Effective DevOps with AWS

Canary-testing changes

One of the great benefits of using Ansible to manage services is that you can easily make changes to your code and quickly push the change. In some situations where you have a big fleet of services managed by Ansible, you may wish to push out a change just to a single host to make sure things are how you expect them to be. This is often called canary testing. With Ansible, doing that is really easy. To illustrate that, we are going open the file roles/helloworld/files/helloworld.js and then simply change the response on Line 11 from Hello World to Hello New World:

    // Send the response body as "Hello World" 
    response.end('Hello New World\n'); 
}).listen(3000); 

Save the file. Then run ansible-playbook again, first with ...