MultiTaskScheduler

Executes, in parallel, a list of tasks, and every task runs periodically at the specified frequency.

It sets the thread name for each task, instead of using the default one (e.g. pool-1-thread-3 or the fixed name from ThreadFactory). This might be useful for logging and monitoring the application.

It also offers a more straightforward way to set error handlers.

The MultiTaskScheduler is implementing AutoCloseable, which permits to use it with a try-catch with resources.

The coordinator is a platform thread(daemon=true) and is used strictly to start the tasks at the needed time.

The task executor is Executors #newThreadPerTaskExecutor with factory as Thread #ofVirtual which is used to execute the task.

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The behavior of MultiTaskScheduler is similar with ScheduledThreadPoolExecutor#scheduleAtFixedRate.

But if a task takes longer to execute than its scheduling frequency, subsequent executions will be skipped, instead of being queued.

Example of scheduleAtFixedRate behavior:

• Frequency: 100ms
• Normal execution time: under 100ms
• Edge case: execution may take 650ms, which is longer than the frequency.

Expected schedule: 0, 100, 200, 300, ..., 600, 700, ...

The behavior when a run last 650ms:

• Moment 0 : task starts and runs for 1 second.
• Moment 650: the first task ends. The scheduled runs from 100, 200, ... 600 are overdue. So the scheduler executes them immediately back-to-back without pause. Like a burst of execution.

In this case, the MultiTaskScheduler will drop the executions from 100, 200, ... 600, and will wait until 700, when starts a new task.

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How to use it:

New instance

MultiTaskScheduler scheduler = new MultiTaskScheduler((thread, ueh) -> { //handle the unhandled exception. });

Add task

scheduler.addTask( "NameOfTask", //should be unique 5_000, //start with delay in ms 1_000, //frequency of execution in ms () -> { /* the task code */ } (e) -> { /* handel the errors in task */ } );

Remove task

scheduler.removeTask("NameOfTask");

Start the scheduler

scheduler.start();

Stop the scheduler

manually: scheduler.close();

automatically: try(MultiTaskScheduler scheduler = new MultiTaskScheduler((thread, ueh) -> {}))