mirror of
https://github.com/edgelesssys/constellation.git
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119 lines
2.7 KiB
Go
119 lines
2.7 KiB
Go
/*
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Copyright (c) Edgeless Systems GmbH
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SPDX-License-Identifier: AGPL-3.0-only
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*/
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// Package watcher implements a file watcher to update an object on file changes.
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package watcher
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import (
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"fmt"
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"log/slog"
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"github.com/fsnotify/fsnotify"
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)
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// FileWatcher watches for changes to the file and calls the waiter's Update method.
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type FileWatcher struct {
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log *slog.Logger
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updater updater
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watcher eventWatcher
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done chan struct{}
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}
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// New creates a new FileWatcher for the given validator.
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func New(log *slog.Logger, updater updater) (*FileWatcher, error) {
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watcher, err := fsnotify.NewWatcher()
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if err != nil {
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return nil, err
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}
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return &FileWatcher{
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log: log,
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watcher: &fsnotifyWatcher{watcher},
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updater: updater,
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done: make(chan struct{}, 1),
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}, nil
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}
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// Close closes the watcher.
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// It should only be called once.
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func (f *FileWatcher) Close() error {
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err := f.watcher.Close()
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<-f.done
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return err
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}
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// Watch starts watching the file at the given path.
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// It will call the watcher's Update method when the file is modified.
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func (f *FileWatcher) Watch(file string) error {
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log := f.log.With("file", file)
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defer func() { f.done <- struct{}{} }()
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if err := f.watcher.Add(file); err != nil {
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return err
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}
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for {
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select {
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case event, ok := <-f.watcher.Events():
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if !ok {
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log.Info("Watcher closed")
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return nil
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}
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// file changes may be indicated by either a WRITE, CHMOD, CREATE or RENAME event
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if event.Op&(fsnotify.Write|fsnotify.Chmod|fsnotify.Create|fsnotify.Rename) != 0 {
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if err := f.updater.Update(); err != nil {
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log.With(slog.Any("error", err)).Error("Update failed")
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}
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}
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// if a file gets removed, e.g. by a rename event, we need to re-add the file to the watcher
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if event.Has(fsnotify.Remove) {
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if err := f.watcher.Add(event.Name); err != nil {
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log.With(slog.Any("error", err)).Error("Failed to re-add file to watcher")
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return fmt.Errorf("failed to re-add file %q to watcher: %w", event.Name, err)
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}
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}
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case err := <-f.watcher.Errors():
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if err != nil {
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log.With(slog.Any("error", err)).Error("Watching for measurements updates")
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return fmt.Errorf("watching for measurements updates: %w", err)
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}
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}
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}
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}
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type updater interface {
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Update() error
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}
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type eventWatcher interface {
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Add(string) error
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Close() error
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Events() <-chan fsnotify.Event
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Errors() <-chan error
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}
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type fsnotifyWatcher struct {
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watcher *fsnotify.Watcher
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}
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func (w *fsnotifyWatcher) Add(file string) error {
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return w.watcher.Add(file)
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}
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func (w *fsnotifyWatcher) Close() error {
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return w.watcher.Close()
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}
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func (w *fsnotifyWatcher) Events() <-chan fsnotify.Event {
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return w.watcher.Events
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}
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func (w *fsnotifyWatcher) Errors() <-chan error {
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return w.watcher.Errors
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}
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