Bump cAdvisor (and dependencies) godeps version

vendor/github.com/google/cadvisor/utils/tail/tail.go

@@ -0,0 +1,146 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// 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 tail implements "tail -F" functionality following rotated logs
+package tail
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+
+	"github.com/golang/glog"
+	"golang.org/x/exp/inotify"
+)
+
+type Tail struct {
+	reader     *bufio.Reader
+	readerErr  error
+	readerLock sync.RWMutex
+	filename   string
+	file       *os.File
+	stop       chan bool
+	watcher    *inotify.Watcher
+}
+
+const (
+	defaultRetryInterval = 100 * time.Millisecond
+	maxRetryInterval     = 30 * time.Second
+)
+
+// NewTail starts opens the given file and watches it for deletion/rotation
+func NewTail(filename string) (*Tail, error) {
+	t := &Tail{
+		filename: filename,
+	}
+	var err error
+	t.stop = make(chan bool)
+	t.watcher, err = inotify.NewWatcher()
+	if err != nil {
+		return nil, fmt.Errorf("inotify init failed on %s: %v", t.filename, err)
+	}
+	go t.watchLoop()
+	return t, nil
+}
+
+// Read implements the io.Reader interface for Tail
+func (t *Tail) Read(p []byte) (int, error) {
+	t.readerLock.RLock()
+	defer t.readerLock.RUnlock()
+	if t.reader == nil || t.readerErr != nil {
+		return 0, t.readerErr
+	}
+	return t.reader.Read(p)
+}
+
+var _ io.Reader = &Tail{}
+
+// Close stops watching and closes the file
+func (t *Tail) Close() {
+	close(t.stop)
+}
+
+func (t *Tail) attemptOpen() error {
+	t.readerLock.Lock()
+	defer t.readerLock.Unlock()
+	t.reader = nil
+	t.readerErr = nil
+	attempt := 0
+	for interval := defaultRetryInterval; ; interval *= 2 {
+		attempt++
+		glog.V(4).Infof("Opening %s (attempt %d)", t.filename, attempt)
+		var err error
+		t.file, err = os.Open(t.filename)
+		if err == nil {
+			// TODO: not interested in old events?
+			//t.file.Seek(0, os.SEEK_END)
+			t.reader = bufio.NewReader(t.file)
+			return nil
+		}
+		if interval >= maxRetryInterval {
+			break
+		}
+		select {
+		case <-time.After(interval):
+		case <-t.stop:
+			t.readerErr = io.EOF
+			return fmt.Errorf("watch was cancelled")
+		}
+	}
+	err := fmt.Errorf("can't open log file %s", t.filename)
+	t.readerErr = err
+	return err
+}
+
+func (t *Tail) watchLoop() {
+	for {
+		err := t.watchFile()
+		if err != nil {
+			glog.Errorf("Tail failed on %s: %v", t.filename, err)
+			break
+		}
+	}
+}
+
+func (t *Tail) watchFile() error {
+	err := t.attemptOpen()
+	if err != nil {
+		return err
+	}
+	defer t.file.Close()
+
+	watchDir := filepath.Dir(t.filename)
+	err = t.watcher.AddWatch(watchDir, inotify.IN_MOVED_FROM|inotify.IN_DELETE)
+	if err != nil {
+		return fmt.Errorf("Failed to add watch to directory %s: %v", watchDir, err)
+	}
+	defer t.watcher.RemoveWatch(watchDir)
+
+	for {
+		select {
+		case event := <-t.watcher.Event:
+			eventPath := filepath.Clean(event.Name) // Directory events have an extra '/'
+			if eventPath == t.filename {
+				glog.V(4).Infof("Log file %s moved/deleted", t.filename)
+				return nil
+			}
+		case <-t.stop:
+			return fmt.Errorf("watch was cancelled")
+		}
+	}
+}