Question

I have a ScheduledExecutorService and I do a task every 15 mins (in a web application in Tomcat).
In a ServletContextListener in contextDestroyed I have done:

Runtime.getRuntime().addShutdownHook(new Thread(){  
            @Override  
            public void run(){  
                scheduler.shutdown();   
            }   
        });    

The scheduler is started like:

final Runnable r = new Runnable(){

            @Override
            public void run() {
                System.out.println("My task");
                //Do some task
            }

        };
updater.scheduleWithFixedDelay(r, 30, 15, TimeUnit.MINUTES);

Question:On shutdown any remaining task isn’t executed.
There is a task running but I don’t see any logs so it seems it is not executed. Why?

UPDATE:
If I start tomcat and then after 2 mins I shutdown then isn’t the task considered as scheduled and must run? I mean if a task is submitted isn’t it considered as pending? Or it must be actually running?

Answer 1

I can’t quite parse your question but maybe your application is not exiting like you’d expect?

Shutting down an Executor will stop any tasks for being submitted but any running tasks will continue to run until they exit. From the shutdown() javadocs:

Initiates an orderly shutdown in which previously submitted
tasks are executed, but no new tasks will be accepted.
Invocation has no additional effect if already shut down.

If you edit your question to be more clear we can answer more appropriately.