Example hostname webhook

This is an example Webhook integration that shows how to pull hostnames from an external system to assign them to your Scalr servers.

This example webhook handler just generates a random string when Scalr requests a hostname. See the webhook.py file for additional details.

Setup instructions

The instructions below are written for RHEL 7 / Centos 7. Adapt as necessary for other distributions.

Webhook handler setup

Install the required packages:

yum install epel-release
yum install git gcc python python-devel python-pip uwsgi uwsgi-plugin-python

Retrieve the webhook code:

mkdir -p /opt/example-hostname-webhook
cd /opt/example-hostname-webhook
git clone https://github.com/scalr-integrations/example-hostname-webhook.git .

Install the Python dependencies

pip install -r requirements.txt

Configure uwsgi to serve the webhook

cp uwsgi.ini /etc/uwsgi.d/example-hostname-webhook.ini
chown uwsgi:uwsgi /etc/uwsgi.d/example-hostname-webhook.ini
systemctl enable uwsgi

Uwsgi will bind to 0.0.0.0 and serve the webhook on port 5008 by default. Edit the ini file to change this behaviour.

Scalr webhook setup

Log into Scalr at the global scope, and click on Webhooks in the main menu. In the Endpoints section, create a new endpoint with URL: http://<server-ip>:5008/hostname/

Note down the signing key that Scalr generated, we will need it later.

Webhook configuration

Edit the /etc/uwsgi.d/example-hostname-webhook.ini file and complete the env = SCALR_SIGNING_KEY statement with the Scalr signing key that Scalr generated.

Reload the configuration:

systemctl restart uwsgi

Testing and troubleshooting

The uwsgi logs are appended to /var/log/messages by default on centos 7.

To check that the web server is serving our webhook, run the following command on the webhook server:

curl -XPOST http://localhost:5008/hostname/

You should get a 403 error, because this request was not signed. If that is not the case, check for errors in the uwsgi logs.

Now to use this webhook to assign hostnames to some instances, go in a Farm's configuration. Click on a Farm Role, and in the Network tab, select "Webhook" as the hostname source. In the dropdown, select the endpoint you just created. Then save the Farm and launch it. Scalr will make a request to the webhook handler and assign the generated hostname to the instance.