Lambda¶

AWS Access Permissions¶

When using AWS APIs, it is best practice to utilize strict and well-defined IAM policies so users can only perform actions they have explicit access to.

Below are the permissions this data source type requires to properly function. Use this list to better define your IAM roles.

• lambda:ListFunctions
• lambda:InvokeFunction

Data source actions¶

Every Lambda function configured within the selected AWS region will be listed as a data source action. Once you select a Lambda function to invoke, you will need to configure the following properties:

• Payload Snippet: A Skuid JavaScript snippet used to construct the input payload that will be sent to, and processed by, the Lambda function.
• Response handler Snippet: (optional) A Skuid JavaScript snippet that processes the payload, if any, returned by the Lambda function.

Like other Skuid snippets, response handler snippets may be asynchronous by returning a Promise in the snippet. Skuid will wait for the Promise to be resolved before considering the Lambda function invocation to be complete.

Payload snippets¶

A payload must always be constructed for Lambda actions, even if the function requires no input. To construct a payload, use a payload snippet to return some value. That value’s data type will depend upon your function’s chosen software development kit (SDK)—for example, a Python function may expect a list be returned.

For instances where you do not need input, a simple snippet will do. As an example:

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return null

Otherwise, construct a more in-depth snippet to send along the proper input. A basic example passing in model data may look like:

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var model = skuid.model.getModel('myModel'),
  firstRow = model.getFirstRow();
return firstRow.myFieldname;

This input data would then be available to the Lambda function within the event object.

A basic example of a Lambda function using data within the event object—written in a Node.JS 8.10 runtime—would look like this:

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exports.handler = async (event) => {
  const response = {
    body: "I received this input: " + event
  };
  return response;
};

This function would simply respond with a message stating the value of what was passed in by the Skuid payload snippet.

Response handler snippets¶

If your Lambda function is returning data that will be used by models or components within the Skuid page, then use a response handler snippet to parse the function’s response.

Response handler snippets have access to the response sent by Lambda through arguments[0]. Reference AWS documentation for more information about the response elements.

A basic response handler snippet may look like this:

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var params = arguments[0],
  // And some variables for models if needed
  model = skuid.model.getModel('myModel'),
  firstRow = model.getFirstRow();

// To see each of the response elements
console.log(params);

// Or to log just the payload as written in the function
console.log(params.Payload);

// If the payload is a JSON object, parse it
var payload = JSON.parse(params.Payload);

// And, if applicable, update a model field with the payload's body
model.updateRow(firstRow, {ResponseFromLambda: payload.body});

Errors in Lambda functions¶

Note that Skuid will only return an “error” if there is a problem with Skuid receiving a response from Lambda, such as a network request error. Errors that come from logic within the function are considered successes by Skuid since they return a response.

Ensure the function’s error handling logic is within the function itself as opposed to the Skuid action list. Only use Skuid’s on-error actions for alerting the user that a network or processing error has occurred.

I do not see my functions available as data source actions. [[]]¶

• Ensure you’ve selected the correct region in the data source’s configuration.
• Ensure you have the appropriate AWS secret ID and key.
• Ensure you have the appropriate IAM permissions granted.