diff --git a/vendor/google.golang.org/grpc/stats/stats.go b/vendor/google.golang.org/grpc/stats/stats.go
new file mode 100644
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+++ b/vendor/google.golang.org/grpc/stats/stats.go
@@ -0,0 +1,319 @@
+/*
+ *
+ * Copyright 2016 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 stats is for collecting and reporting various network and RPC stats.
+// This package is for monitoring purpose only. All fields are read-only.
+// All APIs are experimental.
+package stats // import "google.golang.org/grpc/stats"
+
+import (
+	"context"
+	"net"
+	"time"
+
+	"google.golang.org/grpc/metadata"
+)
+
+// RPCStats contains stats information about RPCs.
+type RPCStats interface {
+	isRPCStats()
+	// IsClient returns true if this RPCStats is from client side.
+	IsClient() bool
+}
+
+// Begin contains stats when an RPC attempt begins.
+// FailFast is only valid if this Begin is from client side.
+type Begin struct {
+	// Client is true if this Begin is from client side.
+	Client bool
+	// BeginTime is the time when the RPC attempt begins.
+	BeginTime time.Time
+	// FailFast indicates if this RPC is failfast.
+	FailFast bool
+	// IsClientStream indicates whether the RPC is a client streaming RPC.
+	IsClientStream bool
+	// IsServerStream indicates whether the RPC is a server streaming RPC.
+	IsServerStream bool
+	// IsTransparentRetryAttempt indicates whether this attempt was initiated
+	// due to transparently retrying a previous attempt.
+	IsTransparentRetryAttempt bool
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *Begin) IsClient() bool { return s.Client }
+
+func (s *Begin) isRPCStats() {}
+
+// InPayload contains the information for an incoming payload.
+type InPayload struct {
+	// Client is true if this InPayload is from client side.
+	Client bool
+	// Payload is the payload with original type.
+	Payload interface{}
+	// Data is the serialized message payload.
+	Data []byte
+	// Length is the length of uncompressed data.
+	Length int
+	// WireLength is the length of data on wire (compressed, signed, encrypted).
+	WireLength int
+	// RecvTime is the time when the payload is received.
+	RecvTime time.Time
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *InPayload) IsClient() bool { return s.Client }
+
+func (s *InPayload) isRPCStats() {}
+
+// InHeader contains stats when a header is received.
+type InHeader struct {
+	// Client is true if this InHeader is from client side.
+	Client bool
+	// WireLength is the wire length of header.
+	WireLength int
+	// Compression is the compression algorithm used for the RPC.
+	Compression string
+	// Header contains the header metadata received.
+	Header metadata.MD
+
+	// The following fields are valid only if Client is false.
+	// FullMethod is the full RPC method string, i.e., /package.service/method.
+	FullMethod string
+	// RemoteAddr is the remote address of the corresponding connection.
+	RemoteAddr net.Addr
+	// LocalAddr is the local address of the corresponding connection.
+	LocalAddr net.Addr
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *InHeader) IsClient() bool { return s.Client }
+
+func (s *InHeader) isRPCStats() {}
+
+// InTrailer contains stats when a trailer is received.
+type InTrailer struct {
+	// Client is true if this InTrailer is from client side.
+	Client bool
+	// WireLength is the wire length of trailer.
+	WireLength int
+	// Trailer contains the trailer metadata received from the server. This
+	// field is only valid if this InTrailer is from the client side.
+	Trailer metadata.MD
+}
+
+// IsClient indicates if the stats information is from client side.
+func (s *InTrailer) IsClient() bool { return s.Client }
+
+func (s *InTrailer) isRPCStats() {}
+
+// OutPayload contains the information for an outgoing payload.
+type OutPayload struct {
+	// Client is true if this OutPayload is from client side.
+	Client bool
+	// Payload is the payload with original type.
+	Payload interface{}
+	// Data is the serialized message payload.
+	Data []byte
+	// Length is the length of uncompressed data.
+	Length int
+	// WireLength is the length of data on wire (compressed, signed, encrypted).
+	WireLength int
+	// SentTime is the time when the payload is sent.
+	SentTime time.Time
+}
+
+// IsClient indicates if this stats information is from client side.
+func (s *OutPayload) IsClient() bool { return s.Client }
+
+func (s *OutPayload) isRPCStats() {}
+
+// OutHeader contains stats when a header is sent.
+type OutHeader struct {
+	// Client is true if this OutHeader is from client side.
+	Client bool
+	// Compression is the compression algorithm used for the RPC.
+	Compression string
+	// Header contains the header metadata sent.
+	Header metadata.MD
+
+	// The following fields are valid only if Client is true.
+	// FullMethod is the full RPC method string, i.e., /package.service/method.
+	FullMethod string
+	// RemoteAddr is the remote address of the corresponding connection.
+	RemoteAddr net.Addr
+	// LocalAddr is the local address of the corresponding connection.
+	LocalAddr net.Addr
+}
+
+// IsClient indicates if this stats information is from client side.
