@webscale-networks/cloudedge-handlers/execution_context/lambda/src/index.js

Webscale Networks CloudEDGE Handlers for cloud-agnostic edge function execution

'use strict';
const fs = require('fs');
const path = require('path');
const _ = require('lodash');

const handlers = require('../../utils/src/handlers.js');
const utils = require('./utils.js');

// event is an Lambda@Edge event. Lambda@Edge supports 'viewer-request',
// 'viewer-response', 'origin-request' and 'origin-response'. The structure of
// this object is outlined here: https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/lambda-event-structure.html.
exports.handler = async (event, _context) => {
    const rawHandlers = fs.readFileSync(
        path.resolve( __dirname, '../../../handlers.json'),
    );
    const config = JSON.parse(rawHandlers);

    // Convert request into generic Webscale object.
    const clonedEvent = _.cloneDeep(event);
    const wReq = utils.originToWebscaleRequest(
        clonedEvent.Records[0].cf.config,
        clonedEvent.Records[0].cf.request,
    );

    // Determine the handler that is configured to handle each event and call it.
    let result = null;
    if (utils.eventType(clonedEvent) == 'origin-request') {
        if (config['requestHandlers']) {
            result = await handlers.run(
                wReq, null, config['requestHandlers'], config,
            );
        } else {
            console.log('Origin request handler not specified.');
            return clonedEvent.Records[0].cf.request;
        }
    } else if (utils.eventType(clonedEvent) == 'origin-response') {
        if (config['responseHandlers']) {
            const wResp = utils.originToWebscaleResponse(
                clonedEvent.Records[0].cf.config,
                clonedEvent.Records[0].cf.response,
            );
            result = await handlers.run(
                wReq, wResp, config['responseHandlers'], config,
            );
        } else {
            console.log('Origin response handler not specified.');
            return clonedEvent.Records[0].cf.response;
        }
    }

    if (isSet(result)) {
        if (result.error) {
            if (result.response) {
                return utils.webscaleToOriginResponse(result.response);
            } else {
                return utils.defaultErrorResponse(
                    _.get(clonedEvent, 'Records[0].cf.response.headers'),
                );
            }
        } else if (result.response) {
            return utils.webscaleToOriginResponse(result.response);
        } else {
            return utils.webscaleToOriginRequest(result.request);
        }
    } else {
        if (utils.eventType(clonedEvent).endsWith('request')) {
            console.log(
                'The handler did not return a result, sending back original request: ',
                clonedEvent.Records[0].cf.request,
            );
            return clonedEvent.Records[0].cf.request;
        } else {
            console.log(
                'The handler did not return a result, sending back original response: ',
                clonedEvent.Records[0].cf.response,
            );
            return clonedEvent.Records[0].cf.response;
        }
    }
};

const isSet = (result) => {
    return result &&
        (_.has(result, 'error') ||
          _.has(result, 'response') ||
          _.has(result, 'request'));
};