What Is Kubernetes ?

Kubernetes is an open-source container orchestration system for automating the deployment, scaling, and management of containerized applications. It was originally developed by Google, and is now maintained by the Cloud Native Computing Foundation (CNCF).

Kubernetes is designed to work with a variety of container runtimes, such as Docker, but it is not limited to them. It provides a unified way to manage and orchestrate containers, regardless of the underlying infrastructure. This makes it an ideal choice for organizations that are looking to adopt container-based infrastructure and take advantage of the benefits of containers, such as increased efficiency, scalability, and portability.

Kubernetes works by using a cluster of nodes, each of which runs a container runtime and the Kubernetes components necessary to manage the containers. The cluster is managed by a set of control plane components, including the etcd key-value store, which stores the configuration data for the cluster, and the API server, which exposes a RESTful API that can be used to interact with the cluster.

At the core of Kubernetes is the concept of a “pod,” which is the smallest and simplest unit in the Kubernetes object model. A pod represents a single instance of a running process in a container, and can contain one or more containers. Pods are used to group together related containers and provide them with shared resources, such as network and storage.

Once the pods are created, they can be managed and orchestrated using a variety of Kubernetes objects, such as Replication Controllers, which are used to ensure that a specified number of replicas of a pod are running at any given time, and Services, which provide a stable endpoint for accessing a set of pods.

Kubernetes also provides built-in support for load balancing and automatic scaling of the application. It can automatically distribute the load between the different pods, and scale the number of replicas up or down based on the demand.

In addition, Kubernetes provides a number of features that make it easy to deploy and manage applications in a production environment. For example, it includes built-in support for rolling updates, which allow you to update the application and its components without any downtime. It also provides configurable security options, such as role-based access control, to ensure that your cluster is secure and that only authorized users can access it.

Overall, Kubernetes is a powerful and flexible platform for managing containerized applications, and its popularity continues to grow as more and more organizations adopt containers as a key part of their infrastructure. It can be used on different cloud providers, on premise and even on your local computer with Minikube.

Please note that this is just a high level overview of Kubernetes, and there is much more to learn and explore in terms of its features and capabilities.

Kubernetes Objects

Kubernetes objects are the basic building blocks of a Kubernetes cluster. They represent the state of the system and are used to manage and orchestrate the containers running on the cluster. Some examples of Kubernetes objects include:

• Pods: The smallest and simplest unit in the Kubernetes object model, a pod represents a single instance of a running process in a container, and can contain one or more containers. Pods are used to group together related containers and provide them with shared resources, such as network and storage.
• Replication Controllers: Ensure that a specified number of replicas of a pod are running at any given time. They ensure that a certain number of replicas of a pod are running and also handle self-healing, in case of failure, it starts a new pod.
• Services: Provide a stable endpoint for accessing a set of pods. They abstract the pods behind a stable endpoint and also handle load balancing traffic to the pods.
• Deployments: High-level object to manage replicated applications, it provides declarative updates for Pods and Replication Controllers.
• ConfigMaps and Secrets: used to store configuration data, such as environment variables and command-line arguments, that are needed by the containers in the pods.
• StatefulSets: it ensures that pods with a unique identity are started and stopped in a predictable order, it’s mainly used to handle stateful application such as databases.
• CronJobs: allows you to run Kubernetes Jobs on a time-based schedule.

This is not an exhaustive list of Kubernetes objects and the exact set of objects will depend on the version and configuration of your cluster. Each object has a unique set of characteristics and features that makes it well suited for specific use cases.

It’s important to understand that each object represents a desired state of the system, the Kubernetes control plane will continuously ensure that the current state of the system matches the desired state.

How Kubernetes Works

Kubernetes works by using a cluster of nodes, each of which runs a container runtime (such as Docker) and the Kubernetes components necessary to manage the containers. The cluster is managed by a set of control plane components, including the etcd key-value store, which stores the configuration data for the cluster, and the API server, which exposes a RESTful API that can be used to interact with the cluster.

The overall process of how Kubernetes works can be summarized in the following steps:

1. The user submits a desired state for the application in the form of manifests, usually in YAML or JSON format, that define the resources they want to run, like pods, services and so on.
2. The control plane, which is composed of multiple components such as the API server, the etcd store, and the controller manager and the scheduler, receives and processes the manifests.
3. The controller manager and scheduler take care of the desired state, the former makes sure that the current state of the system matches the desired state by monitoring and reconciling any discrepancies, while the latter assigns pods to the appropriate nodes based on the resource requirements and constraints.
4. The kubelet, which runs on each node, receives instructions from the control plane on how to manage the pods, it ensures that the containers are running and in a healthy state, and if not, it will take appropriate actions to bring them back to a healthy state.
5. The pods, which are the basic unit of the Kubernetes object model, represent a single instance of a running process in a container and can contain one or more containers. Pods are used to group together related containers and provide them with shared resources, such as network and storage.
6. Services, provide a stable endpoint for accessing a set of pods, abstract the pods behind a stable endpoint and also handle load balancing traffic to the pods.

This simplified workflow demonstrates the overall process of how Kubernetes works, there is more to it than just this, and the exact details of how it works will depend on the version and configuration of your cluster. But the key takeaway is that Kubernetes is constantly monitoring and reconciling the desired state with the current state of the system to ensure that the application is running smoothly and efficiently.

Advantages And Disadvantages Of Kubernetes

Kubernetes is a powerful and flexible container orchestration system that offers many advantages for managing and deploying containerized applications. However, like any technology, it also has its own set of disadvantages.

Advantages of Kubernetes:

• Scalability: Kubernetes makes it easy to scale your application up or down based on the demand, it can automatically distribute the load between the different pods and scale the number of replicas up or down.
• High availability: Kubernetes provides built-in support for high availability, ensuring that your application is always available and that there is no downtime during updates or failures.
• Portability: It allows you to run the same application on multiple environments, such as on-premises, public cloud, or hybrid cloud.
• Self-healing: Kubernetes can automatically detect and recover from failures, it can also automatically replaces and reschedules the pods that failed.
• Automation: Kubernetes provides a unified way to manage and orchestrate containers, regardless of the underlying infrastructure, it eliminates the need for manual tasks and reduces the time it takes to deploy and manage applications.
• Large ecosystem: Kubernetes has a large and active community that develops and contributes to various projects and add-ons which can enhance the features of your cluster.

Disadvantages of Kubernetes:

• Complexity: Kubernetes can be complex to set up and configure, it requires a certain level of expertise to get it up and running properly.
• Resource requirements: Kubernetes requires a significant amount of resources to run, such as memory and storage, which can be a disadvantage in environments with limited resources.
• Learning curve: The Kubernetes ecosystem is vast and it may take some time to learn and understand all of its features and capabilities.
• Networking: Kubernetes networking can be complex, different networking solutions can have different capabilities and limitations.
• Cost: Running a Kubernetes cluster may require additional resources and the cost can vary depending on the cloud provider or the on-premises infrastructure.

Keep in mind that these are general advantages and disadvantages, the actual impact will depend on your specific use case and requirements. Kubernetes can be a powerful tool when used correctly and in the right context, it can provide numerous benefits over a traditional application deployment. However, if not used properly it can also be quite a burden.