# Automating GitHub tasks (homebrew formula update)

**URL:** <https://discourse.nodered.org/t/automating-github-tasks-homebrew-formula-update/6106>\
**Category:** Share Your Projects\
**Created:** [23 December 2018 21:15 UTC](https://discourse.nodered.org/t/automating-github-tasks-homebrew-formula-update/6106 "2018-12-23T21:15:07Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![rusenask](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/rusenask/32/4580_2.png) [@rusenask](https://discourse.nodered.org/u/rusenask)\
**Post date:** [23 December 2018 21:15 UTC](https://discourse.nodered.org/t/automating-github-tasks-homebrew-formula-update/6106/1 "2018-12-23T21:15:07Z")

</div>

## Some background

While most of the people here seemed to be interested in home automation (me too, but just a little bit), I focus mostly on automating my ops tasks as a developer/engineer (updating cluster resources, for that I wrote [Keel](https://github.com/keel-hq/keel), updating CLI clients, manifests and anything else).

[Homebrew](https://brew.sh/) is a package manager for MacOS where anyone can create their application manifests for easy installation. However, there are multiple ways brew formulas can work, such as compiling during installation or downloading a binary. My method of installation is downloading a pre-compiled binary but I had to always remember to update the formula with the latest sha256 [https://github.com/webhookrelay/homebrew-tap/blob/master/relay.rb#L5](https://github.com/webhookrelay/homebrew-tap/blob/master/relay.rb#L5). If a newer version would be released without an update to this manifest, installation via homebrew would fail 🙂 Well, and there were times when I forgot that 😃

## Disclaimer

This flow is not directly reusable for you as it's working around my infrastructure. The purpose is to showcase some template generation, webhookrelay node and I also managed to find a problem in crypto node (more about it later).

## Stack

Node-RED on RPI with [node-red-contrib-webhookrelay](https://flows.nodered.org/node/node-red-contrib-webhookrelay) so I don't need to expose it to the internet, [GitHub account + node](https://flows.nodered.org/node/node-red-contrib-github) and Slack (that's really optional, but helpful as I push lots of updates to my Slack channel).

## The flow

The actual flow looks like this:

 ![node-red-brew-update](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/6/6b435f89ef8550d4f6a11b1ca663857e3893ea01.png)

I have uploaded flow here: [https://gist.github.com/rusenask/93ddb94479fbd6f1e3dcf3308da4ec1b](https://gist.github.com/rusenask/93ddb94479fbd6f1e3dcf3308da4ec1b).

1. Initially workflow is triggered by a build job that's being executed with [Google Cloud Builder](https://cloud.google.com/cloud-build/docs/) and webhook is dispatched through [this little application](https://github.com/webhookrelay/webhook-dispatcher)
2. Flow is triggered by a webhook to [webhookrelay.com](http://webhookrelay.com), [node here](https://flows.nodered.org/node/node-red-contrib-webhookrelay) which are then translated into node-red events.
3. It then downloads the binary and saves to the disk.
4. `sha256` custom function node is actually required due to a problem that I found with generating it via `node-red-contrib-crypto-js`. The problem I suspect was due to the way data is being fed into the crypto node (not in one go but with streams). Even setting it to 'one bytes buffer' it would still present a wrong sha. So, had to:

In settings.js enable `require`:

```json
    functionGlobalContext: {
        require: require
    },

```

And then read the file and calculate digest:

```auto
var require = global.get('require');
var crypto = require('crypto');
var fs = require('fs');

var algo = 'sha256';
var shasum = crypto.createHash(algo);

var file = '/tmp/relay-darwin-amd64-nr';
var s = fs.ReadStream(file);

s.on('data', function(d) { shasum.update(d); });
s.on('end', function() {
    var sum = shasum.digest('hex');
    node.send({payload: sum});
    
});

return;

```

1. Once we have the sha256 sum, we create two templates: one for GitHub brew formula template and one for Slack.
2. For Github we just do a simple overwrite since the file is quite small and only the sha sum ever changes.
3. As for Slack, I chose just to do a simple HTTP request with their incoming webhook integration as the available Slack node seemed a bit too heavyweight for such a tiny requirement. Have a look at the payload that needs to be sent:

```json
{
    "response_type": "in_channel",
    "text": "Brew formula SHA updated to: {{payload}}"
}

```

You could expand it to add pictures, buttons, attachments and so on, but in this case I just needed to see a notification.

## To sum up

So far I am really happy with Node-RED. Even though it would pretty pretty straightforward to just write everything in Go/JS/Python, for some reason it's more fun in Node-RED 🙂 I will be automating more and more side project tasks with it. Also, `function` node is a life saver!