feat: Add active users prometheus metric (#3406)

This  allows deployments using our Prometheus export t determine
the number of active users in the past hour.

The interval is an hour to align with API key last used refresh times.

SSH connections poll to check shutdown time, so this will be accurate
even on long-running connections without dashboard requests.

coderd/coderd.go

@@ -16,6 +16,7 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/klauspost/compress/zstd"
 	"github.com/pion/webrtc/v3"
+	"github.com/prometheus/client_golang/prometheus"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	"golang.org/x/xerrors"
 	"google.golang.org/api/idtoken"
@@ -58,6 +59,7 @@ type Options struct {
 	GoogleTokenValidator *idtoken.Validator
 	GithubOAuth2Config   *GithubOAuth2Config
 	OIDCConfig           *OIDCConfig
+	PrometheusRegistry   *prometheus.Registry
 	ICEServers           []webrtc.ICEServer
 	SecureAuthCookie     bool
 	SSHKeygenAlgorithm   gitsshkey.Algorithm
@@ -87,6 +89,9 @@ func New(options *Options) *API {
 			panic(xerrors.Errorf("rego authorize panic: %w", err))
 		}
 	}
+	if options.PrometheusRegistry == nil {
+		options.PrometheusRegistry = prometheus.NewRegistry()
+	}
 
 	siteCacheDir := options.CacheDir
 	if siteCacheDir != "" {
@@ -116,7 +121,7 @@ func New(options *Options) *API {
 				next.ServeHTTP(middleware.NewWrapResponseWriter(w, r.ProtoMajor), r)
 			})
 		},
-		httpmw.Prometheus,
+		httpmw.Prometheus(options.PrometheusRegistry),
 		tracing.HTTPMW(api.TracerProvider, "coderd.http"),
 	)
 

coderd/httpmw/prometheus.go

@@ -12,26 +12,31 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
-var (
-	requestsProcessed = promauto.NewCounterVec(prometheus.CounterOpts{
+func durationToFloatMs(d time.Duration) float64 {
+	return float64(d.Milliseconds())
+}
+
+func Prometheus(register prometheus.Registerer) func(http.Handler) http.Handler {
+	factory := promauto.With(register)
+	requestsProcessed := factory.NewCounterVec(prometheus.CounterOpts{
 		Namespace: "coderd",
 		Subsystem: "api",
 		Name:      "requests_processed_total",
 		Help:      "The total number of processed API requests",
 	}, []string{"code", "method", "path"})
-	requestsConcurrent = promauto.NewGauge(prometheus.GaugeOpts{
+	requestsConcurrent := factory.NewGauge(prometheus.GaugeOpts{
 		Namespace: "coderd",
 		Subsystem: "api",
 		Name:      "concurrent_requests",
 		Help:      "The number of concurrent API requests",
 	})
-	websocketsConcurrent = promauto.NewGauge(prometheus.GaugeOpts{
+	websocketsConcurrent := factory.NewGauge(prometheus.GaugeOpts{
 		Namespace: "coderd",
 		Subsystem: "api",
 		Name:      "concurrent_websockets",
 		Help:      "The total number of concurrent API websockets",
 	})
-	websocketsDist = promauto.NewHistogramVec(prometheus.HistogramOpts{
+	websocketsDist := factory.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace: "coderd",
 		Subsystem: "api",
 		Name:      "websocket_durations_ms",
@@ -45,58 +50,55 @@ var (
 			durationToFloatMs(30 * time.Hour),
 		},
 	}, []string{"path"})
-	requestsDist = promauto.NewHistogramVec(prometheus.HistogramOpts{
+	requestsDist := factory.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace: "coderd",
 		Subsystem: "api",
 		Name:      "request_latencies_ms",
 		Help:      "Latency distribution of requests in milliseconds",
 		Buckets:   []float64{1, 5, 10, 25, 50, 100, 500, 1000, 5000, 10000, 30000},
 	}, []string{"method", "path"})
-)
 
