Chapter 7. Container Orchestration

Throughout this book, you ran many different Docker containers on your development machine. Each time that you ran them, you did so using the same mechanism: manually running docker commands in your terminal. Of course, this is fine for doing local development, and perhaps it can be used to run a single service instance in production, but when it comes to running an entire fleet of services, this approach is going to get rough.

This is where a container orchestration tool comes into play. Loosely put, a container orchestration tool manages the lifetimes of many ephemeral containers. Such a tool has many unique responsibilities and must take into consideration situations like the following:

• Containers need to scale up and down as load increases and decreases.

• New containers are occasionally added as additional services are created.

• New versions of containers need to be deployed to replace old versions.

• A single machine may not handle all the containers required by an organization.

• Like-containers should be spread across multiple machines for redundancy.

• Containers should be able to communicate with one another.

• Incoming requests for like-containers should be load balanced.

• If a container is deemed unhealthy, it should be replaced by a healthy one.

Container orchestration works great with stateless services, like a typical Node.js service where instances can be destroyed or re-created without having many side effects. Stateful ...