terraform/vendor/github.com/hpcloud/tail/watch/inotify_tracker.go

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2016-10-24 08:15:30 +02:00
// Copyright (c) 2015 HPE Software Inc. All rights reserved.
// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
package watch
import (
"log"
"os"
"path/filepath"
"sync"
"syscall"
"github.com/hpcloud/tail/util"
"gopkg.in/fsnotify.v1"
)
type InotifyTracker struct {
mux sync.Mutex
watcher *fsnotify.Watcher
chans map[string]chan fsnotify.Event
done map[string]chan bool
watchNums map[string]int
watch chan *watchInfo
remove chan *watchInfo
error chan error
}
type watchInfo struct {
op fsnotify.Op
fname string
}
func (this *watchInfo) isCreate() bool {
return this.op == fsnotify.Create
}
var (
// globally shared InotifyTracker; ensures only one fsnotify.Watcher is used
shared *InotifyTracker
// these are used to ensure the shared InotifyTracker is run exactly once
once = sync.Once{}
goRun = func() {
shared = &InotifyTracker{
mux: sync.Mutex{},
chans: make(map[string]chan fsnotify.Event),
done: make(map[string]chan bool),
watchNums: make(map[string]int),
watch: make(chan *watchInfo),
remove: make(chan *watchInfo),
error: make(chan error),
}
go shared.run()
}
logger = log.New(os.Stderr, "", log.LstdFlags)
)
// Watch signals the run goroutine to begin watching the input filename
func Watch(fname string) error {
return watch(&watchInfo{
fname: fname,
})
}
// Watch create signals the run goroutine to begin watching the input filename
// if call the WatchCreate function, don't call the Cleanup, call the RemoveWatchCreate
func WatchCreate(fname string) error {
return watch(&watchInfo{
op: fsnotify.Create,
fname: fname,
})
}
func watch(winfo *watchInfo) error {
// start running the shared InotifyTracker if not already running
once.Do(goRun)
winfo.fname = filepath.Clean(winfo.fname)
shared.watch <- winfo
return <-shared.error
}
// RemoveWatch signals the run goroutine to remove the watch for the input filename
func RemoveWatch(fname string) {
remove(&watchInfo{
fname: fname,
})
}
// RemoveWatch create signals the run goroutine to remove the watch for the input filename
func RemoveWatchCreate(fname string) {
remove(&watchInfo{
op: fsnotify.Create,
fname: fname,
})
}
func remove(winfo *watchInfo) {
// start running the shared InotifyTracker if not already running
once.Do(goRun)
winfo.fname = filepath.Clean(winfo.fname)
shared.mux.Lock()
done := shared.done[winfo.fname]
if done != nil {
delete(shared.done, winfo.fname)
close(done)
}
fname := winfo.fname
if winfo.isCreate() {
// Watch for new files to be created in the parent directory.
fname = filepath.Dir(fname)
}
shared.watchNums[fname]--
watchNum := shared.watchNums[fname]
if watchNum == 0 {
delete(shared.watchNums, fname)
}
shared.mux.Unlock()
// If we were the last ones to watch this file, unsubscribe from inotify.
// This needs to happen after releasing the lock because fsnotify waits
// synchronously for the kernel to acknowledge the removal of the watch
// for this file, which causes us to deadlock if we still held the lock.
if watchNum == 0 {
shared.watcher.Remove(fname)
}
shared.remove <- winfo
}
// Events returns a channel to which FileEvents corresponding to the input filename
// will be sent. This channel will be closed when removeWatch is called on this
// filename.
func Events(fname string) <-chan fsnotify.Event {
shared.mux.Lock()
defer shared.mux.Unlock()
return shared.chans[fname]
}
// Cleanup removes the watch for the input filename if necessary.
func Cleanup(fname string) {
RemoveWatch(fname)
}
// watchFlags calls fsnotify.WatchFlags for the input filename and flags, creating
// a new Watcher if the previous Watcher was closed.
func (shared *InotifyTracker) addWatch(winfo *watchInfo) error {
shared.mux.Lock()
defer shared.mux.Unlock()
if shared.chans[winfo.fname] == nil {
shared.chans[winfo.fname] = make(chan fsnotify.Event)
shared.done[winfo.fname] = make(chan bool)
}
fname := winfo.fname
if winfo.isCreate() {
// Watch for new files to be created in the parent directory.
fname = filepath.Dir(fname)
}
// already in inotify watch
if shared.watchNums[fname] > 0 {
shared.watchNums[fname]++
if winfo.isCreate() {
shared.watchNums[winfo.fname]++
}
return nil
}
err := shared.watcher.Add(fname)
if err == nil {
shared.watchNums[fname]++
if winfo.isCreate() {
shared.watchNums[winfo.fname]++
}
}
return err
}
// removeWatch calls fsnotify.RemoveWatch for the input filename and closes the
// corresponding events channel.
func (shared *InotifyTracker) removeWatch(winfo *watchInfo) {
shared.mux.Lock()
defer shared.mux.Unlock()
ch := shared.chans[winfo.fname]
if ch == nil {
return
}
delete(shared.chans, winfo.fname)
close(ch)
if !winfo.isCreate() {
return
}
shared.watchNums[winfo.fname]--
if shared.watchNums[winfo.fname] == 0 {
delete(shared.watchNums, winfo.fname)
}
}
// sendEvent sends the input event to the appropriate Tail.
func (shared *InotifyTracker) sendEvent(event fsnotify.Event) {
name := filepath.Clean(event.Name)
shared.mux.Lock()
ch := shared.chans[name]
done := shared.done[name]
shared.mux.Unlock()
if ch != nil && done != nil {
select {
case ch <- event:
case <-done:
}
}
}
// run starts the goroutine in which the shared struct reads events from its
// Watcher's Event channel and sends the events to the appropriate Tail.
func (shared *InotifyTracker) run() {
watcher, err := fsnotify.NewWatcher()
if err != nil {
util.Fatal("failed to create Watcher")
}
shared.watcher = watcher
for {
select {
case winfo := <-shared.watch:
shared.error <- shared.addWatch(winfo)
case winfo := <-shared.remove:
shared.removeWatch(winfo)
case event, open := <-shared.watcher.Events:
if !open {
return
}
shared.sendEvent(event)
case err, open := <-shared.watcher.Errors:
if !open {
return
} else if err != nil {
sysErr, ok := err.(*os.SyscallError)
if !ok || sysErr.Err != syscall.EINTR {
logger.Printf("Error in Watcher Error channel: %s", err)
}
}
}
}
}