Hi all, allow this code to explain:
public class ParseTask implements Runnable {
private static final Logger _log = Logger.getLogger();
private static final ThreadFactory factory = new
ONExceptionThreadFactory(new ONExceptionHandler());
private static final ExecutorService executorService =
Executors.newSingleThreadScheduledExecutor(factory);
private static final BinaryLatch binaryLatch = new BinaryLatch();
public void run() {
if (binaryLatch.isRunning()) {
// skip task if its already running
return;
}
Future future = executorService.submit(new ParseJob());
try {
// wait and timeout or return result
future.get(300, TimeUnit.SECONDS);
} catch (InterruptedException ex) {
_log.error(ex.getMessage(), ex);
// Re-assert the thread's interrupted status
Thread.currentThread().interrupt();
// We don't need the result, so cancel the task too
future.cancel(true);
} catch (Exception ex) {
_log.error(ex.getMessage(), ex);
throw ThreadUtils.launderThrowable(ex.getCause());
}
}
}
This ParseTask is started via a Servlet init() as:
ScheduledExecutorService ses = Executors.newSingleThreadScheduledExecutor();
ScheduledFuture <?> scheduledParseJob = ses.scheduleWithFixedDelay(new
ParseTask(),
0L, 1, TimeUnit.MINUTES);
Problem: I want to write a latch, perhaps a semaphore, that skips this
task if its already running. So I want to acquire some type of lock
when I start this task, skip the task if its already been started, and
release the lock when this single task is completed. CountDownLatch
doesn't seem right for a repeatable task. I've written a few versions
of BinaryLatch but nothing seems right to me. Any ideas?
Robert
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