Containers, Pods, Clusters, and other Cloud-native Terminologies Explained for Novices
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For those accustomed to the cloud-native vocabulary, pods may not really mean the one which hold peas and containers may not refer to the ones found on a maritime ship. The same goes for orchestration and clusters. Although, in all the above cases, their functionalities do resemble their respective names and their purpose in real life. For instance, if the term ‘orchestration’ makes you picture the conductor who leads a musical ensemble, that’s actually right even in the case of a container orchestrator. A container orchestrator makes sure that all of the component pieces of a system “play” in the right place at the right time, and stop when they’re no longer needed. Let us learn all these terms in greater detail.
Let us begin with the term ‘container’. If by container you picturize those square wooden boxes stacked on a ship, then you are thinking in the right direction. These containers, like their real world counterparts, are meant to ‘contain’ an application or service and everything required for it to run, regardless of the external environment. By definition, a container is a package with the program to execute with all its dependencies, such as the code, runtime, system libraries, et cetera, all bound together in a box. A container may refer to two different things depending on the two states it assumes – rest and running. When at rest, a container is a file (or set of files) that is saved on disk. This is referred to as a Container Image or Container Repository. Once running, Containers are just a Linux process.
Now, these containers also need to be run in a proper order, which is where we need orchestration. Enter Kubernetes - one of the container orchestration tool by Google. Kubernetes enables you to automate, manage, and schedule applications defined by individual containers. Orchestration is what makes running and scaling containerized applications sustainable. A Kubernetes platform like Kubernetes lets an enterprise take advantage of numerous cloud solutions providers and grow as rapidly as required, without having to re-architect the entire infrastructure. This saves the need for significant deployment cycles and drastically improves the ability to provide new services as quickly as possible.
Unique Solutions provides containerization solutions in Kubernetes, Docker and other leading container platforms on all popular Linux environments. You can learn more about our offering of container as a service from our website.
Pods are the smallest, most basic deployable objects in Kubernetes. They’re essentially a wrapper (like a peapod) or housing for your individual containers when deploying them in Kubernetes. In a way, they can be imagined as containers holding your containers.
Now you may ask, “why would you need them if you already have containers?”
The quick answer is, when a Pod runs multiple containers, the containers can be managed as a single entity, where they can share resources and dependencies, communicate with one another, and coordinate when and how they are terminated. A Pod is meant to run a single instance of your application on your cluster.
A cluster can be thought of like a motherboard or circuit board that provides the circuitry to run all the pods in an orchestrated manner as defined by the users. A cluster is central to the basic architecture of Kubernetes: If you’re running Kubernetes, you’re running at least one cluster. There cannot be a Kubernetes deployment without a cluster.
All the above terms are interrelated in a manner that can be summarized as below:
- A container runs logically in a pod
- An orchestrator is required to run container(s)
- A group of pods run on a cluster.
- A cluster can contain many pods, related or unrelated [and] grouped under the tight logical borders called namespaces.
Understanding the terminology will provide you a deeper understanding of the underlying technologies. This will help you and your teams speak the same language with your cloud service provider and also provide insight into how to better architect your container environment for the goals you have.
Containers as a Service
Containers as a Service (Caas) is a model where IT organizations and developers can work together to build, ship and run their applications anywhere. CaaS enables an IT secured and managed application environment consisting of content and infrastructure, from which developers are able build and deploy applications in a self-service manner. You can get in touch with us for a hands on demo to explore Container as a service with Unique Solutions.