Example Node.JS Lambda@Edge blue/green deployment using featureflow

A simple application written in Node.JS with the serverless framework and featureflow that runs on AWS Lambda@Edge.

This application uses featureflow to redirect the user to one endpoint or another based on header values.

See in action at https://www.youtube.com/watch?v=VbcLbwJirGo

Requirements

• An AWS account that is set up
• A cloudfront distribution (as we would like to trigger it on origin-response)
• Serverless framework

IAM Role for the function

The function has a very basic IAM role set up that will be created by serverless. The role has access to write to CloudWatch logs and it can be assumed by lambda and edgelambda services. For production, the logs should be more restrictive than the AWS managed AWSLambdaBasicExecutionRole.

Set your environment SDK key

Replace {apiKey: 'sdk-srv-env-YOUR-KEY'} in handler.js with your Server Environment SDK Key.

If you don't have a featureflow account - head to https://app.featureflow.io and sign up, it only takes 1 minute.

How to deploy

Set up a profile that has access to create cloudformation templates, access S3 etc. Please check the relevant documentation of serverless.

serverless deploy --aws-profile=my-profile-name

The command above will deploy the lambda function. For Lambda@Edge it is important to deploy to us-east-1 as that is where the function will be distributed to CloudFront.

Test

In the lambda view click 'test' and create an event, for example:

{
  "Records": [
    {
      "cf": {
        "config": {
          "distributionId": "EXAMPLE"
        },
        "request": {
          "uri": "/",
          "method": "GET",
          "clientIp": "2001:cdba::3257:9652",
          "headers": {
            "cloudfront-viewer-country": [
              {
                "key": "US",
                "value": "US"
              }
            ],
            "x-cohort": [
              {
                "key": "beta",
                "value": "beta"
              }
            ],            
            "user-agent": [
              {
                "key": "User-Agent",
                "value": "Test Agent"
              }
            ],
            "host": [
              {
                "key": "Host",
                "value": "d123.cf.net"
              }
            ],
            "cookie": [
              {
                "key": "Cookie",
                "value": "SomeCookie=1; AnotherOne=A; X-Experiment-Name=B"
              }
            ]
          }
        }
      }
    }
  ]
}

Trigger from CloudFront

On the AWS console for Lambda, find the function and click on Deploy to Lambda@Edge.

On the next screen you will need to select which distribution you are deploying to and on which event, select viewer request event.

Viewer request is evaluated before the cache is hit, otherwise the cache would continue to return with the first evaluated variant.

First step

Second step

After the function is deployed make a request to the cloudfront url, you should be redirected to the failover endpoint.

Note that the logs will be written to a region that is close to the CDN edge node that is serving you. For example even though the Lambda is in us-east-1 it is now deployed throughout the distribution and if you are in France for example the logs of the edge function will be written to the Paris region.

Configure featureflow

Create a feature in the featureflow console with a matching key (for example lambda-redirect)

If you wish, you can create custom variants to better reflect your redirect rules:

Then you can target the variants using rules based on the user attributes obtained from the header and cookie values:

See https://docs.featureflow.io/using-featureflow-with-aws-lambda for more details.

See https://www.youtube.com/watch?v=VbcLbwJirGo for a 2-minute video example