coder/coderd/x/nats/metrics_test.go

package nats_test

import (
	"context"
	"testing"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"github.com/coder/coder/v2/coderd/database/pubsub"
	"github.com/coder/coder/v2/coderd/x/nats"
	"github.com/coder/coder/v2/testutil"
)

func TestPubsub_Metrics(t *testing.T) {
	t.Parallel()

	ctx := testutil.Context(t, testutil.WaitLong)
	uut := newPubsub(t, nats.Options{})

	registry := prometheus.NewRegistry()
	err := registry.Register(uut)
	require.NoError(t, err)

	// each Gather measures pubsub latency by publishing a message & subscribing to it
	var gatherCount float64

	metrics, err := registry.Gather()
	gatherCount++
	require.NoError(t, err)
	require.True(t, testutil.PromGaugeHasValue(t, metrics, 0, "coder_nats_pubsub_current_events"))
	require.True(t, testutil.PromGaugeHasValue(t, metrics, 0, "coder_nats_pubsub_current_subscribers"))

	event := "test"
	data := "testing"
	messageChannel := make(chan []byte)
	unsub0, err := uut.Subscribe(event, func(_ context.Context, message []byte) {
		messageChannel <- message
	})
	require.NoError(t, err)
	go func() {
		err := uut.Publish(event, []byte(data))
		assert.NoError(t, err)
	}()
	_ = testutil.TryReceive(ctx, t, messageChannel)

	require.Eventually(t, func() bool {
		latencyBytes := gatherCount * pubsub.LatencyMessageLength
		metrics, err = registry.Gather()
		gatherCount++
		assert.NoError(t, err)
		return testutil.PromGaugeHasValue(t, metrics, 1, "coder_nats_pubsub_current_events") &&
			testutil.PromGaugeHasValue(t, metrics, 1, "coder_nats_pubsub_current_subscribers") &&
			testutil.PromGaugeHasValue(t, metrics, 1, "coder_nats_pubsub_connected") &&
			testutil.PromCounterHasValue(t, metrics, gatherCount, "coder_nats_pubsub_publishes_total", "true") &&
			testutil.PromCounterHasValue(t, metrics, gatherCount, "coder_nats_pubsub_subscribes_total", "true") &&
			testutil.PromCounterHasValue(t, metrics, gatherCount, "coder_nats_pubsub_messages_total", "normal") &&
			testutil.PromCounterHasValue(t, metrics, float64(len(data))+latencyBytes, "coder_nats_pubsub_received_bytes_total") &&
			testutil.PromCounterHasValue(t, metrics, float64(len(data))+latencyBytes, "coder_nats_pubsub_published_bytes_total") &&
			// The latency gauges can be exactly 0 on Windows, whose monotonic
			// clock advances in coarse (up to 15.6ms) ticks; a sub-tick publish
			// measures a zero duration. An absent gauge reads as -1, so >= 0
			// still proves the gauge was gathered, and the measures_total/errs
			// counters below prove measurement ran and succeeded.
			testutil.PromGaugeAssertion(t, metrics, func(in float64) bool { return in >= 0 }, "coder_nats_pubsub_send_latency_seconds") &&
			testutil.PromGaugeAssertion(t, metrics, func(in float64) bool { return in >= 0 }, "coder_nats_pubsub_receive_latency_seconds") &&
			testutil.PromCounterHasValue(t, metrics, gatherCount, "coder_nats_pubsub_latency_measures_total") &&
			!testutil.PromCounterGathered(t, metrics, "coder_nats_pubsub_latency_measure_errs_total")
	}, testutil.WaitShort, testutil.IntervalFast)

	colossalSize := 7600
	colossalData := make([]byte, colossalSize)
	for i := range colossalData {
		colossalData[i] = 'q'
	}
	unsub1, err := uut.Subscribe(event, func(_ context.Context, message []byte) {
		messageChannel <- message
	})
	require.NoError(t, err)
	go func() {
		err := uut.Publish(event, colossalData)
		assert.NoError(t, err)
	}()
	// should get 2 messages because we have 2 subs
	_ = testutil.TryReceive(ctx, t, messageChannel)
	_ = testutil.TryReceive(ctx, t, messageChannel)

	require.Eventually(t, func() bool {
		latencyBytes := gatherCount * pubsub.LatencyMessageLength
		metrics, err = registry.Gather()
		gatherCount++
		assert.NoError(t, err)
		return testutil.PromGaugeHasValue(t, metrics, 1, "coder_nats_pubsub_current_events") &&
			testutil.PromGaugeHasValue(t, metrics, 2, "coder_nats_pubsub_current_subscribers") &&
			testutil.PromGaugeHasValue(t, metrics, 1, "coder_nats_pubsub_connected") &&
			testutil.PromCounterHasValue(t, metrics, 1+gatherCount, "coder_nats_pubsub_publishes_total", "true") &&
			testutil.PromCounterHasValue(t, metrics, 1+gatherCount, "coder_nats_pubsub_subscribes_total", "true") &&
			testutil.PromCounterHasValue(t, metrics, gatherCount, "coder_nats_pubsub_messages_total", "normal") &&
			testutil.PromCounterHasValue(t, metrics, 1, "coder_nats_pubsub_messages_total", "colossal") &&
			testutil.PromCounterHasValue(t, metrics, float64(colossalSize+len(data))+latencyBytes, "coder_nats_pubsub_received_bytes_total") &&
			testutil.PromCounterHasValue(t, metrics, float64(colossalSize+len(data))+latencyBytes, "coder_nats_pubsub_published_bytes_total") &&
			// Zero latency is accepted for coarse clocks; see the comment on
			// the first Eventually above.
			testutil.PromGaugeAssertion(t, metrics, func(in float64) bool { return in >= 0 }, "coder_nats_pubsub_send_latency_seconds") &&
			testutil.PromGaugeAssertion(t, metrics, func(in float64) bool { return in >= 0 }, "coder_nats_pubsub_receive_latency_seconds") &&
			testutil.PromCounterHasValue(t, metrics, gatherCount, "coder_nats_pubsub_latency_measures_total") &&
			!testutil.PromCounterGathered(t, metrics, "coder_nats_pubsub_latency_measure_errs_total")
	}, testutil.WaitShort, testutil.IntervalFast)

	// Unsubscribing both local subscribers should decrement the
	// subscriber gauge back to 0, and removing the last subscriber on the
	// event should decrement the event gauge back to 0.
	unsub0()
	unsub1()

	require.Eventually(t, func() bool {
		metrics, err = registry.Gather()
		gatherCount++
		assert.NoError(t, err)
		return testutil.PromGaugeHasValue(t, metrics, 0, "coder_nats_pubsub_current_events") &&
			testutil.PromGaugeHasValue(t, metrics, 0, "coder_nats_pubsub_current_subscribers")
	}, testutil.WaitShort, testutil.IntervalFast)
}