Looking into the @future

global class MyFutureClass {

  @future 
  static void myMethod(String a, Integer i) {
    System.debug('Method called with: ' + a + ' and ' + i);
    // Perform long-running code
  }
}
						

Allows you to kick-off long-running processes asynchronously to prevent CPU timeout

  @future (callout=true)
  public static void doCalloutFromFuture() {
   //Add code to perform callout
}						

• Adding the @future annotation allows a method to be called asynchronously
• Popular use case: making a callout from within a Trigger or after a DML statement

Limitations

• @future methods cannot call @future methods (including via triggers)
• Parameters can only be instances/collections of primitive types (no passing SObjects)
• Unknown execution order

• Future methods cannot call other future methods
• Parameters can only be primitives or collections thereof
• You have no guarantees one async method will fire before another even if it was initiated first

Workaround

Scheduler Ping Pong

* Slides taken from Dan Appleman's DF13 Session on Asynchronous Apex (Presentation) (Slides)

Queueable Apex

• Queueable apex provides job ids upon being enqueued, similar to batch apex
• Queueable apex classes can store complex data types within member variables
• Chaining jobs is possible without any sort of workarounds
• This makes the Scheduler Ping Pong method obsolete; especially because with the release of Queueable Apex Salesforce slowed down the scheduler method to enforce a 5 minute delay time between chains

Limitations

• Count against shared async method call limit
• 50 jobs added to the queue within a single transaction
• Only one job can be enqueued by queued apex

• Each queued apex call counts against a shared governor limit regarding async method calls within 24 hours
• You can enqueue only 50 queued apex jobs in one transaction
• Only one job can be added to the queue by queued apex
• Originally when this was first released in W15 you could only chain once, but now that limit has been removed

Schmimitations

• Each queued apex call counts against a shared governor limit regarding async method calls within 24 hours, but this is not a big deal as it's 250,000 or the number of user licenses in your organization multiplied by 200, whichever is greater
• You can enqueue 50 queued apex jobs in one transaction, but really you should only have to do this once and just create Async Request records elsewhere
• Only one job can be added to the queue by queued apex; again this is fine since we will just be chaining to run through our async request records

Chaining