adds an AWS X-Ray subsegment and Metadata for an Alexa Skills Kit triggered Lambda

aws-xray-utils.js

'use strict';

// http://docs.aws.amazon.com/lambda/latest/dg/lambda-x-ray.html
/*
 * expected usage:

    let AWS = require('aws-sdk');
    const AWSXRay = require('aws-xray-sdk-core');
    const AWSXRayUtil = require('./aws-xray-utils');
    if (process.env.AWS_XRAY_DAEMON_ADDRESS) {
        // detect AWS X-Ray
        AWS = AWSXRay.captureAWS(AWS);
    }

    const Alexa = require("alexa-sdk");

    var handler = function(event, context, callback) {
        const alexa = Alexa.handler(event, context, callback);
        alexa.appId = appId;
        alexa.dynamoDBTableName = dynamoDBTableName;
        alexa.registerHandlers(handlers, resetHandlers);
        alexa.execute();
    };

    if (AWSXRay) {
        handler = AWSXRayUtil.captureLambdaHandler(handler);
    }

    exports.handler = handler;
*/

const AWSXRay = require('aws-xray-sdk-core');

exports.captureLambdaHandler = function(handler) {
    if (!typeof handler === 'function') {
        throw new Error('handler is not a function');
    }

    let subsegment = null;
    const wrappedFunction = function(event, context, callback) {
        if (process.env.AWS_XRAY_DAEMON_ADDRESS) {
            // need subsegment because of following error
            // Function "addMetadata" cannot be called on an AWS Lambda segment.
            // Please use a subsegment to record data.
            const segmentName = process.env._HANDLER || 'index.handler';
            subsegment = AWSXRay.getSegment().addNewSubsegment(segmentName);
            subsegment.addMetadata('event', event);
            subsegment.addMetadata('context', context);
            if (context.awsRequestId) {
                subsegment.addAnnotation('awsRequestId', context.awsRequestId);
                console.log(`AWS X-Ray filter:  Annotation.awsRequestId = "${context.awsRequestId}"`);
            }
            if (event && event.request && event.request.error) {
                subsegment.addError(event.request.error, false);
                console.log(`ERROR:  ${JSON.stringify(event.request.error)}`);
            }

            // TODO: inspect event to ensure Alexa Skills Kit trigger
            addAlexaSkillsKitAnnotations(subsegment, event);
        }
        try {
            handler(event, context, function(err, result) {
                callback(err, result);
                if (subsegment) {
                    subsegment.addMetadata('result', result);
                    subsegment.close(err, false);
                }
            });
        } catch (e) {
            if (subsegment) {
                subsegment.close(e, false);
            }
        }
    };

    return wrappedFunction;
};

function addAlexaSkillsKitAnnotations(subsegment, event) {
    if (event.session) {
        subsegment.addAnnotation('sessionId', event.session.sessionId);
        if (event.session.new == true) {
            console.log(`AWS X-Ray filter:  Annotation.sessionId = "${event.session.sessionId}"`);
        }
    }

    if (event.context) {
        subsegment.addAnnotation('applicationId', event.context.System.application.applicationId);
        subsegment.addAnnotation('userId', event.context.System.user.userId);
    }

    if (event.request) {
        subsegment.addAnnotation('requestId', event.request.requestId);
        subsegment.addAnnotation('type', event.request.type);
        if (event.request.intent) {
            subsegment.addAnnotation('intent', event.request.intent.name);
        }
    }
}