Transform responses

Configure the control plane to wrap the request to or unwrap the response from an AWS Lambda as if the gateway proxy is an AWS API Gateway.

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 Solo Enterprise for kgateway 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 Solo Enterprise for kgateway.

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

   notifications

   Make sure to add the payloadTransformMode: None setting to your Backend. By default, the payload transformation mode is set to Envoy, which automatically transforms the payload. To prevent double transformation for AWS Lambdas later, change this setting to None.

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

3. Create an HTTPRoute resource that references the lambda-unwrap Backend and the lambda-unwrap-transform EnterpriseKgatewayTrafficPolicy.

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

4. Before you apply the transformation policy, send a curl request to the unwrap-test function to check the raw response format.

   curl $INGRESS_GW_ADDRESS:8080/unwrap-test -H "Host: lambda.${AWS_LAMBDA_REGION}.amazonaws.com"

   curl localhost:8080/unwrap-test -H "Host: lambda.${AWS_LAMBDA_REGION}.amazonaws.com"

   Example raw response:

   {"statusCode":201,"headers":{"key":"value"},"isBase64Encoded":false,"multiValueHeaders":{"X-Custom-Header":["My value","My other value"]},"body":"{\"TotalCodeSize\":104330022,\"FunctionCount\":26}"}

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

   kubectl apply -f - <<EOF
   apiVersion: enterprisekgateway.solo.io/v1alpha1
   kind: EnterpriseKgatewayTrafficPolicy
   metadata:
     name: lambda-unwrap-transform
     namespace: kgateway-system
   spec:
     targetRefs:
     - group: gateway.networking.k8s.io
       kind: HTTPRoute
       name: lambda-unwrap
     entTransformation:
       awsLambda:
         requestFormat: APIGateway
         responseFormat: APIGateway
   EOF

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

   curl $INGRESS_GW_ADDRESS:8080/unwrap-test -H "Host: lambda.${AWS_LAMBDA_REGION}.amazonaws.com"

   curl localhost:8080/unwrap-test  -H "Host: lambda.${AWS_LAMBDA_REGION}.amazonaws.com"

   The response is now 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 EnterpriseKgatewayTrafficPolicy resources.

   kubectl delete HTTPRoute lambda-unwrap -n kgateway-system
   kubectl delete Backend lambda-unwrap -n kgateway-system
   kubectl delete EnterpriseKgatewayTrafficPolicy lambda-unwrap-transform -n kgateway-system

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