topic Re: Timer start event not starting all process instances in Alfresco Archive

Timer start event not starting all process instances

tushard — Thu, 11 Oct 2012 00:09:15 GMT

Hi,I would like to know what happens if a timer start event tries to start a process instance when the number of job executor threads specified by the corePoolSize are exhausted. I observed that in such a case, the timer start event failed to start a process instance. I now describe my experiment

Re: Timer start event not starting all process instances

frederikherema1 — Thu, 11 Oct 2012 13:01:05 GMT

If the thead-pool is exhausted, an implementation of the following class is consulted:


/**
 * <p>Strategy for handling jobs that were acquired but cannot be 
 * executed at this point (queue-size exceeded).</p> 
 * 
 * @author Daniel Meyer
 */
public interface RejectedJobsHandler {

  public void jobsRejected(JobExecutor jobExecutor, List<String> jobIds);  
  
}

By default (CallerRunsRejectedJobsHandler), the calling thread is used to run the job that should have been run by the pool. In most cases, this is the job-aquisition-thread. So any subsequent jobs that need to be executed (while the aquire-jobs thread is busy executing the job) WON'T be executed or added to the pool until the aquisition-thread is freed up again.

As this is sometimes not required behavior, you can implement your custom strategy and plug in in using the ProcessEngineConfiguration.

Re: Timer start event not starting all process instances

tushard — Sun, 14 Oct 2012 23:04:44 GMT

Hi,

You said that

By default (CallerRunsRejectedJobsHandler), the calling thread is used to run the job that should have been run by the pool. In most cases, this is the job-aquisition-thread.

Does this mean that when the thread pool is exhausted, the job-acquisition-thread is forced to execute a job and therefore, any further jobs are not added to the pool until the aquisition-thread is freed up again.

- Tushar

Re: Timer start event not starting all process instances

frederikherema1 — Mon, 15 Oct 2012 07:48:29 GMT

Yes, by default, it is. You can change this behavior any way you'd like…

Re: Timer start event not starting all process instances

tushard — Mon, 15 Oct 2012 17:23:33 GMT

RejectedJobsHandler and CallerRunsRejectedJobsHandler are part of Activiti 5.10, however, we are using Activiti 5.8 in our project. Inspection of the executeJobs method of the JobExecutor shows that RejectedExecutionException handling is not implemented in Activiti 5.8. Can I implement rejected jobs handler in Activiti 5.8 or is it better to upgrade to Activiti 5.10?

In Activiti 5.10, is it ok if I implement following custom rejected jobs handling policy? Here, I am asking the jobExecutor to retry the rejected jobs.

public class MyRejectedJobsHandler implements RejectedJobsHandler {
 public void jobsRejected(JobExecutor jobExecutor, List<String> jobIds) {
     jobExecutor.executeJobs(jobIds);
 }
}

- Tushar

Re: Timer start event not starting all process instances

jbarrez — Tue, 16 Oct 2012 09:44:27 GMT

It's always good to upgrade to the latest version of Activiti. We're working very hard to make it better with every release 😉

I guess the policy might work, but if the jobs were rejected because of an overload, you're just making the problem worse …
A more elegant solution would be to put them on a waiting queue and retry a bit later on.

Or, just use the CallerRunsRejectedJobsHandler. That one will definitly execute the job, using the current thread (which might slow down the job execution … which is a good thing if the system is saturated).