The promises package brings asynchronous programming capabilities to R. Asynchronous programming is a technique used by many programming languages to increase scalability and responsiveness. Traditionally, this style of programming has not been useful to R users. But the advent of R web applications like Shiny has made async programming relevant.

This website provides a multi-step guide that will help familiarize you with several related concepts that are required for effective async programming. It is highly recommended that you go through the topics in order.


Installation

The promises package is not yet on CRAN, nor is an async-compatible version of Shiny. You can install both promises and an async-compatible version of Shiny with this command:

devtools::install_github("rstudio/shiny")

There are also some supporting packages that have experimental async-compatible branches:

devtools::install_github("ramnathv/htmlwidgets@async")
devtools::install_github("jcheng5/plotly@joe/feature/async")
devtools::install_github("rstudio/DT@async")

Contents

1. Why use promises?

Why do we need async programming? What is it good for, and not good for?

2. An informal intro to async programming

Async programming can require a serious mental shift, even for veteran programmers. This document attempts to introduce the “average” R user to the topic, as gently as possible.

3. Working with promises

A more thorough exploration of the concepts behind promises, and the API provided by the promises package.

4. Launching tasks

A guide to the future package, the place where we expect most async programming in R to begin.

5. Using promises with Shiny

Learn how to integrate promises into your Shiny applications.

6. Combining promises

Functions and techniques for working with multiple promises simultaneously.