Friday, March 31, 2023

Passing data from AWS EventBridge Scheduler to Lambda

The documentation was lacking images, or even descriptions of some screens ("Choose Next. Choose Next.")  So, I ran a little experiment to test things out.

When creating a new scheduled event in AWS EventBridge Scheduler, then choosing AWS Lambda: Invoke, a field called "Input" will be available.  It's pre-filled with the value of {}, that is, an empty JSON object. This is the value that is passed to the event argument of the Lambda handler:

export async function handler(event, context) {
  // handle the event

With an event JSON of {"example":{"one":1,"two":2}}, the handler could read event.example.two to get its value, 2.

It appears that EventBridge Scheduler allows one complete control over this data, and the context argument is only filled with Lambda-related information.  Therefore, AWS provides the ability to include the <aws.scheduler.*> values in this JSON data, to be passed to Lambda (or ignored) as one sees fit, rather than imposing any constraints of its own on the data format.  (Sorry, no examples; I was only testing the basic features.)

Note that the handler example above is written with ES Modules.  This requires the Node 18.x runtime in Lambda, along with a filename of "index.mjs".

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