Lightning Aura Components Developer Guide

Introducing Aura Components
Quick Start
Creating Components
Using Components
Communicating with Events
Communicating Across the DOM with Lightning Message Service
Creating Apps
Styling Apps
Developing Secure Code
Using JavaScript
Working with Salesforce Data
Lightning Data Service
Using Apex
Creating Server-Side Logic with Controllers
Testing Your Apex Code
Making API Calls from Apex
Make Long-Running Callouts with Continuations
Work with a Continuation in an Apex Class
@AuraEnabled Annotations for Continuations
Aura Component Continuations Example
Continuation-Specific Limits
Creating Components in Apex
Testing Components
Debugging
Performance
Reference
PDF

Note: This release is in preview. Features described here don’t become generally available until the latest general availability date that Salesforce announces for this release. Before then, and where features are noted as beta, pilot, or developer preview, we can’t guarantee general availability within any particular time frame or at all. Make your purchase decisions only on the basis of generally available products and features.

Make Long-Running Callouts with Continuations

Use the Continuation class in Apex to make a long-running request to an external web service. Process the response in a callback method. Continuations are the preferred way to manage callouts because they can provide substantial improvements to the user experience.

Using continuations has some advantages, including the capability to make callouts in parallel.

The framework queues up actions before sending them to the server. This mechanism is largely transparent to you when you’re writing code but it enables the framework to minimize network traffic by batching multiple actions into one request (XHR). The batching of actions is also known as boxcar’ing, similar to a train that couples boxcars together. Since continuations can be long-running requests, the framework essentially treats continuations as background actions. Continuations aren't boxcar'ed with other requests so they don't block other actions while they are running.

An asynchronous callout made with a continuation doesn’t count toward the Apex limit of synchronous requests that last longer than five seconds. Since Winter ’20, all callouts are excluded from the long-running request limit so continuations no longer offer an advantage for working with limits compared to regular callouts. However, we recommend using continuations to manage callouts due to the improved user experience.