AWS Lambda - Plugin

Looking for the plugin's configuration parameters? You can find them in the AWS Lambda configuration reference doc.

This plugin lets you invoke an AWS Lambda function from Kong Gateway. The AWS Lambda plugin can be used in combination with other request plugins to secure, manage, or extend the function.

Any form parameter sent along with the request is also sent as an argument to the AWS Lambda function.

Notes

By default, cURL sends payloads with an application/x-www-form-urlencoded MIME type, which will naturally be URL- decoded by Kong. To ensure special characters that are likely to appear in your AWS key or secret (like +) are correctly decoded, you must URL-encode them with --data-urlencode. Alternatives to this approach would be to send your payload with a different MIME type (like application/json), or to use a different HTTP client.

If you provide aws_key and aws_secret, they will be used in the highest priority to invoke the Lambda function.

If you do not provide an aws_key and aws_secret, the plugin uses an IAM role inherited from the instance running Kong.

The AWS Lambda plugin will automatically fetch the IAM role credential according to the following precedence order:

Fetch from the credentials defined in the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables.
Fetch from the profile and credential file, defined by AWS_PROFILE and AWS_SHARED_CREDENTIALS_FILE.
Fetch from the ECS container credential provider.
Fetch from the EKS IAM roles for the service account.
Fetch from the EC2 IMDS metadata. Both v1 and v2 are supported.

Note: IAM Identity Center credential provider and Process credential provider are not supported.

If you also provide the aws_assume_role_arn option, the plugin will try to perform an additional AssumeRole action. This requires the Kong process to make a HTTPS request to the AWS STS service API after configuring the AWS access key/secret or fetching credentials automatically from EC2/ECS/EKS IAM roles. If it succeeds, the plugin will fetch temporary security credentials that represents that the plugin now has the access permission configured in the target assumed role. Then the plugin will try to invoke the lambda function based on the target assumed role.

AWS region as environment variable

If the plugin configuration aws_region is unset, the plugin attempts to obtain the AWS region through environment variables AWS_REGION and AWS_DEFAULT_REGION, with the former taking higher precedence. For example, if both AWS_REGION and AWS_DEFAULT_REGION are set, the AWS_REGION value is used; otherwise, if only AWS_DEFAULT_REGION is set, its value is used. If neither configuration aws_region nor environment variables are set, a run-time error “no region or host specified” will be thrown.

Usage

Prerequisite: You must have access to the AWS Console as a user who is allowed to operate with lambda functions, and create users and roles.

First, create an execution role called LambdaExecutor for your lambda function.

In the IAM Console, create a new Role choosing the AWS Lambda service. There will be no policies because the function in this example will simply execute itself, returning a hardcoded JSON response without accessing other AWS resources.
Create a user named KongInvoker, used by the Kong API gateway to invoke the function.

In the IAM Console, create a new user. Programmatic access must be provided to the user via Access and Secret keys. Then, attach existing policies directly, particularly the predefined AWSLambdaRole. After the user creation is confirmed, store the Access Key and Secret Key in a safe place.
Next, create the lambda function itself in the N. Virginia Region (code us-east-1).

In Lambda Management, create a new function MyLambda. There will be no blueprint because you are going to paste the code below (which is an example code snippet). For the execution role, choose the LambdaExecutor created previously.

Note: The following code snippet is only an example. The Kong AWS Lambda plugin supports all runtimes provided by AWS. See the list of runtimes in the AWS Lambda > Functions > Create function dialog.
```
 import json
 def lambda_handler(event, context):
     """
       If is_proxy_integration is set to true :
       jsonbody='''{"statusCode": 200, "body": {"response": "yes"}}'''
     """
     jsonbody='''{"response": "yes"}'''
     return json.loads(jsonbody)
```
Test the lambda function from the AWS console and make sure the execution succeeds.
Set up a route in Kong and link it to the MyLambda function you just created.

With a database

Without a database

Create the route:

curl -i -X POST http://localhost:8001/routes \
--data 'name=lambda1' \
--data 'paths[1]=/lambda1'

Add the plugin:

curl -i -X POST http://localhost:8001/routes/lambda1/plugins \
--data 'name=aws-lambda' \
--data-urlencode 'config.aws_key={KongInvoker user key}' \
--data-urlencode 'config.aws_secret={KongInvoker user secret}' \
--data 'config.aws_region=us-east-1' \
--data 'config.function_name=MyLambda'

Add a route and plugin to the declarative config file:

routes:
- name: lambda1
  paths: [ "/lambda1" ]
plugins:
- route: lambda1
  name: aws-lambda
  config:
    aws_key: {KongInvoker user key}
    aws_secret: {KongInvoker user secret}
    aws_region: us-east-1
    function_name: MyLambda

Test your Lambda with Kong

After everything is created, make the http request and verify the correct invocation, execution, and response:

curl http://localhost:8000/lambda1

You should get a response back with the following headers from Amazon:

x-amzn-Remapped-Content-Length, X-Amzn-Trace-Id, x-amzn-RequestId

JSON response:

{"response": "yes"}

Have fun leveraging the power of AWS Lambda in Kong!

Next AWS Lambda Configuration