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From "Xikui Wang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ASTERIXDB-1690) FileSystemWatcher.close() is blocked by FileSystemWatcher.take() when monitoring directory.
Date Wed, 12 Oct 2016 05:19:20 GMT
Xikui Wang created ASTERIXDB-1690:
-------------------------------------

             Summary: FileSystemWatcher.close() is blocked by FileSystemWatcher.take() when
monitoring directory.
                 Key: ASTERIXDB-1690
                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-1690
             Project: Apache AsterixDB
          Issue Type: Bug
          Components: Feeds
            Reporter: Xikui Wang


When create feed for directory monitoring, disconnect feed can be blocked by the FileSystemWatcher.
When FileSystemWatcher is waiting for new files, the whole object is locked by current thread.
So when another thread trying to close the watcher, it will be blocked. Here is the take()
method from FileSystemWatcher: 

{quote}
 public synchronized File take() throws IOException {
        File next = poll();
        if (next != null) {
            return next;
        }
        if (done || !isFeed) {
            return null;
        }
        // No file was found, wait for the filesystem to push events
        WatchKey key = null;
        lock.lock();
        try {
            while (!it.hasNext()) {
                try {
                    key = watcher.take();
                } catch (InterruptedException x) {
                    if (LOGGER.isEnabledFor(Level.WARN)) {
                        LOGGER.warn("Feed Closed");
                    }
                    if (watcher == null) {
                        return null;
                    }
                    continue;
                } catch (ClosedWatchServiceException e) {
                    if (LOGGER.isEnabledFor(Level.WARN)) {
                        LOGGER.warn("The watcher has exited");
                    }
                    if (watcher == null) {
                        return null;
                    }
                    continue;
                }
                handleEvents(key);
                if (endOfEvents(key)) {
                    return null;
                }
            }
        } finally {
            lock.unlock();
        }
        // files were found, re-create the iterator and move it one step
        return it.next();
    }
{quote}



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