println(string(b))
		assert.Contains(t, string(b), name+"{a=\"v_a1\",b=\"v_b1\",const_1=\"val_1\"} 1")
	})
}