Using Tailer and WatchService

Question

I use Tailer and WatchService at the same time by using this code:

AgentTailerListener listener = new AgentTailerListener();
Tailer tailer;

WatchService watcher = FileSystems.getDefault().newWatchService();
while (true) {
    WatchKey watchKey;
    watchKey = Paths.get("/tmp").register(watcher, ENTRY_CREATE);
    watchKey = watcher.take();

    for (WatchEvent<?> event : watchKey.pollEvents()) {
        if (event.kind() == StandardWatchEventKinds.ENTRY_CREATE) {
            tailSource = event.context().toString();
            System.out.println(tailSource);
            File file = new File("/tmp/" + tailSource);
            String end = "log";

            if (file.getName().endsWith(end)) {
                tailer = TailerFactory.createTailer(file, listener);
                (new Thread(tailer)).start();
            }

        }
    }

    watchKey.reset();
    transport.close();
}

But the problem is: I want to check only one file with the tailer (like stoping the thread, but I can’t stop a thread specific to a file), and when I write in a file by the echo command, not all the letters I wrote appear.

When I write the same text with echo several times in a row all the letters are written.

I saw this topic, How to tail -f the latest log file with a given pattern, but I don’t know if I can use it for my problem (I don’t know the difference between tail and tailer).

Chènevis · Answer 1 · 2015-07-24T16:23:00.723

Finally, I think this works better:

AgentTailerListener listener = new AgentTailerListener();
Tailer tailer;
String tailSource;
Thread thread;

WatchService watcher = FileSystems.getDefault().newWatchService();

WatchKey watchKey;
watchKey = Paths.get("/tmp").register(watcher, ENTRY_CREATE);

List<Thread> threadList = new ArrayList<Thread>();
while (true) {
    watchKey = watcher.take();
    for (WatchEvent<?> event : watchKey.pollEvents()) {
    if (event.kind() == StandardWatchEventKinds.ENTRY_CREATE) {

        tailSource = event.context().toString();
        System.out.println(tailSource);
        File file = new File("/tmp/" + tailSource);
        String end = "log";
        if (file.getName().endsWith(end)) {
            tailer= TailerFactory.createTailer(file, listener);
            if(threadList.isEmpty()){}
            else{
                Thread.sleep(1000);
                threadList.get(0).stop();
                threadList.clear();}
            System.out.println(threadList.size());
            threadList.add(thread = new Thread(tailer));
            threadList.get(0).start();
            }
    }
}
watchKey.reset();

}

But it creates very many threads, I think I have to use a fix thread pool.

Using Tailer and WatchService

1 Answers1