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- package filenotify
- import (
- "errors"
- "fmt"
- "os"
- "sync"
- "time"
- "github.com/Sirupsen/logrus"
- "github.com/fsnotify/fsnotify"
- )
- var (
- // errPollerClosed is returned when the poller is closed
- errPollerClosed = errors.New("poller is closed")
- // errNoSuchWatch is returned when trying to remove a watch that doesn't exist
- errNoSuchWatch = errors.New("watch does not exist")
- )
- // watchWaitTime is the time to wait between file poll loops
- const watchWaitTime = 200 * time.Millisecond
- // filePoller is used to poll files for changes, especially in cases where fsnotify
- // can't be run (e.g. when inotify handles are exhausted)
- // filePoller satisfies the FileWatcher interface
- type filePoller struct {
- // watches is the list of files currently being polled, close the associated channel to stop the watch
- watches map[string]chan struct{}
- // events is the channel to listen to for watch events
- events chan fsnotify.Event
- // errors is the channel to listen to for watch errors
- errors chan error
- // mu locks the poller for modification
- mu sync.Mutex
- // closed is used to specify when the poller has already closed
- closed bool
- }
- // Add adds a filename to the list of watches
- // once added the file is polled for changes in a separate goroutine
- func (w *filePoller) Add(name string) error {
- w.mu.Lock()
- defer w.mu.Unlock()
- if w.closed {
- return errPollerClosed
- }
- f, err := os.Open(name)
- if err != nil {
- return err
- }
- fi, err := os.Stat(name)
- if err != nil {
- return err
- }
- if w.watches == nil {
- w.watches = make(map[string]chan struct{})
- }
- if _, exists := w.watches[name]; exists {
- return fmt.Errorf("watch exists")
- }
- chClose := make(chan struct{})
- w.watches[name] = chClose
- go w.watch(f, fi, chClose)
- return nil
- }
- // Remove stops and removes watch with the specified name
- func (w *filePoller) Remove(name string) error {
- w.mu.Lock()
- defer w.mu.Unlock()
- return w.remove(name)
- }
- func (w *filePoller) remove(name string) error {
- if w.closed {
- return errPollerClosed
- }
- chClose, exists := w.watches[name]
- if !exists {
- return errNoSuchWatch
- }
- close(chClose)
- delete(w.watches, name)
- return nil
- }
- // Events returns the event channel
- // This is used for notifications on events about watched files
- func (w *filePoller) Events() <-chan fsnotify.Event {
- return w.events
- }
- // Errors returns the errors channel
- // This is used for notifications about errors on watched files
- func (w *filePoller) Errors() <-chan error {
- return w.errors
- }
- // Close closes the poller
- // All watches are stopped, removed, and the poller cannot be added to
- func (w *filePoller) Close() error {
- w.mu.Lock()
- defer w.mu.Unlock()
- if w.closed {
- return nil
- }
- w.closed = true
- for name := range w.watches {
- w.remove(name)
- delete(w.watches, name)
- }
- return nil
- }
- // sendEvent publishes the specified event to the events channel
- func (w *filePoller) sendEvent(e fsnotify.Event, chClose <-chan struct{}) error {
- select {
- case w.events <- e:
- case <-chClose:
- return fmt.Errorf("closed")
- }
- return nil
- }
- // sendErr publishes the specified error to the errors channel
- func (w *filePoller) sendErr(e error, chClose <-chan struct{}) error {
- select {
- case w.errors <- e:
- case <-chClose:
- return fmt.Errorf("closed")
- }
- return nil
- }
- // watch is responsible for polling the specified file for changes
- // upon finding changes to a file or errors, sendEvent/sendErr is called
- func (w *filePoller) watch(f *os.File, lastFi os.FileInfo, chClose chan struct{}) {
- defer f.Close()
- for {
- time.Sleep(watchWaitTime)
- select {
- case <-chClose:
- logrus.Debugf("watch for %s closed", f.Name())
- return
- default:
- }
- fi, err := os.Stat(f.Name())
- if err != nil {
- // if we got an error here and lastFi is not set, we can presume that nothing has changed
- // This should be safe since before `watch()` is called, a stat is performed, there is any error `watch` is not called
- if lastFi == nil {
- continue
- }
- // If it doesn't exist at this point, it must have been removed
- // no need to send the error here since this is a valid operation
- if os.IsNotExist(err) {
- if err := w.sendEvent(fsnotify.Event{Op: fsnotify.Remove, Name: f.Name()}, chClose); err != nil {
- return
- }
- lastFi = nil
- continue
- }
- // at this point, send the error
- if err := w.sendErr(err, chClose); err != nil {
- return
- }
- continue
- }
- if lastFi == nil {
- if err := w.sendEvent(fsnotify.Event{Op: fsnotify.Create, Name: fi.Name()}, chClose); err != nil {
- return
- }
- lastFi = fi
- continue
- }
- if fi.Mode() != lastFi.Mode() {
- if err := w.sendEvent(fsnotify.Event{Op: fsnotify.Chmod, Name: fi.Name()}, chClose); err != nil {
- return
- }
- lastFi = fi
- continue
- }
- if fi.ModTime() != lastFi.ModTime() || fi.Size() != lastFi.Size() {
- if err := w.sendEvent(fsnotify.Event{Op: fsnotify.Write, Name: fi.Name()}, chClose); err != nil {
- return
- }
- lastFi = fi
- continue
- }
- }
- }
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