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Scheduled Tasks

Requirements

The async package is what powers scheduled tasks and it can be available to any CFML application by using any of our standalone libraries and frameworks:

YOU DON'T NEED COLDBOX TO RUN ANY SCHEDULED TASKS OR ANY FEATURES OF THE ASYNC PACKAGE. YOU CAN USE ANY OF THE STANDALONE LIBRARIES ABOVE.

However, if you use ColdBox, you get enhanced features and new functionality. For example, the ColdBox Scheduled Tasks are an enhanced implementation of the core scheduled tasks we will be reviewing in this document.

Introduction

The async package offers you the ability to schedule tasks and workloads via the Scheduled Executors that you can register in the async manager. We also provide you with a lovely Scheduler class that can keep track of all the tasks you would like to be executing in a ScheduledExecutor. In essence, you have two options when scheduling tasks:

  1. Scheduler Approach: Create a scheduler and register tasks in it

  2. Scheduled Executor Approach: Create a ScheduledExecutor and send task objects into it

With our scheduled tasks you can run either one-off tasks or periodically tasks.

Scheduler Approach

To create a new scheduler you can call the Async Managers' newScheduler( name ) method. This will create a new coldbox.system.async.tasks.Scheduler object with the specified name you pass. It will also create a ScheduledExecutor for you with the default threads count inside the scheduler.. It will be then your responsibility to persist that scheduler so you can use it throughout your application process.

application.scheduler = asyncmanager.newScheduler( "appScheduler" );

Once you get an instance to that scheduler you can begin to register tasks on it. Once all tasks have been registered you can use the startup() method to startup the tasks and the shutdown() method to shutdown all tasks and the linked executor.

The name of the ScheduledExecutor will be {schedulerName}-scheduler

Application.cfc
component{
    
    this.name = "My App";
    
    
    function onApplicationStart(){
        new wirebox.system.Injector();
        application.asyncManager = application.wirebox.getInstance( "wirebox.system.async.AsyncManager" );
        application.scheduler = application.asyncmanager.newScheduler( "appScheduler" );

          /**
           * --------------------------------------------------------------------------
           * Register Scheduled Tasks
           * --------------------------------------------------------------------------
           * You register tasks with the task() method and get back a ColdBoxScheduledTask object
           * that you can use to register your tasks configurations.
           */
          	
          application.scheduler.task( "Clear Unregistered Users" )
          	.call( () => application.wirebox.getInstance( "UsersService" ).clearRecentUsers() )
          	.everyDayAt( "09:00" );
          	
          application.scheduler.task( "Hearbeat" )
          	.call( () => runHeartBeat() )
          	.every( 5, "minutes" )
          	.onFailure( ( task, exception ) => {
          			sendBadHeartbeat( exception );
          	} );
          
          // Startup the scheduler
          application.scheduler.startup();
    
    }


    function onApplicationEnd( appScope ){
        // When the app is restart or dies make sure you cleanup
        appScope.scheduler.shutdown();
        appScope.wirebox.shutdown();
    }


}

Configuration Methods

The following methods are used to impact the operation of all scheduled tasks managed by the scheduler:

Timezone For All Tasks

By default, all tasks run under the system default timezone which usually is UTC. However, if you would like to change to a different execution timezone, then you can use the setTimeZone() method and pass in a valid timezone string: 

setTimezone( "America/Chicago" )

You can find all valid time zone Id's here: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/time/ZoneId.html

Remember that some timezones utilize daylight savings time. When daylight saving time changes occur, your scheduled task may run twice or even not run at all. For this reason, we recommend avoiding timezone scheduling when possible.

Custom Executor

By default the scheduler will register a scheduled executor with a default of 20 threads for you with a name of {schedulerName}-scheduler. If you want to add in your own executor as per your configurations, then just call the setExecutor() method.

setExecutor( 
    getAsyncManager().newScheduledExecutor( "mymymy", 50 ) 
);

You can find how to work with executors in our executors section.

Scheduler Properties

Every scheduler has the following properties available to you in the variables scope

Scheduler Utility Methods

Every scheduler has several utility methods:

Scheduling Tasks

Ok, now that we have seen all the capabilities of the scheduler, let's dive deep into scheduling tasks with the task( name ) method.

Registering Tasks

Once you call on this method, the scheduler will create a ColdBoxScheduledTask object for you, configure it, wire it, register it and return it to you. 

task( "my-task" )

You can find the API Docs for this object here: https://s3.amazonaws.com/apidocs.ortussolutions.com/coldbox/6.4.0/coldbox/system/async/tasks/ScheduledTask.html

Task Closure/Lambda/Object

You register the callable event via the call() method on the task object. You can register a closure/lambda or a invokable CFC. If you register an object, then we will call on the object's run() method by default, but you can change it using the method argument and call any public/remote method.

