diff --git a/vendor/google.golang.org/grpc/internal/binarylog/sink.go b/vendor/google.golang.org/grpc/internal/binarylog/sink.go
new file mode 100644
index 0000000..20d044f
--- /dev/null
+++ b/vendor/google.golang.org/grpc/internal/binarylog/sink.go
@@ -0,0 +1,162 @@
+/*
+ *
+ * Copyright 2018 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 binarylog
+
+import (
+	"bufio"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"sync"
+	"time"
+
+	"github.com/golang/protobuf/proto"
+	pb "google.golang.org/grpc/binarylog/grpc_binarylog_v1"
+	"google.golang.org/grpc/grpclog"
+)
+
+var (
+	defaultSink Sink = &noopSink{} // TODO(blog): change this default (file in /tmp).
+)
+
+// SetDefaultSink sets the sink where binary logs will be written to.
+//
+// Not thread safe. Only set during initialization.
+func SetDefaultSink(s Sink) {
+	if defaultSink != nil {
+		defaultSink.Close()
+	}
+	defaultSink = s
+}
+
+// Sink writes log entry into the binary log sink.
+type Sink interface {
+	// Write will be called to write the log entry into the sink.
+	//
+	// It should be thread-safe so it can be called in parallel.
+	Write(*pb.GrpcLogEntry) error
+	// Close will be called when the Sink is replaced by a new Sink.
+	Close() error
+}
+
+type noopSink struct{}
+
+func (ns *noopSink) Write(*pb.GrpcLogEntry) error { return nil }
+func (ns *noopSink) Close() error                 { return nil }
+
+// newWriterSink creates a binary log sink with the given writer.
+//
+// Write() marshalls the proto message and writes it to the given writer. Each
+// message is prefixed with a 4 byte big endian unsigned integer as the length.
+//
+// No buffer is done, Close() doesn't try to close the writer.
+func newWriterSink(w io.Writer) *writerSink {
+	return &writerSink{out: w}
+}
+
+type writerSink struct {
+	out io.Writer
+}
+
+func (ws *writerSink) Write(e *pb.GrpcLogEntry) error {
+	b, err := proto.Marshal(e)
+	if err != nil {
+		grpclog.Infof("binary logging: failed to marshal proto message: %v", err)
+	}
+	hdr := make([]byte, 4)
+	binary.BigEndian.PutUint32(hdr, uint32(len(b)))
+	if _, err := ws.out.Write(hdr); err != nil {
+		return err
+	}
+	if _, err := ws.out.Write(b); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (ws *writerSink) Close() error { return nil }
+
+type bufWriteCloserSink struct {
+	mu     sync.Mutex
+	closer io.Closer
+	out    *writerSink   // out is built on buf.
+	buf    *bufio.Writer // buf is kept for flush.
+
+	writeStartOnce sync.Once
+	writeTicker    *time.Ticker
+}
+
+func (fs *bufWriteCloserSink) Write(e *pb.GrpcLogEntry) error {
+	// Start the write loop when Write is called.
+	fs.writeStartOnce.Do(fs.startFlushGoroutine)
+	fs.mu.Lock()
+	if err := fs.out.Write(e); err != nil {
+		fs.mu.Unlock()
+		return err
+	}
+	fs.mu.Unlock()
+	return nil
+}
+
+const (
+	bufFlushDuration = 60 * time.Second
+)
+
+func (fs *bufWriteCloserSink) startFlushGoroutine() {
+	fs.writeTicker = time.NewTicker(bufFlushDuration)
+	go func() {
+		for range fs.writeTicker.C {
+			fs.mu.Lock()
+			fs.buf.Flush()
+			fs.mu.Unlock()
+		}
+	}()
+}
+
+func (fs *bufWriteCloserSink) Close() error {
+	if fs.writeTicker != nil {
+		fs.writeTicker.Stop()
+	}
+	fs.mu.Lock()
+	fs.buf.Flush()
+	fs.closer.Close()
+	fs.out.Close()
+	fs.mu.Unlock()
+	return nil
+}
+
+func newBufWriteCloserSink(o io.WriteCloser) Sink {
+	bufW := bufio.NewWriter(o)
+	return &bufWriteCloserSink{
+		closer: o,
+		out:    newWriterSink(bufW),
+		buf:    bufW,
+	}
+}
+
+// NewTempFileSink creates a temp file and returns a Sink that writes to this
+// file.
+func NewTempFileSink() (Sink, error) {
+	tempFile, err := ioutil.TempFile("/tmp", "grpcgo_binarylog_*.txt")
+	if err != nil {
+		return nil, fmt.Errorf("failed to create temp file: %v", err)
+	}
+	return newBufWriteCloserSink(tempFile), nil
+}