Origin Request lambda@edge function for cookie and header evaluation

cf-origin-switch-cookie-and-header_origin-request.js

'use strict';

const AWS = require('aws-sdk');
const ssm = new AWS.SSM({ region: 'eu-central-1' });


const SOURCE_HEADER_NAME = 'x-myapp-origin';
const LATEST_ORIGIN_GIT_HASH = 'myapp_latest-origin-git-hash'


exports.handler = async event => {
    console.group('[INFO] lambda@edge Origin Request')
    const request = event.Records[0].cf.request;

    if (request.headers[SOURCE_HEADER_NAME]) {
        const headerValue = request.headers[SOURCE_HEADER_NAME][0].value;
        const domainName = `web-bucket-${headerValue}.s3.eu-central-1.amazonaws.com`;

        console.log(`[OVERWRITE] Using custom origin: ${domainName}`);

        request.origin = {
            s3: {
                ...request.origin.s3,
                domainName,
            },
        };

        request.headers['host'] = [{ key: 'Host', value: domainName }];

        console.log(request.origin.s3);
        console.log(request.headers.host);
    } else {
        const latestOriginHash = await ssm.getParameter({
            Name: LATEST_ORIGIN_GIT_HASH,
            WithDecryption: false,
          }).promise();
      
          const hash = latestOriginHash.Parameter.Value;
      
          const domainName = `web-bucket-${hash}.s3.eu-central-1.amazonaws.com`;
          console.log(`[LATEST] Using origin: ${domainName}`);
      
          request.origin = {
            s3: {
              ...request.origin.s3,
              domainName,
            },
          };
      
          request.headers[ 'host' ] = [{ key: 'Host', value: domainName }];
    }

    console.groupEnd()

    return request;
};