Deployment strategies

We have seen how to distribute software in your environment, let's now speak about deployment strategies; that is how to upgrade your application without your service suffering from it.

There are three different problems you might incur during an update:

• Downtime during the update rollout
• The new version has problems
• The new version seems to work, until it fails

The first problem is known to every system administrator. During the update, you are probably going to restart some services, and for the time between the stop and the start of the service, your application will not be available on that machine. To avoid this also means that your application is not available at all; you will need to have at least some machines with the application available and a smart load balancer in front that will remove (and add them back when is the case) all nonfunctioning nodes.

The second problem can be prevented in multiple ways. The cleanest one would be testing in the CI/CD pipeline...