Swetha – Kubernetes Architecture

What are the 10 features of kubernetes ?

1. container orchestrator
2. Workload placement
3. Maintains desired state
4. Self-healing
5. Automated rollbacks
6. Auto scaling
7. Load balancing
8. Speed of deployment
9. Ability to absorb change quickly
10. Hide complexity in the cluster

How Kubernetes works ?

Kubernetes are comprised of master and multiple nodes where Master is In-charge of cluster which manages nodes and nodes manages one or multiple pods and pod manages one or multiple containers.

What are the components of Master ?

1. Kube-API server – front end thru which any communication is passed and consumes JSON via manifest files.
2. Kube-Cluster store – requests gets stored in cluster store in key value format powered by etcd.
3. Kube-Controller manager – controller of controllers which watches for changes and helps in maintaining desired state.
4. Kube-Scheduler – watches API server for new pods, assigns work to nodes and interacts with kubelet in node.

What are the components of Worker ?

1. Kubelet – main kubernetes agent which registers node with cluster and instantiates pods, exposes endpoint on: 10255.
2. Container Engine (Docker) – does container management: pulling images and running containers.
3. Kube –proxy – manages kubernetes networking (pod IP addresses), all containers in a pod share a single IP.

What are the components of Workstation ?

Kubectl – CLI to interact with APIserver

What is POD ?

A pod is the smallest execution unit that you can create and manage in Kubernetes. A Pod  is a group of one or more containers, with shared storage and network resources, and a specification for how to run the containers.

• A pod encapsulates one or more applications.
• When a pod is created it is assigned its own unique IP address.
• Pods have a single IP address that is applied to every container within the pod.
• Containers in a pod share the same resources such as memory and storage (All containers in pod share the pod environment).
• If there are multiple containers within the pod, they can communicate between each other simply by using localhost. Communications outside of the pod is achieved by exposing a port.
• If a pod (or the node it executes on) fails, Kubernetes can automatically create a new replica of that pod to continue operations.
• Communications between pods in a cluster takes advantage of the fact that Kubernetes assigns a cluster-private IP address to every pod in a cluster, eliminating the need to either explicitly create links between pods or to map container ports to host ports.
• Pods utilize an agent on each node called a kubelet to communicate with the Kubernetes API and the rest of the cluster.
• As the load on a pod increases, Kubernetes can automatically replicate the pod to achieve desired scalability.
• multi-container pods ease deployment configuration compared to setting up shared resources between containers on your own.