Autoscaling using Callback

So far, we have looked at methods where we have invoked the templates manually. However, in a cloud infrastructure, we often scale infrastructure dynamically. As a result, executing jobs manually can be time-consuming. Ansible Tower provides us a way so that instances can call the jobs themselves without actually using the password. The concept where an instance calls up a job is called a Callback, so let's go ahead and create a Callback URL.

How to do it...

1. We should go to the Templates page and click on the name of the template.
2. Here, we need to scroll down to the options and check Allow Provisioning Callbacks.
3. We have to provide a config key. Ideally, this should be a long string. We can also click on the wand button next to the host config key to generate a random string, and then we can click on the SAVE button.

4. Any instance can call for the job using the Callback URL. Typically, this can be done through curl in /etc/rc.local, or by using the various mechanisms...