When a Lambda function is exposed by an AWS API Gateway, the response of the function must be returned in a specific format. The gateway proxy in Gloo Gateway can understand this format and process the response in the same way as an AWS API gateway. Additionally, you can wrap requests to the Lambda function in the same format that an AWS API gateway uses. Applying a transformation to format requests to and responses from your function can help provide a smooth migration from AWS gateways to Gloo Gateway.

Wrap requests or unwrap responses

  1. Use the AWS Lambda console to create a Node.js function named unwrap-test. Use the following code for the function.

      export const handler = async(event) => {
    const response = {
        "statusCode": 201,
        "headers": {
            "key": "value"
        },
        "isBase64Encoded": false,
        "multiValueHeaders": { 
            "X-Custom-Header": ["My value", "My other value"],
        },
        "body": JSON.stringify({TotalCodeSize: 104330022,FunctionCount: 26})
    }
    return response;
};

  2. Apply the requestFormat: APIGateway or responseFormat: APIGateway transformations in a GlooTrafficPolicy resource. Note that you can apply one or both transformations in one resource.

      kubectl apply -f - <<EOF
apiVersion: gloo.solo.io/v1alpha1
kind: GlooTrafficPolicy
metadata:
  name: lambda-unwrap-transform
  namespace: gloo-system
spec:
  glooTransformation:
    awsLambda:
      requestFormat: APIGateway
      responseFormat: APIGateway
EOF

  3. Create a Backend resource to reference the unwrap-test function. The required fields vary based on your authentication method.

      kubectl apply -f - <<EOF
apiVersion: gateway.kgateway.dev/v1alpha1
kind: Backend
metadata:
  name: lambda-unwrap
  namespace: gloo-system
spec:
  type: AWS
  aws:
    region: ${AWS_LAMBDA_REGION}
    accountId: "${AWS_ACCOUNT_ID}"
    auth:
      type: Secret
      secretRef:
        name: aws-creds
    lambda:
      functionName: unwrap-test
      payloadTransformMode: None
EOF
  
      kubectl apply -f - <<EOF
apiVersion: gateway.kgateway.dev/v1alpha1
kind: Backend
metadata:
  name: lambda-unwrap
  namespace: gloo-system
spec:
  type: AWS
  aws:
    region: ${AWS_LAMBDA_REGION}
    accountId: "${AWS_ACCOUNT_ID}"
    lambda:
      functionName: unwrap-test
      payloadTransformMode: None
EOF

  4. Create an HTTPRoute resource that references the lambda-unwrap Backend and the lambda-unwrap-transform GlooTrafficPolicy.

      kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: lambda-unwrap
  namespace: gloo-system
spec:
  parentRefs:
    - name: http
      namespace: gloo-system
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /unwrap-test
    backendRefs:
    - name: lambda-unwrap
      namespace: gloo-system
      group: gateway.kgateway.dev
      kind: Backend
    filters:
    - type: ExtensionRef
      extensionRef:
        name: lambda-unwrap-transform
        group: gloo.solo.io
        kind: GlooTrafficPolicy
EOF

  5. Send a curl request to the unwrap-test function to check the response body format.

      curl $INGRESS_GW_ADDRESS:8080/unwrap-test -X POST
  
      curl localhost:8080/unwrap-test -X POST

    The response is unwrapped in the format required by AWS API gateways:

      {"TotalCodeSize":104330022,"FunctionCount":26}

Cleanup

You can optionally remove the resources that you set up as part of this guide.

  1. Delete the HTTPRoute, Backend, and GlooTrafficPolicy resources.

      kubectl delete HTTPRoute lambda-unwrap -n gloo-system
kubectl delete Backend lambda-unwrap -n gloo-system
kubectl delete GlooTrafficPolicy lambda-unwrap-transform -n gloo-system

  2. Use the AWS Lambda console to delete the unwrap-test function.