Added server health-check

backend/backend.go

@@ -36,6 +36,9 @@ type Backend interface {
 	// List iterates over done resources within a namespace
 	List(ctx context.Context, req *rpc.ListRequest, iter Iterator) error
 
+	// Ping pings the backend connection.
+	Ping() error
+
 	// Close closes the backend connection.
 	Close() error
 }

backend/mock/mock.go

@@ -133,6 +133,9 @@ func (b *Backend) List(_ context.Context, req *rpc.ListRequest, iter backend.Ite
 	return nil
 }
 
+// Ping implements the backend.Backend interface.
+func (*Backend) Ping() error { return nil }
+
 // Close implements the backend.Backend interface.
 func (*Backend) Close() error { return nil }
 

backend/postgres/postgres.go

@@ -214,6 +214,9 @@ func (b *postgres) Done(ctx context.Context, owner string, handleID uuid.UUID, m
 	return performUpdate(ctx, stmt)
 }
 
+// Ping implements the backend.Backend interface.
+func (b *postgres) Ping() error { return b.DB.Ping() }
+
 // Close implements the backend.Backend interface.
 func (b *postgres) Close() error {
 	if b.ownDB {

cmd/accord-server/main.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"net"
 	"strings"
+	"time"
 
 	"github.com/bsm/accord/backend/postgres"
 	"github.com/bsm/accord/internal/service"
@@ -45,8 +46,12 @@ func run(ctx context.Context) error {
 		return err
 	}
 
-	log.Printf("Listening on %s\n", flags.addr)
 	srv := grpc.NewServer()
-	rpc.RegisterV1Server(srv, service.New(backend))
+	svc := service.New(backend)
+	rpc.RegisterV1Server(srv, svc)
+	hch := rpc.RunHealthCheck(srv, svc, "accord", 5*time.Second)
+	defer hch.Stop()
+
+	log.Printf("Listening on %s\n", flags.addr)
 	return srv.Serve(lis)
 }

internal/service/service.go

@@ -12,17 +12,23 @@ import (
 	"google.golang.org/grpc/status"
 )
 
-type service struct {
+// Service instances serve GRPC requests.
+type Service struct {
 	b backend.Backend
 }
 
 // New initalizes a new service
-func New(b backend.Backend) rpc.V1Server {
-	return &service{b: b}
+func New(b backend.Backend) *Service {
+	return &Service{b: b}
+}
+
+// Ping implements rpc.Pinger.
+func (s *Service) Ping() error {
+	return s.b.Ping()
 }
 
 // Acquire implements rpc.V1Server.
-func (s *service) Acquire(ctx context.Context, req *rpc.AcquireRequest) (*rpc.AcquireResponse, error) {
+func (s *Service) Acquire(ctx context.Context, req *rpc.AcquireRequest) (*rpc.AcquireResponse, error) {
 	if req.Owner == "" {
 		return nil, status.Error(codes.InvalidArgument, "invalid owner")
 	}
@@ -46,7 +52,7 @@ func (s *service) Acquire(ctx context.Context, req *rpc.AcquireRequest) (*rpc.Ac
 }
 
 // Renew implements rpc.V1Server.
-func (s *service) Renew(ctx context.Context, req *rpc.RenewRequest) (*rpc.RenewResponse, error) {
+func (s *Service) Renew(ctx context.Context, req *rpc.RenewRequest) (*rpc.RenewResponse, error) {
 	if req.Owner == "" {
 		return nil, status.Error(codes.InvalidArgument, "invalid owner")
 	}
@@ -63,7 +69,7 @@ func (s *service) Renew(ctx context.Context, req *rpc.RenewRequest) (*rpc.RenewR
 }
 
 // Done implements rpc.V1Server.
-func (s *service) Done(ctx context.Context, req *rpc.DoneRequest) (*rpc.DoneResponse, error) {
+func (s *Service) Done(ctx context.Context, req *rpc.DoneRequest) (*rpc.DoneResponse, error) {
 	if req.Owner == "" {
 		return nil, status.Error(codes.InvalidArgument, "invalid owner")
 	}
@@ -80,7 +86,7 @@ func (s *service) Done(ctx context.Context, req *rpc.DoneRequest) (*rpc.DoneResp
 }
 
 // List implements rpc.V1Server.
-func (s *service) List(req *rpc.ListRequest, srv rpc.V1_ListServer) error {
+func (s *Service) List(req *rpc.ListRequest, srv rpc.V1_ListServer) error {
 	return s.b.List(srv.Context(), req, func(data *backend.HandleData) error {
 		return srv.Send(convertHandle(data))
 	})

internal/service/service_test.go

@@ -13,7 +13,8 @@ import (
 )
 
 var _ = Describe("V1Service", func() {
-	var subject rpc.V1Server
+	var subject *service.Service
+	var _ rpc.V1Server = subject
 	var backend *mock.Backend
 	var ctx = context.Background()
 	const owner = "THEOWNER"

rpc/health.go

@@ -0,0 +1,51 @@
+package rpc
+
+import (
+	context "context"
+	"time"
+
+	grpc "google.golang.org/grpc"
+	"google.golang.org/grpc/health"
+	hpb "google.golang.org/grpc/health/grpc_health_v1"
+)
+
+// Pinger servers can handle ping requests.
+type Pinger interface {
+	Ping() error
+}
+
+// HealthCheck instances can be stopped.
+type HealthCheck interface {
+	Stop()
+}
+
+type healthCheck struct{ cancel context.CancelFunc }
+
+func (h *healthCheck) Stop() { h.cancel() }
+
+// RunHealthCheck starts a standard grpc health check.
+func RunHealthCheck(s *grpc.Server, c Pinger, name string, interval time.Duration) HealthCheck {
+	svc := health.NewServer()
+	hpb.RegisterHealthServer(s, svc)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-ctx.Done():
+				svc.SetServingStatus(name, hpb.HealthCheckResponse_NOT_SERVING)
+				return
+			case <-ticker.C:
+				if err := c.Ping(); err == nil {
+					svc.SetServingStatus(name, hpb.HealthCheckResponse_SERVING)
+				} else {
+					svc.SetServingStatus(name, hpb.HealthCheckResponse_NOT_SERVING)
+				}
+			}
+		}
+	}()
+	return &healthCheck{cancel: cancel}
+}