example for custom correlation with AppDynamics in Node.js

example-original.js

var argv = process.argv.slice(2);
var appd = require('appdynamics');

if (!(argv[0] === '-entry' || argv[0] === '-service')) {
    console.error('Please specify an -entry or -service role, e.g. `node example -entry`')
    process.exit(1);
}

/* Initialize App Dynamics */
appd.profile({
    debug: false,
    controllerHostName: 'localhost',
    controllerPort: 8090, 
    applicationName: 'microservices',
    tierName: 'tier' + argv[0],
    nodeName: 'node' + argv[0], // Node names must be unique. 
    controllerSslEnabled: false // Optional - use if connecting to controller via SSL
});

var EventEmitter = require('events').EventEmitter;
var redis = require('redis');
var publisherClient;
var subscriberClient;

function publish(channel, message, cb) {
    var client = publisherClient || (publisherClient = redis.createClient());

    client.publish(channel, JSON.stringify(message), cb);
}

function subscribe(channel) {
    var client = subscriberClient || (subscriberClient = redis.createClient());
    var emitter = new EventEmitter();

    client.on('message', function(messageChannel, message) {
        if (channel !== messageChannel) return;
        emitter.emit('message', JSON.parse(message));
    });

    client.subscribe(channel);
    return emitter;
}

function createEntry() {
    var publisherTopic = 'entry';
    var subscriberTopic = 'entry:response';
    var subscriber = subscribe(subscriberTopic);

    require('http').createServer(function(req, res) {

        /* Take next message */
        subscriber.once('message', function(message) {

            res.writeHead(message.statusCode);
            res.end(JSON.stringify(message));

        });

        var request = {
            at: new Date()
        };

        publish(publisherTopic, request, function(err) {
            if (err) console.error(err);
            console.log('requested');
        });
    }).listen(8080, function() {
        console.log('example listening on 8080');
    });
}

function createService() {
    var publisherTopic = 'entry:response';
    var subscriberTopic = 'entry';
    var subscriber = subscribe(subscriberTopic);

    subscriber.on('message', function(message) {
        console.log('received', message);


        var response = {
            statusCode: 200,
            dates: [message.at, new Date()]
        };

        publish(publisherTopic, response, function(err) {
            if (err) console.error(err);
            console.log('responded');
        });
    });
}

if (argv[0] === '-entry') createEntry();
else if (argv[0] === '-service') createService();

function noop(){}

example.js

var argv = process.argv.slice(2);
var appd = require('appdynamics');

if (!(argv[0] === '-entry' || argv[0] === '-service')) {
    console.error('Please specify an -entry or -service role, e.g. `node example -entry`')
    process.exit(1);
}

/* Initialize App Dynamics */
appd.profile({
    debug: false,
    controllerHostName: 'localhost',
    controllerPort: 8090, 
    applicationName: 'microservices',
    tierName: 'tier' + argv[0],
    nodeName: 'node' + argv[0], // Node names must be unique. 
    controllerSslEnabled: false // Optional - use if connecting to controller via SSL
});

var EventEmitter = require('events').EventEmitter;
var redis = require('redis');
var publisherClient;
var subscriberClient;

function publish(channel, message, cb) {
    var client = publisherClient || (publisherClient = redis.createClient());

    client.publish(channel, JSON.stringify(message), cb);
}

function subscribe(channel) {
    var client = subscriberClient || (subscriberClient = redis.createClient());
    var emitter = new EventEmitter();

    client.on('message', function(messageChannel, message) {
        if (channel !== messageChannel) return;
        emitter.emit('message', JSON.parse(message));
    });

    client.subscribe(channel);
    return emitter;
}

function createEntry() {
    var publisherTopic = 'entry';
    var subscriberTopic = 'entry:response';
    var subscriber = subscribe(subscriberTopic);

    require('http').createServer(function(req, res) {
        var trx = appd.startTransaction(req);
	trx.beforeExitCall = function getExitInfo(exitCall) { //Suppress default Redis exit handling
	if (exitCall.backendName == 'Redis')
	    return;
	else
	    return exitCall;
	}

        /* Take next message */
        subscriber.once('message', function(message) {
	    if (message.ci) {
		var nci = appd.parseCorrelationInfo(message.ci);
		var trx = appd.startTransaction(nci);
	    }

            res.writeHead(message.statusCode);
            res.end(JSON.stringify(message));

	    if (message.ci) trx.end();
        });

        var exit = trx.startExitCall({ // Inform AppD of upcoming exit call
            exitType: 'EXIT_CACHE',
            label: 'Event Bus - ' + publisherTopic,
            identifyingProperties: { // together, properties must uniquely identify the message destination
                bus: "local_redis",
                topic: publisherTopic
            }
        });

        var request = {
            ci: trx.createCorrelationInfo(exit), // put the AppD correlation header into the message payload
            at: new Date()
        };

        publish(publisherTopic, request, function(err) {
            if (err) console.error(err);
            console.log('requested');
            trx.endExitCall(exit); // Inform AppD that exit call has completed
            trx.end();
        });
    }).listen(8080, function() {
        console.log('example listening on 8080');
    });
}

function createService() {
    var publisherTopic = 'entry:response';
    var subscriberTopic = 'entry';
    var subscriber = subscribe(subscriberTopic);

    subscriber.on('message', function(message) {
        console.log('received', message);
        if (!message.ci) return publish(publisherTopic, { statusCode: 400, info: 'CorrelationInfo is empty.' }, noop);

        var nci = appd.parseCorrelationInfo(message.ci);
        var trx = appd.startTransaction(nci); // Associate transaction as downstream component of txn defined in ci field (upstream correlato  header)
    
	trx.beforeExitCall = function getExitInfo(exitCall) { // Supress default Redis exit handling
	    if (exitCall.backendName == 'Redis')
		return;
	    else
		return exitCall;
	} 


        var exit = trx.startExitCall({
            exitType: 'EXIT_CACHE',
            label: 'Event Bus - ' + publisherTopic,
            identifyingProperties: { // together, properties must identify the message destination
                bus: "local_redis",
                topic: publisherTopic
            }
        });

        var response = {
	    ci: trx.createCorrelationInfo(exit), // ci is correlation header for reply message
            statusCode: 200,
            dates: [message.at, new Date()]
        };

        publish(publisherTopic, response, function(err) {
            if (err) console.error(err);
            console.log('responded');
	    trx.endExitCall(exit); // Inform AppD that exit call is over
            trx.end();
        });
    });
}

if (argv[0] === '-entry') createEntry();
else if (argv[0] === '-service') createService();

function noop(){}

Node-example

The 2 other files in this gist show a Redis request/response example (example-original.js)
and the same file modified for instrumentation with AppDynamics (example.js)