Queueing of Server-Side Actions

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.

Multiple actions sent in the same boxcar are processed in one transaction.

The framework uses a stack to track the actions to send to the server. When the browser finishes processing events and JavaScript on the client, the enqueued actions on the stack are sent to the server in a batch.

If your action isn’t executing, make sure that you’re not executing code outside the framework’s normal rendering lifecycle. For example, if you use window.setTimeout() in an event handler to execute some logic after a time delay, wrap your code in $A.getCallback().

Tip

There are some properties that you can set on an action to influence how the framework manages the action while it’s in the queue waiting to be sent to the server. For more information, see:

Action Limit in a Boxcar Request

The framework returns a 413 HTTP response status code if there are more than 250 actions in a boxcar request. If a user sees this rare error, consider redesigning your custom component to follow best practices and reduce the number of actions in a request.