Hands-on:Optimizing Forex Trading Application with Lambda@Edge and Origin Failover in AWS

To implement the solution using AWS CLI or Boto3 with Lambda@Edge for optimizing the forex trading application and adding an origin failover for improved availability, follow these steps:

Step 1: Create Lambda Functions

You’ll need to create Lambda functions to customize the content and perform the authentication process. One function will be for content customization, and another will be for authentication. You can use the AWS CLI or AWS Lambda Console to create these functions. Make sure they are associated with the appropriate IAM roles with the necessary permissions.

Step 2: Configure Lambda@Edge

Now, use AWS CLI or Boto3 to configure Lambda@Edge in your CloudFront distribution to execute these Lambda functions on viewer requests. Specifically, you want to set up the functions to optimize the login process.

Here’s an example AWS CLI command to create an association between a Lambda function and a CloudFront distribution. You would need to customize this according to your specific use case:

aws cloudfront create-distribution --distribution-config file://cloudfront-distribution-config.json

In cloudfront-distribution-config.json, you should configure the LambdaFunctionAssociations section to associate the Lambda functions with specific CloudFront events. For example:

"LambdaFunctionAssociations": {
  "Quantity": 2,
  "Items": [
    {
      "EventType": "viewer-request",
      "LambdaFunctionARN": "arn:aws:lambda:your-region:your-account-id:function:content-customization-lambda"
    },
    {
      "EventType": "viewer-request",
      "LambdaFunctionARN": "arn:aws:lambda:your-region:your-account-id:function:authentication-lambda"
    }
  ]
}

Step 3: Set Up Origin Failover

To configure an origin failover, you should first create a CloudFront distribution configuration with multiple origins. One will be the primary origin, and the other will be the secondary origin.

Here’s an example AWS CLI command to create a CloudFront distribution with origin failover:

aws cloudfront create-distribution --distribution-config file://cloudfront-distribution-config.json

In cloudfront-distribution-config.json, configure the Origins section with your primary and secondary origins. For example:

"Origins": {
  "Quantity": 2,
  "Items": [
    {
      "Id": "primary-origin",
      "DomainName": "primary-origin.example.com",
      "CustomOriginConfig": {
        "HTTPPort": 80,
        "HTTPSPort": 443,
        "OriginKeepaliveTimeout": 5
      }
    },
    {
      "Id": "secondary-origin",
      "DomainName": "secondary-origin.example.com",
      "CustomOriginConfig": {
        "HTTPPort": 80,
        "HTTPSPort": 443,
        "OriginKeepaliveTimeout": 5
      }
    }
  ]
}

In addition, configure the OriginGroups section to set up failover behavior:

"OriginGroups": {
  "Quantity": 1,
  "Items": [
    {
      "Id": "my-origin-group",
      "FailoverCriteria": {
        "StatusCodes": {
          "Items": [502, 503, 504],
          "Quantity": 3,
          "Enabled": true
        }
      },
      "Members": {
        "Items": [
          {
            "OriginId": "primary-origin"
          },
          {
            "OriginId": "secondary-origin"
          }
        ]
      }
    }
  ]
}

This configuration specifies that CloudFront will switch to the secondary origin when HTTP status codes 502, 503, or 504 are returned from the primary origin.

Step 4: Update DNS

Finally, update your DNS settings to point to your CloudFront distribution, and users should start experiencing the improved login times and failover capabilities.

Remember to replace placeholders like your-region, your-account-id, content-customization-lambda, authentication-lambda, primary-origin.example.com, and secondary-origin.example.com with actual values from your AWS environment.

