concept multiple process in category kubernetes

This is an excerpt from Manning's book Kubernetes in Action, Second Edition MEAP V05. Login to get full access to this book.

Let’s discuss why we need to run multiple containers together, as opposed to, for example, running multiple processes in the same container.

This is an excerpt from Manning's book Kubernetes in Action. Login to get full access to this book.

Scaling microservices, unlike monolithic systems, where you need to scale the system as a whole, is done on a per-service basis, which means you have the option of scaling only those services that require more resources, while leaving others at their original scale. Figure 1.2 shows an example. Certain components are replicated and run as multiple processes deployed on different servers, while others run as a single application process. When a monolithic application can’t be scaled out because one of its parts is unscalable, splitting the app into microservices allows you to horizontally scale the parts that allow scaling out, and scale the parts that don’t, vertically instead of horizontally.

Figure 3.4. A container shouldn’t run multiple processes. A pod shouldn’t contain multiple containers if they don’t need to run on the same machine.

Understanding why multiple containers are better than one contain- ner running multiple processes

Imagine an app consisting of multiple processes that either communicate through IPC (Inter-Process Communication) or through locally stored files, which requires them to run on the same machine. Because in Kubernetes you always run processes in containers and each container is much like an isolated machine, you may think it makes sense to run multiple processes in a single container, but you shouldn’t do that.