-func durationToFloatMs(d time.Duration) float64 {
-	return float64(d.Milliseconds())
-}
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			var (
+				start  = time.Now()
+				method = r.Method
+				rctx   = chi.RouteContext(r.Context())
+			)
 
-func Prometheus(next http.Handler) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		var (
-			start  = time.Now()
-			method = r.Method
-			rctx   = chi.RouteContext(r.Context())
-		)
-		sw, ok := w.(chimw.WrapResponseWriter)
-		if !ok {
-			panic("dev error: http.ResponseWriter is not chimw.WrapResponseWriter")
-		}
+			sw, ok := w.(chimw.WrapResponseWriter)
+			if !ok {
+				panic("dev error: http.ResponseWriter is not chimw.WrapResponseWriter")
+			}
 
-		var (
-			dist     *prometheus.HistogramVec
-			distOpts []string
-		)
-		// We want to count websockets separately.
-		if isWebsocketUpgrade(r) {
-			websocketsConcurrent.Inc()
-			defer websocketsConcurrent.Dec()
+			var (
+				dist     *prometheus.HistogramVec
+				distOpts []string
+			)
+			// We want to count WebSockets separately.
+			if isWebsocketUpgrade(r) {
+				websocketsConcurrent.Inc()
+				defer websocketsConcurrent.Dec()
 
-			dist = websocketsDist
-		} else {
-			requestsConcurrent.Inc()
-			defer requestsConcurrent.Dec()
+				dist = websocketsDist
+			} else {
+				requestsConcurrent.Inc()
+				defer requestsConcurrent.Dec()
 
-			dist = requestsDist
-			distOpts = []string{method}
-		}
+				dist = requestsDist
+				distOpts = []string{method}
+			}
 
-		next.ServeHTTP(w, r)
+			next.ServeHTTP(w, r)
 
-		path := rctx.RoutePattern()
-		distOpts = append(distOpts, path)
-		statusStr := strconv.Itoa(sw.Status())
+			path := rctx.RoutePattern()
+			distOpts = append(distOpts, path)
+			statusStr := strconv.Itoa(sw.Status())
 
-		requestsProcessed.WithLabelValues(statusStr, method, path).Inc()
-		dist.WithLabelValues(distOpts...).Observe(float64(time.Since(start)) / 1e6)
-	})
+			requestsProcessed.WithLabelValues(statusStr, method, path).Inc()
+			dist.WithLabelValues(distOpts...).Observe(float64(time.Since(start)) / 1e6)
+		})
+	}
 }
 
 func isWebsocketUpgrade(r *http.Request) bool {

coderd/httpmw/prometheus_test.go

@@ -0,0 +1,31 @@
+package httpmw_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/go-chi/chi/v5"
+	chimw "github.com/go-chi/chi/v5/middleware"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/coderd/httpmw"
+)
+
+func TestPrometheus(t *testing.T) {
+	t.Parallel()
+	t.Run("All", func(t *testing.T) {
+		req := httptest.NewRequest("GET", "/", nil)
+		req = req.WithContext(context.WithValue(req.Context(), chi.RouteCtxKey, chi.NewRouteContext()))
+		res := chimw.NewWrapResponseWriter(httptest.NewRecorder(), 0)
+		reg := prometheus.NewRegistry()
+		httpmw.Prometheus(reg)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusOK)
+		})).ServeHTTP(res, req)
+		metrics, err := reg.Gather()
+		require.NoError(t, err)
+		require.Greater(t, len(metrics), 0)
+	})
+}

