82 lines
2.3 KiB
Go
82 lines
2.3 KiB
Go
package watcher
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import (
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"fmt"
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"os"
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"path/filepath"
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"time"
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"github.com/fsnotify/fsnotify"
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"github.com/oauth2-proxy/oauth2-proxy/v7/pkg/logger"
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)
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// WatchFileForUpdates performs an action every time a file on disk is updated
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func WatchFileForUpdates(filename string, done <-chan bool, action func()) error {
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filename = filepath.Clean(filename)
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watcher, err := fsnotify.NewWatcher()
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if err != nil {
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return fmt.Errorf("failed to create watcher for '%s': %s", filename, err)
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}
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go func() {
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defer watcher.Close()
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for {
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select {
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case <-done:
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logger.Printf("shutting down watcher for: %s", filename)
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return
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case event := <-watcher.Events:
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filterEvent(watcher, event, filename, action)
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case err = <-watcher.Errors:
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logger.Errorf("error watching '%s': %s", filename, err)
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}
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}
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}()
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if err := watcher.Add(filename); err != nil {
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return fmt.Errorf("failed to add '%s' to watcher: %v", filename, err)
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}
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logger.Printf("watching '%s' for updates", filename)
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return nil
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}
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// Filter file operations based on the events sent by the watcher.
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// Execute the action() function when the following conditions are met:
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// - the real path of the file was changed (Kubernetes ConfigMap/Secret)
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// - the file is modified or created
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func filterEvent(watcher *fsnotify.Watcher, event fsnotify.Event, filename string, action func()) {
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switch filepath.Clean(event.Name) == filename {
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// In Kubernetes the file path is a symlink, so we should take action
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// when the ConfigMap/Secret is replaced.
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case event.Op&fsnotify.Remove != 0:
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logger.Printf("watching interrupted on event: %s", event)
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WaitForReplacement(filename, event.Op, watcher)
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action()
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case event.Op&(fsnotify.Create|fsnotify.Write) != 0:
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logger.Printf("reloading after event: %s", event)
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action()
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}
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}
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// WaitForReplacement waits for a file to exist on disk and then starts a watch
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// for the file
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func WaitForReplacement(filename string, op fsnotify.Op, watcher *fsnotify.Watcher) {
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const sleepInterval = 50 * time.Millisecond
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// Avoid a race when fsnofity.Remove is preceded by fsnotify.Chmod.
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if op&fsnotify.Chmod != 0 {
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time.Sleep(sleepInterval)
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}
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for {
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if _, err := os.Stat(filename); err == nil {
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if err := watcher.Add(filename); err == nil {
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logger.Printf("watching resumed for '%s'", filename)
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return
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}
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}
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time.Sleep(sleepInterval)
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}
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}
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