v3api, rpctypes: add ErrTimeoutDueToConnectionLost

Lack of GRPC code was causing this to look like a halting error to the client.

etcdserver/api/v3rpc/rpctypes/error.go

@@ -52,12 +52,13 @@ var (
 	ErrGRPCPermissionNotGranted = grpc.Errorf(codes.FailedPrecondition, "etcdserver: permission is not granted to the role")
 	ErrGRPCAuthNotEnabled       = grpc.Errorf(codes.FailedPrecondition, "etcdserver: authentication is not enabled")
 
-	ErrGRPCNoLeader               = grpc.Errorf(codes.Unavailable, "etcdserver: no leader")
-	ErrGRPCNotCapable             = grpc.Errorf(codes.Unavailable, "etcdserver: not capable")
-	ErrGRPCStopped                = grpc.Errorf(codes.Unavailable, "etcdserver: server stopped")
-	ErrGRPCTimeout                = grpc.Errorf(codes.Unavailable, "etcdserver: request timed out")
-	ErrGRPCTimeoutDueToLeaderFail = grpc.Errorf(codes.Unavailable, "etcdserver: request timed out, possibly due to previous leader failure")
-	ErrGRPCUnhealthy              = grpc.Errorf(codes.Unavailable, "etcdserver: unhealthy cluster")
+	ErrGRPCNoLeader                   = grpc.Errorf(codes.Unavailable, "etcdserver: no leader")
+	ErrGRPCNotCapable                 = grpc.Errorf(codes.Unavailable, "etcdserver: not capable")
+	ErrGRPCStopped                    = grpc.Errorf(codes.Unavailable, "etcdserver: server stopped")
+	ErrGRPCTimeout                    = grpc.Errorf(codes.Unavailable, "etcdserver: request timed out")
+	ErrGRPCTimeoutDueToLeaderFail     = grpc.Errorf(codes.Unavailable, "etcdserver: request timed out, possibly due to previous leader failure")
+	ErrGRPCTimeoutDueToConnectionLost = grpc.Errorf(codes.Unavailable, "etcdserver: request timed out, possibly due to connection lost")
+	ErrGRPCUnhealthy                  = grpc.Errorf(codes.Unavailable, "etcdserver: unhealthy cluster")
 
 	errStringToError = map[string]error{
 		grpc.ErrorDesc(ErrGRPCEmptyKey):     ErrGRPCEmptyKey,
@@ -91,12 +92,13 @@ var (
 		grpc.ErrorDesc(ErrGRPCPermissionNotGranted): ErrGRPCPermissionNotGranted,
 		grpc.ErrorDesc(ErrGRPCAuthNotEnabled):       ErrGRPCAuthNotEnabled,
 
-		grpc.ErrorDesc(ErrGRPCNoLeader):               ErrGRPCNoLeader,
-		grpc.ErrorDesc(ErrGRPCNotCapable):             ErrGRPCNotCapable,
-		grpc.ErrorDesc(ErrGRPCStopped):                ErrGRPCStopped,
-		grpc.ErrorDesc(ErrGRPCTimeout):                ErrGRPCTimeout,
-		grpc.ErrorDesc(ErrGRPCTimeoutDueToLeaderFail): ErrGRPCTimeoutDueToLeaderFail,
-		grpc.ErrorDesc(ErrGRPCUnhealthy):              ErrGRPCUnhealthy,
+		grpc.ErrorDesc(ErrGRPCNoLeader):                   ErrGRPCNoLeader,
+		grpc.ErrorDesc(ErrGRPCNotCapable):                 ErrGRPCNotCapable,
+		grpc.ErrorDesc(ErrGRPCStopped):                    ErrGRPCStopped,
+		grpc.ErrorDesc(ErrGRPCTimeout):                    ErrGRPCTimeout,
+		grpc.ErrorDesc(ErrGRPCTimeoutDueToLeaderFail):     ErrGRPCTimeoutDueToLeaderFail,
+		grpc.ErrorDesc(ErrGRPCTimeoutDueToConnectionLost): ErrGRPCTimeoutDueToConnectionLost,
+		grpc.ErrorDesc(ErrGRPCUnhealthy):                  ErrGRPCUnhealthy,
 	}
 
 	// client-side error
@@ -131,12 +133,13 @@ var (
 	ErrPermissionNotGranted = Error(ErrGRPCPermissionNotGranted)
 	ErrAuthNotEnabled       = Error(ErrGRPCAuthNotEnabled)
 
-	ErrNoLeader               = Error(ErrGRPCNoLeader)
-	ErrNotCapable             = Error(ErrGRPCNotCapable)
-	ErrStopped                = Error(ErrGRPCStopped)
-	ErrTimeout                = Error(ErrGRPCTimeout)
-	ErrTimeoutDueToLeaderFail = Error(ErrGRPCTimeoutDueToLeaderFail)
-	ErrUnhealthy              = Error(ErrGRPCUnhealthy)
+	ErrNoLeader                   = Error(ErrGRPCNoLeader)
+	ErrNotCapable                 = Error(ErrGRPCNotCapable)
+	ErrStopped                    = Error(ErrGRPCStopped)
+	ErrTimeout                    = Error(ErrGRPCTimeout)
+	ErrTimeoutDueToLeaderFail     = Error(ErrGRPCTimeoutDueToLeaderFail)
+	ErrTimeoutDueToConnectionLost = Error(ErrGRPCTimeoutDueToConnectionLost)
+	ErrUnhealthy                  = Error(ErrGRPCUnhealthy)
 )
 
 // EtcdError defines gRPC server errors.

etcdserver/api/v3rpc/util.go

@@ -57,6 +57,8 @@ func togRPCError(err error) error {
 		return rpctypes.ErrGRPCTimeout
 	case etcdserver.ErrTimeoutDueToLeaderFail:
 		return rpctypes.ErrGRPCTimeoutDueToLeaderFail
+	case etcdserver.ErrTimeoutDueToConnectionLost:
+		return rpctypes.ErrGRPCTimeoutDueToConnectionLost
 	case etcdserver.ErrUnhealthy:
 		return rpctypes.ErrGRPCUnhealthy