Add grpc prometheus metrics

This provideds generic grpc metrics via prometheus

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

vendor/github.com/grpc-ecosystem/go-grpc-prometheus/server.go

@@ -0,0 +1,74 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+// gRPC Prometheus monitoring interceptors for server-side gRPC.
+
+package grpc_prometheus
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+)
+
+// PreregisterServices takes a gRPC server and pre-initializes all counters to 0.
+// This allows for easier monitoring in Prometheus (no missing metrics), and should be called *after* all services have
+// been registered with the server.
+func Register(server *grpc.Server) {
+	serviceInfo := server.GetServiceInfo()
+	for serviceName, info := range serviceInfo {
+		for _, mInfo := range info.Methods {
+			preRegisterMethod(serviceName, &mInfo)
+		}
+	}
+}
+
+// UnaryServerInterceptor is a gRPC server-side interceptor that provides Prometheus monitoring for Unary RPCs.
+func UnaryServerInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+	monitor := newServerReporter(Unary, info.FullMethod)
+	monitor.ReceivedMessage()
+	resp, err := handler(ctx, req)
+	monitor.Handled(grpc.Code(err))
+	if err == nil {
+		monitor.SentMessage()
+	}
+	return resp, err
+}
+
+// StreamServerInterceptor is a gRPC server-side interceptor that provides Prometheus monitoring for Streaming RPCs.
+func StreamServerInterceptor(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+	monitor := newServerReporter(streamRpcType(info), info.FullMethod)
+	err := handler(srv, &monitoredServerStream{ss, monitor})
+	monitor.Handled(grpc.Code(err))
+	return err
+}
+
+func streamRpcType(info *grpc.StreamServerInfo) grpcType {
+	if info.IsClientStream && !info.IsServerStream {
+		return ClientStream
+	} else if !info.IsClientStream && info.IsServerStream {
+		return ServerStream
+	}
+	return BidiStream
+}
+
+// monitoredStream wraps grpc.ServerStream allowing each Sent/Recv of message to increment counters.
+type monitoredServerStream struct {
+	grpc.ServerStream
+	monitor *serverReporter
+}
+
+func (s *monitoredServerStream) SendMsg(m interface{}) error {
+	err := s.ServerStream.SendMsg(m)
+	if err == nil {
+		s.monitor.SentMessage()
+	}
+	return err
+}
+
+func (s *monitoredServerStream) RecvMsg(m interface{}) error {
+	err := s.ServerStream.RecvMsg(m)
+	if err == nil {
+		s.monitor.ReceivedMessage()
+	}
+	return err
+}