[#3] metrics: Add gRPC middleware

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

metrics/grpc/client.go

@@ -0,0 +1,31 @@
+package grpc
+
+import (
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/metrics"
+	grpcprom "github.com/grpc-ecosystem/go-grpc-middleware/providers/prometheus"
+	"github.com/prometheus/client_golang/prometheus"
+	"google.golang.org/grpc"
+)
+
+var clientMetrics *grpcprom.ClientMetrics = grpcprom.NewClientMetrics(
+	grpcprom.WithClientHandlingTimeHistogram(
+		grpcprom.WithHistogramBuckets(prometheus.DefBuckets),
+	),
+	grpcprom.WithClientStreamRecvHistogram(
+		grpcprom.WithHistogramBuckets(prometheus.DefBuckets),
+	),
+)
+
+func init() {
+	metrics.Register(clientMetrics)
+}
+
+// NewUnaryClientInterceptor returns client interceptor to collect metrics from unary RPCs.
+func NewUnaryClientInterceptor() grpc.UnaryClientInterceptor {
+	return clientMetrics.UnaryClientInterceptor()
+}
+
+// NewStreamClientInterceptor returns client interceptor to collect metrics from stream RPCs.
+func NewStreamClientInterceptor() grpc.StreamClientInterceptor {
+	return clientMetrics.StreamClientInterceptor()
+}

metrics/grpc/server.go

@@ -0,0 +1,28 @@
+package grpc
+
+import (
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/metrics"
+	grpcprom "github.com/grpc-ecosystem/go-grpc-middleware/providers/prometheus"
+	"github.com/prometheus/client_golang/prometheus"
+	"google.golang.org/grpc"
+)
+
+var serverMetrics *grpcprom.ServerMetrics = grpcprom.NewServerMetrics(
+	grpcprom.WithServerHandlingTimeHistogram(
+		grpcprom.WithHistogramBuckets(prometheus.DefBuckets),
+	),
+)
+
+func init() {
+	metrics.Register(serverMetrics)
+}
+
+// NewUnaryServerInterceptor returns server interceptor to collect metrics from unary RPCs.
+func NewUnaryServerInterceptor() grpc.UnaryServerInterceptor {
+	return serverMetrics.UnaryServerInterceptor()
+}
+
+// NewStreamServerInterceptor returns server interceptor to collect metrics from stream RPCs.
+func NewStreamServerInterceptor() grpc.StreamServerInterceptor {
+	return serverMetrics.StreamServerInterceptor()
+}