"Webhooks allow you to build or set up GitHub Apps which subscribe to certain events on GitHub.com. When one of those events is triggered, we'll send a HTTP POST payload to the webhook's configured URL"

This is a Fn function (written in Go) which acts as a GitHub webhook. Once configured and deployed

• it will be invoked in response to a new release in a GitHub repo

• and post release details (repo, version and access link) to Twitter

the function in this example is configured to respond to GitHub releases, but the same can be extended/applied to other events such as pull requests, commits etc.

To start with...

You will need

• Twitter account
• GitHub account

Twitter app setup

Follow these instructions. You'll need Consumer Key (API Key), Consumer Secret (API Secret), Access Token and Access Token Secret for your function

GitHub setup

Feel free to use an existing GitHub repository if you have one. I would recommend setting up a dummy repo to test things out

Deploy the function

• get latest and greatest Fn
  • Fn CLI - curl -LSs https://raw.githubusercontent.com/fnproject/cli/master/install | sh
  • Fn server - fn update server

Make sure you have Fn installed on a machine which can be accessed from public Internet (e.g. a VM), or use ngrok on your local machine to set up a secure tunnel to your localhost

• start Fn server - fn start
• clone this repo
• cd fn-github-webhook-twitter
• create the app - fn create app --config twitter_consumerkey=<twitter_consumerkey> --config twitter_consumersecret=<twitter_consumersecret> --config twitter_accesstoken=<twitter_accesstoken> --config twitter_accesstokensecret=<twitter_accesstokensecret> --config github_webhook_secret=<github_webhook_secret> fn-webhook-app

e.g. fn create app --config twitter_consumerkey=foo --config twitter_consumersecret=bar --config twitter_accesstoken=red-me --config twitter_accesstokensecret=s3cr3t --config github_webhook_secret=kehsihba fn-webhook-app

value for github_webhook_secret is used as the Secret for GitHub webhook configuration in next step (section)

• deploy the function - fn -v deploy --app fn-webhook-app --local

You should see an output similar to below..

...
Updating function github-release-handler using image github-release-handler:0.0.2...
Successfully created app:  fn-webhook-app
Successfully created function: github-release-handler with github-release-handler:0.0.2
Successfully created trigger: handle-release
Trigger Endpoint: http://localhost:8080/t/fn-webhook-app/handle-release

note down the Trigger Endpoint

Configure GitHub webhook

You can use the UI Settings > Webhooks section of your repository to get started - details in Github docs

We'll use the GitHub REST API for now

I used OAauth token over Basic Authentication via REST API. You can read up on this and more over here

Here is en example cURL command with the payload

curl -X POST -u <github_user_id>:<your_github_token_or_password> \
  https://api.github.com/repos/<github_user>/<github_repo>/hooks \
  -H 'content-type: application/json' \
  -d '{
  "name": "web",
  "active": true,
  "events": [
    "release"
  ],
  "config": {
    "url": "<fn_function_endpoint>",
    "secret": "<your_github_webhook_secret>",
    "content_type": "json",
    "insecure_ssl": 1
  }
}'

Replace the following parameters as per your setup

• github_user_id - user ID
• your_github_token_or_password - OAuth token or password
• github_user - user name
• github_repo - repository for which webhook is being configured
• your_github_webhook_secret - use the value which you used for github_webhook_secret while creating the function (fn create...)
• fn_function_endpoint - enter the Fn function trigger endpoint e.g. http://<your_fn_server_IP>:8080/t/fn-webhook-app/handle-release

Once completed, the new webhook should show up in the UI Settings > Webhooks section

Test

Create a release

We'll use the REST API

curl -X POST -u <github_user_id>:<your_github_token_or_password> \
  https://api.github.com/repos/<github_user>/<github_repo>/releases \
  -H 'content-type: application/json' \
  -d '{
  "tag_name": "v1.0.0",
  "target_commitish": "master",
  "name": "v1.0.0",
  "body": "Description of the release",
  "draft": false,
  "prerelease": false
}'

You should see the new release in the UI under https://github.com/<user>/<repo>/releases

Check twitter

You should see the tweet

Check GitHub

Under repo Settings > Webhooks, search the one you configured and see the Recent Deliveries section. You'll see a HTTP 200 (from Fn function) along with the tweet text

Problems

In case there is an issue with Twitter creds, tweets won't get posted. This will result in HTTP 500 from Fn function