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watcher.go
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watcher.go
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// +build go1.3,!plan9,!solaris
package main
import (
"log"
"os"
"path/filepath"
"time"
"gopkg.in/fsnotify.v1"
)
func WaitForReplacement(filename string, op fsnotify.Op,
watcher *fsnotify.Watcher) {
const sleep_interval = 50 * time.Millisecond
// Avoid a race when fsnofity.Remove is preceded by fsnotify.Chmod.
if op&fsnotify.Chmod != 0 {
time.Sleep(sleep_interval)
}
for {
if _, err := os.Stat(filename); err == nil {
if err := watcher.Add(filename); err == nil {
log.Printf("watching resumed for %s", filename)
return
}
}
time.Sleep(sleep_interval)
}
}
func WatchForUpdates(filename string, done <-chan bool, action func()) {
filename = filepath.Clean(filename)
watcher, err := fsnotify.NewWatcher()
if err != nil {
log.Fatal("failed to create watcher for ", filename, ": ", err)
}
go func() {
defer watcher.Close()
for {
select {
case _ = <-done:
log.Printf("Shutting down watcher for: %s", filename)
break
case event := <-watcher.Events:
// On Arch Linux, it appears Chmod events precede Remove events,
// which causes a race between action() and the coming Remove event.
// If the Remove wins, the action() (which calls
// UserMap.LoadAuthenticatedEmailsFile()) crashes when the file
// can't be opened.
if event.Op&(fsnotify.Remove|fsnotify.Rename|fsnotify.Chmod) != 0 {
log.Printf("watching interrupted on event: %s", event)
WaitForReplacement(filename, event.Op, watcher)
}
log.Printf("reloading after event: %s", event)
action()
case err := <-watcher.Errors:
log.Printf("error watching %s: %s", filename, err)
}
}
}()
if err = watcher.Add(filename); err != nil {
log.Fatal("failed to add ", filename, " to watcher: ", err)
}
log.Printf("watching %s for updates", filename)
}