We already covered basic threading in our core CFML section. In this section we will cover the usage of asynchronous programming via futures and the runAsync() function built-in to Adobe ColdFusion 2018+ and Lucee 5.3+.

A Future is an eventual result of an asynchronous operation.

runAsync()

This function returns a Future object, which is an eventual result of an asynchronous operation. Basically a representation of what the operation will produce, well, in the future. It takes in two arguments and returns a CFML Future object.

• callback:function - Closure/Lambda function that returns a result to be resolved

• timeout:numeric - Timeout for the asynchronous process in milliseconds

future = runAsync( function(){
	return "Hello World!";
} );
writeOutput( future.get() );
​
future = runAsync(function(){
       return 5;
} ).then( function( input ){
       return input + 2;
} );
result = future.get( 3 ); // 3 is timeout(in ms)
writeOutput(result);

The Future Object

The return of the runAsync() function is a CFML Future, not a Java Future. The Future Object has the following functions available:

With the future you can now create fluent functional programming constructs to deal with your async operation. You can create different error listeners and even continue processing the value the async operation produced in another asyncronous operation. Much like a pipeline of never ending futures!

future = runAsync( function(){
  return 5;
}).then( function(input){
  return input + 2;
}).error( function(){
  return "Error occurred.";
});
result = future.get();
writeOutput(result);

You can mix and match the callback functions to create a nice asyncronous pipeline. Just note that if you call the get() operation immediately that will BLOCK the execution until the async operation finalizes, which kinda defeats the purpose of the async operation. If you do not want to block, then use the then() approach, where that callback will be called for you with the result of the async operation and then you can do your post-processing. The alternative is to sit and poll the isDone() or isCancelled() operations, and YUCK!