In your journey of moving from virtual machines to containers, you first need to assess what can and can’t go in containers. Broadly speaking, there are two kinds of application workloads you can have – stateless and stateful. While stateless workloads do not store state and are computing powerhouses, such as APIs and functions, stateful applications, such as databases, require persistent storage to function.
Though it is possible to containerize any application that can run on a Linux virtual machine, stateless applications become the first low-hanging fruits you may want to look at. It is relatively easy to containerize these workloads because they don’t have storage dependencies. The more storage dependencies you have, the more complex your application becomes in containers.
Secondly, you also need to assess the form of infrastructure you want to host your applications on. For example, if you plan to run your entire tech stack on Kubernetes, you would like to avoid a heterogeneous environment wherever possible. In that scenario, you may also wish to containerize stateful applications. With web services and the middleware layer, most applications rely on some form of state to function correctly. So, in any case, you would end up managing storage.
Though this might open up Pandora’s box, there is no standard agreement within the industry regarding containerizing databases. While some experts are naysayers for its use in production, a sizeable population sees no issues. The primary reason is insufficient data to support or disprove using a containerized database in production.
I suggest that you proceed with caution regarding databases. While I am not opposed to containerizing databases, you must consider various factors, such as allocating proper memory, CPU, disk, and every dependency you have on virtual machines. Also, it would help if you looked into the behavioral aspects of the team. If you have a team of DBAs managing the database within production, they might not be very comfortable dealing with another layer of complexity – containers.
We can summarize these high-level assessment steps using the following flowchart:
Figure 1.9 – Virtual machine to container migration assessment
This flowchart accounts for the most common factors that are considered during the assessment. You also need to factor in situations that are unique to your organization. So, it is a good idea to take those into account as well before making any decisions.