// Lambda Syntax
task( "my-task" )
    .call( () => runcleanup() )
    .everyHour();
    
// Closure Syntax
task( "my-task" )
    .call( function(){
        // task here
    } )
    .everyHourAt( 45 );
    
// Object with run() method
task( "my-task" )
    .call( wirebox.getInstance( "MyObject" ) )
    .everyDay()
    
// Object with a custom method
task( "my-task" )
    .call( wirebox.getInstance( "MyObject" ), "reapCache" )
    .everydayAt( "13:00" )

Frequencies

There are many many frequency methods in scheduled tasks that will enable the tasks in specific intervals. Every time you see that an argument receives a timeUnit the available options are:

  • days

  • hours

  • minutes

  • seconds

  • milliseconds (default)

  • microseconds

  • nanoseconds

Ok, let's go over the frequency methods:

All time arguments are defaulted to midnight (00:00)

Preventing Overlaps

By default all tasks that have interval rates/periods that will execute on that interval schedule. However, what happens if a task takes longer to execute than the period? Well, by default the task will execute even if the previous one has not executed. If you want to prevent this behavior, then you can use the withNoOverlaps() method and ColdBox will register the tasks with a fixed delay. Meaning the intervals do not start counting until the last task has finished executing.

task( "test" )
	.call( () => getInstance( "CacheService" ).reap() )
	.everyMinute()
	.withNoOverlaps();

Spaced delays are a feature of the Scheduled Executors. There is even a spacedDelay( delay, timeUnit ) method in the Task object.

Delaying First Execution

Every task can also have an initial delay of first execution by using the delay() method.

/**
 * Set a delay in the running of the task that will be registered with this schedule
 *
 * @delay The delay that will be used before executing the task
 * @timeUnit The time unit to use, available units are: days, hours, microseconds, milliseconds, minutes, nanoseconds, and seconds. The default is milliseconds
 */
ScheduledTask function delay( numeric delay, timeUnit = "milliseconds" )

The delay is numeric and the timeUnit can be:

  • days

  • hours

  • minutes

  • seconds

  • milliseconds (default)

  • microseconds

  • nanoseconds

// Lambda Syntax
task( "my-task" )
    .call( () => wirebox.getInstance( "MyObject" ).runcleanup() )
    .delay( "5000" )
    .everyHour();

Please note that the delay pushes the execution of the task into the future only for the first execution.

One Off Tasks

A part from registering tasks that have specific intervals/frequencies you can also register tasks that can be executed ONCE ONLY. These are great for warming up caches, registering yourself with control planes, setting up initial data collections and so much more.

Basically, you don't register a frequency just the callable event. Usually, you can also combine them with a delay of execution, if you need them to fire off after certain amount of time has passed.

task( "build-up-cache" )
    .call( () => wirebox.getInstance( "MyObject" ).buildCache() )
    .delay( 1, "minutes" );
    
task( "notify-admin-server-is-up" )
    .call( () => wirebox.getInstance( "MyObject" ).notifyAppIsUp( getUtil().getServerIp() ) )
    .delay( 30, "seconds" );
    
task( "register-container" )
    .call( () => ... )
    .delay( 30, "seconds" );

Life-Cycle Methods

We already saw that a scheduler has life-cycle methods, but a task can also have several useful life-cycle methods:

task( "testharness-Heartbeat" )
	.call( function() {
			if ( randRange(1, 5) eq 1 ){
				 throw( message = "I am throwing up randomly!", type="RandomThrowup" );
			}
			  writeDump( var='====> I am in a test harness test schedule!', output="console" );
		} )
		.every( "5", "seconds" )
		.before( function( task ) {
			  writeDump( var='====> Running before the task!', output="console" );
		} )
		.after( function( task, results ){
			  writeDump( var='====> Running after the task!', output="console" );
		} )
		.onFailure( function( task, exception ){
			  writeDump( var='====> test schedule just failed!! #exception.message#', output="console" );
		} )
		.onSuccess( function( task, results ){
			  writeDump( var="====> Test scheduler success : Stats: #task.getStats().toString()#", output="console" );
		} );

Timezone

By default, all tasks will ask the scheduler for the timezone to run in. However, you can override it on a task-by-task basis using the setTimezone( timezone ) method:

setTimezone( "America/Chicago" )

You can find all valid time zone Id's here: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/time/ZoneId.html

Remember that some timezones utilize daylight savings time. When daylight saving time changes occur, your scheduled task may run twice or even not run at all. For this reason, we recommend avoiding timezone scheduling when possible.

