praefect: Wire up transaction metrics

Now that the transaction manager has a set of metrics, we need to wire
them up in Praefect. Let's do so.

2 files changed, 43 insertions, 1 deletions

diff --git a/cmd/praefect/main.go b/cmd/praefect/main.go
index 009734f0d..19d5e25fa 100644
--- a/cmd/praefect/main.go
+++ b/cmd/praefect/main.go
@@ -237,7 +237,20 @@ func run(cfgs []starter.Config, conf config.Config) error {
 	}
 	nodeManager.Start(1*time.Second, 3*time.Second)
 
-	transactionManager := transactions.NewManager()
+	transactionCounterMetric, err := metrics.RegisterTransactionCounter()
+	if err != nil {
+		return err
+	}
+
+	transactionDelayMetric, err := metrics.RegisterTransactionDelay(conf.Prometheus)
+	if err != nil {
+		return err
+	}
+
+	transactionManager := transactions.NewManager(
+		transactions.WithCounterMetric(transactionCounterMetric),
+		transactions.WithDelayMetric(transactionDelayMetric),
+	)
 
 	registry := protoregistry.New()
 	if err = registry.RegisterFiles(protoregistry.GitalyProtoFileDescriptors...); err != nil {
diff --git a/internal/praefect/metrics/prometheus.go b/internal/praefect/metrics/prometheus.go
index 48ac91708..f49dfb9ba 100644
--- a/internal/praefect/metrics/prometheus.go
+++ b/internal/praefect/metrics/prometheus.go
@@ -66,6 +66,35 @@ func RegisterReplicationJobsInFlight() (metrics.Gauge, error) {
 	return replicationJobsInFlight, prometheus.Register(replicationJobsInFlight)
 }
 
+// RegisterTransactionCounter creates and registers a Prometheus counter to
+// track the number of transactions and their outcomes.
+func RegisterTransactionCounter() (*prometheus.CounterVec, error) {
+	transactionCounter := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: "gitaly",
+			Subsystem: "praefect",
+			Name:      "transactions_total",
+		},
+		[]string{"action"},
+	)
+	return transactionCounter, prometheus.Register(transactionCounter)
+}
+
+// RegisterTransactionDelay creates and registers a Prometheus histogram to
+// track the delay of actions performed on transactions.
+func RegisterTransactionDelay(conf promconfig.Config) (metrics.HistogramVec, error) {
+	transactionDelay := prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: "gitaly",
+			Subsystem: "praefect",
+			Name:      "transactions_delay_seconds",
+			Buckets:   conf.GRPCLatencyBuckets,
+		},
+		[]string{"action"},
+	)
+	return transactionDelay, prometheus.Register(transactionDelay)
+}
+
 var MethodTypeCounter = prometheus.NewCounterVec(
 	prometheus.CounterOpts{
 		Namespace: "gitaly",