+func (s *OutHeader) IsClient() bool { return s.Client }
+
+func (s *OutHeader) isRPCStats() {}
+
+// OutTrailer contains stats when a trailer is sent.
+type OutTrailer struct {
+	// Client is true if this OutTrailer is from client side.
+	Client bool
+	// WireLength is the wire length of trailer.
+	//
+	// Deprecated: This field is never set. The length is not known when this message is
+	// emitted because the trailer fields are compressed with hpack after that.
+	WireLength int
+	// Trailer contains the trailer metadata sent to the client. This
+	// field is only valid if this OutTrailer is from the server side.
+	Trailer metadata.MD
+}
+
+// IsClient indicates if this stats information is from client side.
+func (s *OutTrailer) IsClient() bool { return s.Client }
+
+func (s *OutTrailer) isRPCStats() {}
+
+// End contains stats when an RPC ends.
+type End struct {
+	// Client is true if this End is from client side.
+	Client bool
+	// BeginTime is the time when the RPC began.
+	BeginTime time.Time
+	// EndTime is the time when the RPC ends.
+	EndTime time.Time
+	// Trailer contains the trailer metadata received from the server. This
+	// field is only valid if this End is from the client side.
+	// Deprecated: use Trailer in InTrailer instead.
+	Trailer metadata.MD
+	// Error is the error the RPC ended with. It is an error generated from
+	// status.Status and can be converted back to status.Status using
+	// status.FromError if non-nil.
+	Error error
+}
+
+// IsClient indicates if this is from client side.
+func (s *End) IsClient() bool { return s.Client }
+
+func (s *End) isRPCStats() {}
+
+// ConnStats contains stats information about connections.
+type ConnStats interface {
+	isConnStats()
+	// IsClient returns true if this ConnStats is from client side.
+	IsClient() bool
+}
+
+// ConnBegin contains the stats of a connection when it is established.
+type ConnBegin struct {
+	// Client is true if this ConnBegin is from client side.
+	Client bool
+}
+
+// IsClient indicates if this is from client side.
+func (s *ConnBegin) IsClient() bool { return s.Client }
+
+func (s *ConnBegin) isConnStats() {}
+
+// ConnEnd contains the stats of a connection when it ends.
+type ConnEnd struct {
+	// Client is true if this ConnEnd is from client side.
+	Client bool
+}
+
+// IsClient indicates if this is from client side.
+func (s *ConnEnd) IsClient() bool { return s.Client }
+
+func (s *ConnEnd) isConnStats() {}
+
+type incomingTagsKey struct{}
+type outgoingTagsKey struct{}
+
+// SetTags attaches stats tagging data to the context, which will be sent in
+// the outgoing RPC with the header grpc-tags-bin.  Subsequent calls to
+// SetTags will overwrite the values from earlier calls.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func SetTags(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, outgoingTagsKey{}, b)
+}
+
+// Tags returns the tags from the context for the inbound RPC.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func Tags(ctx context.Context) []byte {
+	b, _ := ctx.Value(incomingTagsKey{}).([]byte)
+	return b
+}
+
+// SetIncomingTags attaches stats tagging data to the context, to be read by
+// the application (not sent in outgoing RPCs).
+//
+// This is intended for gRPC-internal use ONLY.
+func SetIncomingTags(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, incomingTagsKey{}, b)
+}
+
+// OutgoingTags returns the tags from the context for the outbound RPC.
+//
+// This is intended for gRPC-internal use ONLY.
+func OutgoingTags(ctx context.Context) []byte {
+	b, _ := ctx.Value(outgoingTagsKey{}).([]byte)
+	return b
+}
+
+type incomingTraceKey struct{}
+type outgoingTraceKey struct{}
+
+// SetTrace attaches stats tagging data to the context, which will be sent in
+// the outgoing RPC with the header grpc-trace-bin.  Subsequent calls to
+// SetTrace will overwrite the values from earlier calls.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func SetTrace(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, outgoingTraceKey{}, b)
+}
+
+// Trace returns the trace from the context for the inbound RPC.
+//
+// NOTE: this is provided only for backward compatibility with existing clients
+// and will likely be removed in an upcoming release.  New uses should transmit
+// this type of data using metadata with a different, non-reserved (i.e. does
+// not begin with "grpc-") header name.
+func Trace(ctx context.Context) []byte {
+	b, _ := ctx.Value(incomingTraceKey{}).([]byte)
+	return b
+}
+
+// SetIncomingTrace attaches stats tagging data to the context, to be read by
+// the application (not sent in outgoing RPCs).  It is intended for
+// gRPC-internal use.
+func SetIncomingTrace(ctx context.Context, b []byte) context.Context {
+	return context.WithValue(ctx, incomingTraceKey{}, b)
+}
+
+// OutgoingTrace returns the trace from the context for the outbound RPC.  It is
+// intended for gRPC-internal use.
+func OutgoingTrace(ctx context.Context) []byte {
+	b, _ := ctx.Value(outgoingTraceKey{}).([]byte)
+	return b
+}