Truth Test Constraints

There are many ways to constrain the execution of a task. However, you can register a when() closure that will be executed at runtime and boolean evaluated. If true, then the task can run, else it is disabled.

task( "my-task" )
    .call( () => wirebox.getInstance( "MyObject" ).cleanOldUsers() )
    .daily()
    .when( function(){
        // Can we run this task?
        return true;
    );

Disabling/Pausing Tasks

Every task is runnable from registration according to the frequency you set. However, you can manually disable a task using the disable() method:

task( "my-task" )
    .call( () => getInstance( "securityService" ).cleanOldUsers() )
    .daily()
    .disable();

Once you are ready to enable the task, you can use the enable() method:

myTask.enable()

Task Stats

All tasks keep track of themselves and have lovely metrics. You can use the getStats() method to get a a snapshot structure of the stats in time. Here is what you get in the stats structure:

/**
 * Called after ANY task runs
 *
 * @task The task that got executed
 * @result The result (if any) that the task produced
 */
function afterAnyTask( required task, result ){
	log.info( "task #task.getName()# just ran. Metrics: #task.getStats().toString()# ");
}

Task Helpers

We have created some useful methods that you can use when working with asynchronous tasks:

Scheduled Executor Approach

Let's investigate now a second approach to task scheduling. We have seen the Scheduler approach which is a self-contained object that can track multiple tasks for you and give you enhanced and fluent approaches to scheduling. However, there are times, where you just want to use a ScheduledExecutor to send tasks into for either one-time executions, or also on specific frequencies and skip the Scheduler.

Like with anything in life, there are pros and cons. The Scheduler approach will track all the scheduled future results of each task so you can see their progress, metrics and even cancel them. With this approach, it is more of a set off and forget approach.

Register a Scheduled Executor

Let's get down to business. The first step is to talk to the AsyncManager and register a scheduled executor. You can do this using two methods:

  • newExecutor( name, type, threads ) - Pass by type

  • newScheduledExecutor( name, threads ) - Shorthand

// Create it with a default of 20 threads
application.asyncManager.newExecutor( "myTasks", "scheduled" );
// Create it with a default of 10 threads
application.asyncManager.newExecutor( "myTasks", "scheduled", 10 );
// Create it as a FIFO queue of 1 thread
application.asyncManager.newExecutor( "myTasks", "scheduled", 1 );


// Create it with a default of 20 threads
application.asyncManager.newScheduledExecutor( "myTasks" );
// Create it with a default of 10 threads
application.asyncManager.newScheduledExecutor( "myTasks", 10 );
// Create it as a FIFO queue of 1 threa,d
application.asyncManager.newScheduledExecutor( "myTasks", 1 );

Once you register the executor the Async Manager will track it's persistence and then you can request it's usage anywhere in your app via the getExecutor( name ) method or inject it using the executors injection DSL.

// Request it
var executor = application.asyncManager.getExecutor( "myTasks" );

// Inject it
property name="myTasks" inject="executor:myTasks";

Scheduling

Now that we have a scheduler, we can use the newTask() method to get a ScheduledTask , configure it, and send it for execution.

// Request it
var executor = application.asyncManager.getExecutor( "myTasks" );

var future = executor.newTask( "cache-reap" )
    .call( () => application.cacheFactory.reapAll() )
    .every( 5, "minutes" )
    .start();

As you can see, now we are in Scheduling Tasks mode, and all the docs on it apply. Several things are different in this approach:

  1. We talk to the executor via the newTask() method to get a new ScheduledTask object

  2. We call the start() method manually, whenever we want to send the task into scheduling

  3. We get a ScheduledFuture result object so we can track the results of the schedule.

Work Queues

You can very easily create working queues in this approach by being able to send one-off tasks into the executors and forget about them. Let's say we have an app that needs to do some image processing afte ran image has been uploaded. We don't want to hold up (block) the calling thread with it, we upload, send the task for processing and return back their identifier for the operation. 

... Upload File.

// Process Image in the Executor Work Queue
executor.newSchedule( task : function(){
        application.wirebox.getInstance( "ImageProcessor" ).processImage( fileName );
    }).start();
    
... Continue operation

Remember you can set how many threads you want in a executor. It doesn't even have to be a scheduled executor, but could be a cached one which can expand and contract according to work loads.

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