diff --git a/vendor/google.golang.org/grpc/connectivity/connectivity.go b/vendor/google.golang.org/grpc/connectivity/connectivity.go
new file mode 100644
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+++ b/vendor/google.golang.org/grpc/connectivity/connectivity.go
@@ -0,0 +1,94 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package connectivity defines connectivity semantics.
+// For details, see https://github.com/grpc/grpc/blob/master/doc/connectivity-semantics-and-api.md.
+package connectivity
+
+import (
+	"google.golang.org/grpc/grpclog"
+)
+
+var logger = grpclog.Component("core")
+
+// State indicates the state of connectivity.
+// It can be the state of a ClientConn or SubConn.
+type State int
+
+func (s State) String() string {
+	switch s {
+	case Idle:
+		return "IDLE"
+	case Connecting:
+		return "CONNECTING"
+	case Ready:
+		return "READY"
+	case TransientFailure:
+		return "TRANSIENT_FAILURE"
+	case Shutdown:
+		return "SHUTDOWN"
+	default:
+		logger.Errorf("unknown connectivity state: %d", s)
+		return "INVALID_STATE"
+	}
+}
+
+const (
+	// Idle indicates the ClientConn is idle.
+	Idle State = iota
+	// Connecting indicates the ClientConn is connecting.
+	Connecting
+	// Ready indicates the ClientConn is ready for work.
+	Ready
+	// TransientFailure indicates the ClientConn has seen a failure but expects to recover.
+	TransientFailure
+	// Shutdown indicates the ClientConn has started shutting down.
+	Shutdown
+)
+
+// ServingMode indicates the current mode of operation of the server.
+//
+// Only xDS enabled gRPC servers currently report their serving mode.
+type ServingMode int
+
+const (
+	// ServingModeStarting indicates that the server is starting up.
+	ServingModeStarting ServingMode = iota
+	// ServingModeServing indicates that the server contains all required
+	// configuration and is serving RPCs.
+	ServingModeServing
+	// ServingModeNotServing indicates that the server is not accepting new
+	// connections. Existing connections will be closed gracefully, allowing
+	// in-progress RPCs to complete. A server enters this mode when it does not
+	// contain the required configuration to serve RPCs.
+	ServingModeNotServing
+)
+
+func (s ServingMode) String() string {
+	switch s {
+	case ServingModeStarting:
+		return "STARTING"
+	case ServingModeServing:
+		return "SERVING"
+	case ServingModeNotServing:
+		return "NOT_SERVING"
+	default:
+		logger.Errorf("unknown serving mode: %d", s)
+		return "INVALID_MODE"
+	}
+}