From 6b51f0755f9f125ddd71465453d045bf7d9eba71 Mon Sep 17 00:00:00 2001
From: boreq <boreq@0x46.net>
Date: Wed, 22 Nov 2023 15:11:10 +0100
Subject: [PATCH] Add metrics for the number of stored events

---
 service/adapters/prometheus/prometheus.go     | 13 ++++++++
 service/adapters/sqlite/event_repository.go   | 11 +++++++
 .../adapters/sqlite/event_repository_test.go  | 33 +++++++++++++++++++
 service/app/app.go                            |  3 ++
 service/app/handler_update_metrics.go         |  6 ++++
 5 files changed, 66 insertions(+)

diff --git a/service/adapters/prometheus/prometheus.go b/service/adapters/prometheus/prometheus.go
index 1e184b0..c26e60c 100644
--- a/service/adapters/prometheus/prometheus.go
+++ b/service/adapters/prometheus/prometheus.go
@@ -44,6 +44,7 @@ type Prometheus struct {
 	relayConnectionReceivedMessagesCounter  *prometheus.CounterVec
 	relayConnectionDisconnectionsCounter    *prometheus.CounterVec
 	storedRelayAddressesGauge               prometheus.Gauge
+	storedEventsGauge                       prometheus.Gauge
 
 	registry *prometheus.Registry
 
@@ -126,6 +127,12 @@ func NewPrometheus(logger logging.Logger) (*Prometheus, error) {
 			Help: "Number of stored relay addresses.",
 		},
 	)
+	storedEventsGauge := prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Name: "stored_events_gauge",
+			Help: "Number of stored events.",
+		},
+	)
 
 	reg := prometheus.NewRegistry()
 	for _, v := range []prometheus.Collector{
@@ -140,6 +147,7 @@ func NewPrometheus(logger logging.Logger) (*Prometheus, error) {
 		relayConnectionReceivedMessagesCounter,
 		relayConnectionDisconnectionsCounter,
 		storedRelayAddressesGauge,
+		storedEventsGauge,
 		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
 		collectors.NewGoCollector(),
 	} {
@@ -173,6 +181,7 @@ func NewPrometheus(logger logging.Logger) (*Prometheus, error) {
 		relayConnectionReceivedMessagesCounter:  relayConnectionReceivedMessagesCounter,
 		relayConnectionDisconnectionsCounter:    relayConnectionDisconnectionsCounter,
 		storedRelayAddressesGauge:               storedRelayAddressesGauge,
+		storedEventsGauge:                       storedEventsGauge,
 
 		registry: reg,
 
@@ -234,6 +243,10 @@ func (p *Prometheus) ReportNumberOfStoredRelayAddresses(n int) {
 	p.storedRelayAddressesGauge.Set(float64(n))
 }
 
+func (p *Prometheus) ReportNumberOfStoredEvents(n int) {
+	p.storedEventsGauge.Set(float64(n))
+}
+
 func (p *Prometheus) Registry() *prometheus.Registry {
 	return p.registry
 }
diff --git a/service/adapters/sqlite/event_repository.go b/service/adapters/sqlite/event_repository.go
index f44c80e..f1af2f2 100644
--- a/service/adapters/sqlite/event_repository.go
+++ b/service/adapters/sqlite/event_repository.go
@@ -46,6 +46,17 @@ func (r *EventRepository) Get(ctx context.Context, eventID domain.EventId) (doma
 	return r.readEvent(result)
 }
 
+func (r *EventRepository) Count(ctx context.Context) (int, error) {
+	row := r.tx.QueryRow(`SELECT COUNT(*) FROM events`)
+
+	var count int
+	if err := row.Scan(&count); err != nil {
+		return 0, errors.Wrap(err, "error scanning")
+	}
+
+	return count, nil
+}
+
 func (m *EventRepository) readEvent(result *sql.Row) (domain.Event, error) {
 	var payload []byte
 
diff --git a/service/adapters/sqlite/event_repository_test.go b/service/adapters/sqlite/event_repository_test.go
index bdf89ef..e8f320a 100644
--- a/service/adapters/sqlite/event_repository_test.go
+++ b/service/adapters/sqlite/event_repository_test.go
@@ -69,3 +69,36 @@ func TestEventRepository_ItIsPossibleToSaveAndGetEvents(t *testing.T) {
 	})
 	require.NoError(t, err)
 }
+
+func TestEventRepository_CountCountsSavedEvents(t *testing.T) {
+	ctx := fixtures.TestContext(t)
+	adapters := NewTestAdapters(ctx, t)
+
+	err := adapters.TransactionProvider.Transact(ctx, func(ctx context.Context, adapters sqlite.TestAdapters) error {
+		n, err := adapters.EventRepository.Count(ctx)
+		require.NoError(t, err)
+		require.Equal(t, 0, n)
+
+		return nil
+	})
+	require.NoError(t, err)
+
+	for i := 0; i < 5; i++ {
+		err = adapters.TransactionProvider.Transact(ctx, func(ctx context.Context, adapters sqlite.TestAdapters) error {
+			err := adapters.EventRepository.Save(ctx, fixtures.SomeEvent())
+			require.NoError(t, err)
+
+			return nil
+		})
+		require.NoError(t, err)
+
+		err = adapters.TransactionProvider.Transact(ctx, func(ctx context.Context, adapters sqlite.TestAdapters) error {
+			n, err := adapters.EventRepository.Count(ctx)
+			require.NoError(t, err)
+			require.Equal(t, i+1, n)
+
+			return nil
+		})
+		require.NoError(t, err)
+	}
+}
diff --git a/service/app/app.go b/service/app/app.go
index fc686eb..de8269d 100644
--- a/service/app/app.go
+++ b/service/app/app.go
@@ -30,6 +30,8 @@ type EventRepository interface {
 
 	// Get returns ErrEventNotFound.
 	Get(ctx context.Context, eventID domain.EventId) (domain.Event, error)
+
+	Count(ctx context.Context) (int, error)
 }
 
 type RelayRepository interface {
@@ -96,6 +98,7 @@ type Metrics interface {
 	ReportReceivedEvent(address domain.RelayAddress)
 	ReportQueueLength(topic string, n int)
 	ReportNumberOfStoredRelayAddresses(n int)
+	ReportNumberOfStoredEvents(n int)
 }
 
 type ApplicationCall interface {
diff --git a/service/app/handler_update_metrics.go b/service/app/handler_update_metrics.go
index 7234e0a..afb4459 100644
--- a/service/app/handler_update_metrics.go
+++ b/service/app/handler_update_metrics.go
@@ -44,6 +44,12 @@ func (h *UpdateMetricsHandler) Handle(ctx context.Context) (err error) {
 		}
 		h.metrics.ReportNumberOfStoredRelayAddresses(n)
 
+		n, err = adapters.Events.Count(ctx)
+		if err != nil {
+			return errors.Wrap(err, "error counting events")
+		}
+		h.metrics.ReportNumberOfStoredEvents(n)
+
 		return nil
 	}); err != nil {
 		return errors.Wrap(err, "transaction error")