lambda-edge-router.js

'use strict'

/* This list may be incomplete or outdated! It may be best to integrate with an external service to obtain these values */
const eu_country_codes = ['BE','BG','CZ','DK','DE','EE','IE','EL','ES','FR','HR','IT','CY','LV','LT','LU','HU','MT','NL','AT','PL','PT','RO','SI','SK','FI','SE','UK']

const us_origin_domain = 'ec2-54-166-49-18.compute-1.amazonaws.com'
const eu_origin_domain = 'ec2-34-244-9-66.eu-west-1.compute.amazonaws.com'

/* This is an origin request function */
exports.handler = (event, context, callback) => {
    console.log(`edge-router processing request:\n${JSON.stringify(event, null, 2)}`)
    
    if(!request.origin.custom){
       return callback(`Request  did not contain a custom origin: ${JSON.stringify(event, null, 2)}`)
    }
    
    const request = event.Records[0].cf.request
    const headers = request.headers
    
    /*
     * Based on the value of the CloudFront-Viewer-Country header, direct the user to a regional origin.
     * NOTE: 1. You must configure your distribution to cache based on the
     *          CloudFront-Viewer-Country header. For more information, see
     *          http://docs.aws.amazon.com/console/cloudfront/cache-on-selected-headers
     *       2. CloudFront adds the CloudFront-Viewer-Country header after the viewer
     *          request event. To use this example, you must create a trigger for the
     *          origin request event.
     */
   
    if (headers['cloudfront-viewer-country']) {
        const countryCode = headers['cloudfront-viewer-country'][0].value
        console.log(`cloudfront-viewer-country: ${countryCode}`)
        
        request.origin.custom.domainName = us_origin_domain

        if(eu_country_codes.includes(countryCode)){
            console.log(`EU country code detected`)
            request.origin.custom.domainName = eu_origin_domain
        }
        
        console.log(`modified request:\n${JSON.stringify(request, null, 2)}`)
    }
    
    callback(null, request)
}

Related documentation:

• https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/lambda-event-structure.html