134 lines
3.1 KiB
Go
134 lines
3.1 KiB
Go
package aghos
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import (
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"fmt"
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"io"
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"io/fs"
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"path/filepath"
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"github.com/AdguardTeam/golibs/errors"
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"github.com/AdguardTeam/golibs/log"
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"github.com/fsnotify/fsnotify"
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)
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// event is a convenient alias for an empty struct to signal that watching
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// event happened.
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type event = struct{}
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// FSWatcher tracks all the fyle system events and notifies about those.
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//
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// TODO(e.burkov, a.garipov): Move into another package like aghfs.
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type FSWatcher interface {
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io.Closer
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// Events should return a read-only channel which notifies about events.
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Events() (e <-chan event)
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// Add should check if the file named name is accessible and starts tracking
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// it.
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Add(name string) (err error)
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}
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// osWatcher tracks the file system provided by the OS.
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type osWatcher struct {
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// w is the actual notifier that is handled by osWatcher.
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w *fsnotify.Watcher
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// events is the channel to notify.
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events chan event
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}
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const (
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// osWatcherPref is a prefix for logging and wrapping errors in osWathcer's
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// methods.
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osWatcherPref = "os watcher"
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)
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// NewOSWritesWatcher creates FSWatcher that tracks the real file system of the
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// OS and notifies only about writing events.
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func NewOSWritesWatcher() (w FSWatcher, err error) {
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defer func() { err = errors.Annotate(err, "%s: %w", osWatcherPref) }()
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var watcher *fsnotify.Watcher
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watcher, err = fsnotify.NewWatcher()
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if err != nil {
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return nil, fmt.Errorf("creating watcher: %w", err)
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}
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fsw := &osWatcher{
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w: watcher,
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events: make(chan event, 1),
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}
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go fsw.handleErrors()
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go fsw.handleEvents()
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return fsw, nil
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}
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// handleErrors handles accompanying errors. It used to be called in a separate
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// goroutine.
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func (w *osWatcher) handleErrors() {
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defer log.OnPanic(fmt.Sprintf("%s: handling errors", osWatcherPref))
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for err := range w.w.Errors {
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log.Error("%s: %s", osWatcherPref, err)
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}
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}
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// Events implements the FSWatcher interface for *osWatcher.
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func (w *osWatcher) Events() (e <-chan event) {
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return w.events
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}
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// Add implements the FSWatcher interface for *osWatcher.
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//
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// TODO(e.burkov): Make it accept non-existing files to detect it's creating.
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func (w *osWatcher) Add(name string) (err error) {
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defer func() { err = errors.Annotate(err, "%s: %w", osWatcherPref) }()
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if _, err = fs.Stat(RootDirFS(), name); err != nil {
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return fmt.Errorf("checking file %q: %w", name, err)
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}
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return w.w.Add(filepath.Join("/", name))
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}
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// Close implements the FSWatcher interface for *osWatcher.
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func (w *osWatcher) Close() (err error) {
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return w.w.Close()
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}
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// handleEvents notifies about the received file system's event if needed. It
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// used to be called in a separate goroutine.
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func (w *osWatcher) handleEvents() {
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defer log.OnPanic(fmt.Sprintf("%s: handling events", osWatcherPref))
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defer close(w.events)
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ch := w.w.Events
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for e := range ch {
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if e.Op&fsnotify.Write == 0 {
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continue
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}
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// Skip the following events assuming that sometimes the same event
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// occurrs several times.
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for ok := true; ok; {
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select {
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case _, ok = <-ch:
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// Go on.
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default:
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ok = false
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}
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}
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select {
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case w.events <- event{}:
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// Go on.
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default:
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log.Debug("%s: events buffer is full", osWatcherPref)
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}
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}
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}
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