coderd/prometheusmetrics/prometheusmetrics.go

@@ -0,0 +1,52 @@
+package prometheusmetrics
+
+import (
+	"context"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/coder/coder/coderd/database"
+)
+
+// ActiveUsers tracks the number of users that have authenticated within the past hour.
+func ActiveUsers(ctx context.Context, registerer prometheus.Registerer, db database.Store, duration time.Duration) (context.CancelFunc, error) {
+	if duration == 0 {
+		duration = 5 * time.Minute
+	}
+
+	gauge := prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "coderd",
+		Subsystem: "api",
+		Name:      "active_users_duration_hour",
+		Help:      "The number of users that have been active within the last hour.",
+	})
+	err := registerer.Register(gauge)
+	if err != nil {
+		return nil, err
+	}
+
+	ctx, cancelFunc := context.WithCancel(ctx)
+	ticker := time.NewTicker(duration)
+	go func() {
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+			}
+			apiKeys, err := db.GetAPIKeysLastUsedAfter(ctx, database.Now().Add(-1*time.Hour))
+			if err != nil {
+				continue
+			}
+			distinctUsers := map[uuid.UUID]struct{}{}
+			for _, apiKey := range apiKeys {
+				distinctUsers[apiKey.UserID] = struct{}{}
+			}
+			gauge.Set(float64(len(distinctUsers)))
+		}
+	}()
+	return cancelFunc, nil
+}

coderd/prometheusmetrics/prometheusmetrics_test.go

@@ -0,0 +1,93 @@
+package prometheusmetrics_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/coderd/database"
+	"github.com/coder/coder/coderd/database/databasefake"
+	"github.com/coder/coder/coderd/prometheusmetrics"
+	"github.com/coder/coder/testutil"
+)
+
+func TestActiveUsers(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range []struct {
+		Name     string
+		Database func() database.Store
+		Count    int
+	}{{
+		Name: "None",
+		Database: func() database.Store {
+			return databasefake.New()
+		},
+		Count: 0,
+	}, {
+		Name: "One",
+		Database: func() database.Store {
+			db := databasefake.New()
+			_, _ = db.InsertAPIKey(context.Background(), database.InsertAPIKeyParams{
+				UserID:   uuid.New(),
+				LastUsed: database.Now(),
+			})
+			return db
+		},
+		Count: 1,
+	}, {
+		Name: "OneWithExpired",
+		Database: func() database.Store {
+			db := databasefake.New()
+			_, _ = db.InsertAPIKey(context.Background(), database.InsertAPIKeyParams{
+				UserID:   uuid.New(),
+				LastUsed: database.Now(),
+			})
+			// Because this API key hasn't been used in the past hour, this shouldn't
+			// add to the user count.
+			_, _ = db.InsertAPIKey(context.Background(), database.InsertAPIKeyParams{
+				UserID:   uuid.New(),
+				LastUsed: database.Now().Add(-2 * time.Hour),
+			})
+			return db
+		},
+		Count: 1,
+	}, {
+		Name: "Multiple",
+		Database: func() database.Store {
+			db := databasefake.New()
+			_, _ = db.InsertAPIKey(context.Background(), database.InsertAPIKeyParams{
+				UserID:   uuid.New(),
+				LastUsed: database.Now(),
+			})
+			_, _ = db.InsertAPIKey(context.Background(), database.InsertAPIKeyParams{
+				UserID:   uuid.New(),
+				LastUsed: database.Now(),
+			})
+			return db
+		},
+		Count: 2,
+	}} {
+		tc := tc
+		t.Run(tc.Name, func(t *testing.T) {
+			t.Parallel()
+			registry := prometheus.NewRegistry()
+			cancel, err := prometheusmetrics.ActiveUsers(context.Background(), registry, tc.Database(), time.Millisecond)
+			require.NoError(t, err)
+			t.Cleanup(cancel)
+
+			var result int
+			require.Eventually(t, func() bool {
+				metrics, err := registry.Gather()
+				assert.NoError(t, err)
+				result = int(*metrics[0].Metric[0].Gauge.Value)
+				return result == tc.Count
+			}, testutil.WaitShort, testutil.IntervalFast)
+		})
+	}
+}