11 Asynchronous Programming
With modern hardware featuring multiple cores, many programming languages have been adding asynchronous, parallel programming APIs, Groovy being no exception.
Popular asynchronous libraries include:
RxJava - http://reactivex.io
GPars - http://gpars.org
Reactor - https://projectreactor.io
By building ontop of these various libraries the The Async features of Grails aim to simplify concurrent programming within the framework and include the concept of Promises and a unified event model.
In general since the Reactive programming model is an evolving space Grails tries to provide generic support for integrating a range of asynchronous libraries and doesn’t recommend any single library as they all have various advantages and disadvantages.
For more information on Asynchronous programming with Grails see the user guide for the Grails Asynchronous Framework.