scheduler thread pool?

[sam ”]

Hey,

I am using org.apache.sling.commons.scheduler.Scheduler   to run a job with
run() method, every 60 seconds.

Looking at log, it looks like there are 5 threads accessing run() method..
05.08.2011 11:18:46.084 *DEBUG* [pool-1-thread-1]
com.example.RemoteFeedService Finishing run() in RemoteFeedService
05.08.2011 11:18:46.084 *DEBUG* [pool-1-thread-5]
com.example.RemoteFeedService Starting run() in RemoteFeedService
05.08.2011 11:18:46.084 *DEBUG* [pool-1-thread-2]
com.example.RemoteFeedService Starting run() in RemoteFeedService
05.08.2011 11:18:46.085 *DEBUG* [pool-1-thread-3]
com.example.RemoteFeedService Starting run() in RemoteFeedService
05.08.2011 11:18:46.085 *DEBUG* [pool-1-thread-4]
com.example.RemoteFeedService Starting run() in RemoteFeedService
05.08.2011 11:18:46.085 *DEBUG* [pool-1-thread-3]
com.example.RemoteFeedService Starting run() in RemoteFeedService
05.08.2011 11:18:46.086 *DEBUG* [pool-1-thread-2]
com.example.RemoteFeedService Starting run() in RemoteFeedService
05.08.2011 11:19:03.928 *DEBUG* [pool-1-thread-5]
com.example.RemoteFeedService Starting run() in RemoteFeedService


I am registering the job to Scheduler as the following:
    @Activate
    private void activate(Map<String, ?> config) throws Exception {

        isEnabled = OsgiUtil.toBoolean(config.get(IS_ENABLED), false);
        schedPeriod = OsgiUtil.toLong(config.get(SCHEDULE_PERIOD), 0);

        removeJob();
        if (isEnabled && schedPeriod > 0) {
            scheduler.addPeriodicJob(JOB_NAME, this, null, schedPeriod,
true);
        }
    }
    private void removeJob() {
        try {
            scheduler.removeJob(JOB_NAME);
        } catch (final NoSuchElementException e) {
            LOG.info("No job to remove: " + JOB_NAME);
        }
    }



I want only one thread to run   run() method every minute.
And, if previous run() haven't finished yet the next minute, it should not
run...

I tried  synchronized:
public synchronized void run() {
...


But then it seems like there's deadlock...


1.  why are there 5 threads accessing run() ?
2. how can i limit the number of threads for Scheduler  (for this job only)?
3. how can I make run() method into critical section? (only one thread
executes it.  while a thread is executing it, no other thread can execute
it..)