Lambda¶

AWS access permissions¶

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

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

• lambda:InvokeFunction
• lambda:ListFunctions

Creating an AWS authentication provider¶

Before configuring data sources within Skuid, you need to decide how you’ll authenticate to your AWS services using an IAM role. We recommend consulting your AWS administrator prior to making this decision.

Assume Role [[]]

This authentication method allows you to use the ARN of an assumable role instead of hard-coded AWS access keys. When a Skuid user makes a request using this authentication method, Skuid makes a secure server-side request to assume the configured role. If this request is successful, Skuid receives temporary access credentials, which Skuid caches until the credentials expire after 60 minutes.

Requests made through an assumed role are traceable via the AWS console. From there, you can see both the Skuid site and Skuid user who initiated the request, which provides AWS administrators full visibility into who requested access credentials and from what Skuid site.

Due to this method’s security and ease-of-management after initial setup, we typically recommend it over the access keys method. However, it does require some technical knowledge to configure. Be sure to read all of the instructions below.

Before you begin

Skuid can only access roles that have a defined path containing the string /skuid-assumable-role/ . This is different from the role’s name. Role paths can only be set when first created, so it isn’t possible to update an existing role with a new path.

In order to create a role with a path, you’ll need to use either the AWS IAM API or the AWS CLI.

The instructions below assume you are using AWS CLI (version 2) and that you’ve already configured an access key ID and secret access key for use with the CLI. Ensure these credentials have the iam:CreateRole permission. Command line examples are also tailored for Linux or macOS operating systems; commands for command line programs on Windows may differ.

Finally, because IAM roles require a trust relationship policy upon creation, you’ll need to save the JSON that Skuid provides when creating an authentication provider. Because of this you’ll need to navigate between your browser window, your computer’s file explorer, as well as the command line.

In Skuid

1. From the Skuid navigation bar, navigate to Data Sources > Authentication Providers.
2. Click Create.
3. Configure the authentication provider’s basic properties:
   • Name: Enter a name, such as AWSAuth.
   • Authentication Method: AWS: Assume Role with ARN
4. In the Trust Relationship Policy, click Copy to Clipboard.

This copied policy will enable your role to grant proper access to your Skuid site.

Note

If you want this role to be assumable by multiple Skuid sites—for example a staging site and a production site, make the sts:ExternalId property’s value into an array of Skuid site Ids.

For example, change this key/value:

"sts:ExternalId": "09583eba-de0e-49d3-ae42-61b3927a61b1"

Into this:

"sts:ExternalId": [
   "09583eba-de0e-49d3-ae42-61b3927a61b1",
   "e354e60f-5a80-4024-b01a-4cae13d0948c"
]

Site IDs are accessible from Settings > Site > Profile.

On your local machine

1. With the policy copied to your clipboard, paste the policy into a text editor.
2. Save the file to an easily accessible directory (for example, your desktop) on your machine with a recognizable name and the JSON file extension, like trust-policy.json

In a command line interface

With the trust policy saved to your machine, you can now use the AWS CLI to create an assumable role.

1. Open your command line program of choice and navigate to the directory containing your policy JSON file. For example, if you saved the file on your desktop:

   1	cd ~/Desktop

2. Use the AWS CLI’s iam create-role command to create the role with the proper path value and trust relationship policy:

   1	aws iam create-role --role-name Skuid-S3-Access --path /skuid-assumable-role/ --assume-role-policy-document file://trust-policy.json

   Note

   While role-name can vary from this example, the path must contain /skuid-assumable-role/

   The CLI creates the role, outputting its ARN and other related metadata. Because of the configured path, your ARN should look similar to this: arn:aws:iam::1234567891011:role/skuid-assumable-role/Skuid-S3-Access.

3. Copy this created ARN, either from the command line output or the AWS console.

In Skuid

1. Return to the authentication provider window.
2. Paste the copied ARN into the AWS Role ARN to assume field.
3. Click Save.

Access Keys [[]]

This authentication method utilizes an Amazon Web Service (AWS) IAM role’s access keys to authenticate to an AWS system.

If you are not the manager of your AWS services, follow along with Amazon’s steps for creating access keys with your IT administrator. You’ll need to do the following:

In AWS

1. Create a new group and select the appropriate policies for that group.
   • These should align with your intended Skuid use. Ensure your access policies match the services (S3, DynamoDB, or SNS) you’ll be using.
2. Create a new user in AWS Identity and Access Management (IAM) within the newly created group.
3. Retrieve the access credentials generated for that user:
   • The secret access key is only displayed once, immediately after the access key is generated, and cannot be found later. Be sure to copy it to a safe place.

In Skuid

With your access credentials handy, you can now use them to configure a Skuid authentication provider that will work with all AWS data sources.

1. Navigate to Configure > Data Sources > Authentication Providers.
2. Click New Authentication Provider.
3. Configure the authentication provider’s basic properties:
   • Name: Enter a name, such as AWSAuth.
   • Authentication Method: AWS: Access Keys
4. Enter your IAM role’s credential information:
   • AWS Access Key Id: The access key ID to use when authenticating.
   • AWS Secret Access Key: The secret access key to use when authenticating.
5. Click Save.

Creating a Lambda data source¶

1. Navigate to Data Sources > Data Sources.
2. Click Create.
3. Select Amazon Lambda for Type.
4. Enter an appropriate value for Name, such as AWS-ServiceName.
5. Click Next.
6. Select the previously configured AWS authentication provider.
7. Select the AWS Region where the resources you need within Skuid reside. See AWS documentation on regions for more information.
8. Click Save.

After creation, leave Use proxy disabled. The proxy does not currently support Amazon Lambda data sources.

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.