Class PushFileWatcher

One java.nio.file.WatchService over the files the Push Notification (PN) engine re-reads when they change: the credentials file and, later, the files it names. No polling (ruling S-5, 2026-09-26): the thread blocks in WatchService.take() and the operating system wakes it.

A WatchService watches directories, so a file is watched through its parent: every event naming the file counts, ENTRY_CREATE included, because editors save by writing a new file and renaming it into place, which arrives as a delete and a create rather than a modify. A burst of events - a save is typically two or three - is debounced into one callback: after the first event the thread waits DEBOUNCE_MILLIS of quiet (WatchService.poll(long,TimeUnit) on the event queue, not on the file) before it runs the callbacks, and every further event restarts the wait. An OVERFLOW runs every callback of that directory, since it is not known which file changed.

One thread, a daemon, named at construction; it ends when close() closes the service. The callbacks run on it, one after the other, and a callback that throws is logged SEVERE and does not stop the watcher.

The tree's other WatchService user, com.iizix.server.app.HotDeploy, is a one-shot change detector bound to an application definition - its first change sets a flag and closes the service - so it cannot serve a file that is reloaded again and again, which is why this class exists beside it.