To determine whether CloudFront, a VPC (Virtual Private Cloud), or an ELB (Elastic Load Balancer) is closer to the user in an AWS Lambda@Edge function, you can analyze the event object in the Lambda function, which contains information about the viewer request. Specifically, you can check the event['Records'][0]['cf']['config']['distributionDomainName'] to identify whether CloudFront is in use. If you need to determine whether the request originated from within a VPC or if an ELB is involved, you can analyze the event['Records'][0]['cf']['request']['origin']['s3'] configuration. Here’s how you can approach this:

def lambda_handler(event, context):
    # Check if the request is coming through CloudFront
    distribution_domain_name = event['Records'][0]['cf']['config']['distributionDomainName']

    if distribution_domain_name:
        # The request is coming through CloudFront
        # You can include logic specific to CloudFront here
        return {
            'statusCode': 200,
            'body': 'Request is coming through CloudFront.'
        }
    else:
        # The request is not coming through CloudFront
        # Check if the request is coming through an ELB or within a VPC
        s3_origin_info = event['Records'][0]['cf']['request']['origin']['s3']

        if 'customHeaders' in s3_origin_info:
            # The request is coming through an Elastic Load Balancer (ELB)
            # You can include logic specific to ELB here
            return {
                'statusCode': 200,
                'body': 'Request is coming through an ELB.'
            }
        else:
            # The request is not coming through CloudFront or an ELB
            # You can assume it's coming directly or within a VPC
            # Include logic specific to VPC or direct request here
            return {
                'statusCode': 200,
                'body': 'Request is coming through a VPC or directly.'
            }

In this example, we first check whether the request is coming through CloudFront by inspecting the distributionDomainName. If it is present, we know it’s a CloudFront request.

If the request is not coming through CloudFront, we further inspect the s3_origin_info. If it contains a customHeaders field, it’s indicative of a request passing through an Elastic Load Balancer (ELB). Otherwise, you can assume that the request is either coming directly or within a VPC.

Keep in mind that this is a simplified approach and may not cover all possible scenarios. The actual structure of the event object and the behavior of your application may vary based on your specific configuration. It’s crucial to adjust the logic to match your use case.

You can use custom headers in AWS CloudFront to route users to a specific Elastic Load Balancer (ELB) or Virtual Private Cloud (VPC) by configuring CloudFront with Lambda@Edge functions. This approach allows you to inspect custom headers in viewer requests and route the requests based on the headers’ values. Here’s a general outline of the steps to achieve this:

1. Create an AWS Lambda Function: Create an AWS Lambda function that inspects the custom headers and determines the target destination (ELB or VPC) based on the header values. This Lambda function will be executed on CloudFront’s “viewer request” event. Here’s a basic Python example:

   import json

   def lambda_handler(event, context):
       request = event['Records'][0]['cf']['request']
       headers = request['headers']

       if 'X-Routing-Header' in headers:
           routing_value = headers['X-Routing-Header'][0]['value']
           if routing_value == 'ELB':
               request['origin']['custom']['customHeaders']['Host'] = ['your-elb-hostname']
           elif routing_value == 'VPC':
               request['origin']['custom']['customHeaders']['Host'] = ['your-vpc-internal-dns']

       return request

2. Create a CloudFront Distribution: Create a new CloudFront distribution or update an existing one to use the Lambda function for “viewer request” processing. This is done in the CloudFront distribution settings under “Lambda Function Associations.”
3. Set Up Custom Headers in Viewer Requests: Modify your web application to include custom headers in viewer requests. In this example, the X-Routing-Header custom header is used to specify the target destination (ELB or VPC). You can set this header in your web application or use an application firewall or middleware to insert it.
4. Routing Logic: In the Lambda function, based on the value of the X-Routing-Header custom header, you can set the Host header to route the request to the specified destination. In the example, if the header value is ‘ELB’, it routes to the ELB hostname. If the header value is ‘VPC’, it routes to the VPC’s internal DNS. Ensure that the host names (your-elb-hostname and your-vpc-internal-dns) are correctly configured in your setup.
5. Deploy and Test: Deploy the Lambda function and update your CloudFront distribution. Test the routing functionality by sending requests with the custom header.

This approach allows you to route users to different destinations based on custom header values. Keep in mind that this is a simplified example, and in a real-world scenario, you should handle error handling, security, and validation as needed for your specific use case.