How to test 3rd party hooks and webservices locally

In the past few months I have spent a bit of my spare time helping the Namshi team build a very small NodeJS app to trigger builds of our projects through Github.

The main idea is that when someone pushes changes to one of the github repos, we’d want to build a new docker image with that code and push it to our private registry¹.

After laying down most of the app, time had come to test the integration with Github’s hooks, and I was left wondering how easy it would have been to test this on my local machine, without having to deploy the app somewhere where it would be publicly accessible.

ngrok to the rescue

Turns out that Github has a very good tutorial on how to test hooks locally through a very interesting software, ngrok.

Ngrok tunnels traffic from the internet to your local machine through some black magic. Just download it and create a sample NodeJS server on your machine:

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require('http').createServer(function(req, res){
  res.writeHead(200, {});
  res.end('Hello');
}).listen(8888);

Running it through node server.js will, of course, make it accessible at localhost:8888.

Now, the magic: run ./path/to/ngrok http 8888 and ngrok will tell you at what public address your server is now available:

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ngrok by @inconshreveable                                                                                                                                                                    (Ctrl+C to quit)

Tunnel Status                 online
Version                       2.0.19/2.0.19
Web Interface                 http://127.0.0.1:4040
Forwarding                    http://b8b939d0.ngrok.io -> localhost:8888
Forwarding                    https://b8b939d0.ngrok.io -> localhost:8888

Connections                   ttl     opn     rt1     rt5     p50     p90
                              1       1       0.01    0.00    59.49   59.49

Open http://xxxx.ngrok.io (of course, the address / hash will be different everytime you launch ngrok) and you will now be able to access your local service from the internet.

Icing on the cake: now, to test your application, you can simply point the github hook to xxxx.ngrok.io and receive hooks on your local machine.