Kubernetes for JS Developers

Kubernetes is an open-source system for automating deployment, scaling, and management of containerized applications. It ensures that pods (which can be thought of as containers) are always running, handles networking between pods, and allows for easy scaling of applications.

A pod is the smallest deployable unit in Kubernetes. It consists of one or more containers that share storage and network resources. Pods can be managed, scaled, and restarted by Kubernetes.

A deployment in Kubernetes provides declarative updates for pods and replica sets. You describe the desired state in a deployment manifest, and Kubernetes handles the rest, ensuring that the actual state matches the desired state. Deployments make it easier to manage, scale, and update applications.

A service in Kubernetes is an abstract way to expose an application running on a set of pods as a network service. It provides a single DNS name to access a set of pods and can load balance traffic among them.

To expose a Kubernetes application to the outside world, you use an Ingress resource. An Ingress manages external access, typically HTTP, to the services in a cluster. It can provide load balancing, SSL termination, and name-based virtual hosting.

Minikube is a tool that allows you to run a Kubernetes cluster locally. It creates a virtual machine on your local machine and deploys a simple Kubernetes cluster for development and testing purposes. You can interact with this cluster using kubectl commands.

To scale an application in Kubernetes, you use the `kubectl scale` command on a deployment. This command allows you to set the desired number of replicas, and Kubernetes will automatically create or terminate pods to match the desired state.

kubectl is a command-line tool used to interact with a Kubernetes cluster. It allows you to deploy applications, inspect and manage cluster resources, and view logs. Common commands include `kubectl apply` to deploy resources, `kubectl get` to list resources, and `kubectl logs` to view logs from pods.

To create a deployment and service in Kubernetes, you write YAML manifest files that define the desired state of your deployment and service. The deployment file specifies the number of replicas, the container image to use, and other settings. The service file includes information about which pods to expose and the ports to use. You then apply these files using the `kubectl apply` command.

Labels are key-value pairs attached to Kubernetes objects like pods and services. They are used to organize and select subsets of objects. Selectors are used to filter and match these labeled objects. For example, a service uses selectors to identify which pods it should expose based on their labels.