Before we learn Kubernetes, let's learn:
Today's internet user never accept downtime. Therefore developers have to find a method to perform maintenance and update without interrupting their services.
Therefore container, which is isolated environments. It includes everything needed for application to run. It makes it easy for a developer to edit and deploying apps. Moreover, containerization has become a preferred method for packaging, deploying, and update web apps.
Kubernetes is a container management system developed in the Google platform. It helps you to manage a containerized application in various types of Physical, virtual, and cloud environments.
Google Kubernetes is highly flexible container tool to deliver even complex applications, consistently. Applications 'run on clusters of hundreds to thousands of individual servers."
In this beginners Kubernetes tutorial, you will learn:
- Why you need containers?
- What is Kubernetes?
- What task are performed by Kubernetes?
- Why use Kubernetes?
- Features of Kubernetes
- Kubernetes Basics
- Kubernetes Architecture
- Other Key Terminologies
- Kubernetes vs. Docker Swarm
- Disadvantages of Kubernetes
Kubernetes is the Linux kernel which is used for distributed systems. It helps you to be abstract the underlying hardware of the nodes(servers) and offers a consistent interface for applications that consume the shared pool of resources.
Here, are pros/benefits of using Kubernetes.
- Kubernetes can run on-premises bare metal, OpenStack, public clouds Google, Azure, AWS, etc.
- Helps you to avoid vendor lock issues as it can use any vendor-specific APIs or services except where Kubernetes provides an abstraction, e.g., load balancer and storage.
- Containerization using kubernetes allows package software to serve these goals. It will enable applications that need to be released and updated without any downtime.
- Kubernetes allows you to assure those containerized applications run where and when you want and helps you to find resources and tools which you want to work.
Here are the essential features of Kubernetes:
- Automated Scheduling
- Self-Healing Capabilities
- Automated rollouts & rollback
- Horizontal Scaling & Load Balancing
- Offers environment consistency for development, testing, and production
- Infrastructure is loosely coupled to each component can act as a separate unit
- Provides a higher density of resource utilization
- Offers enterprise-ready features
- Application-centric management
- Auto-scalable infrastructure
- You can create predictable infrastructure
Here, are some important Basic of Kubernetes:
Cluster:It is a collection of hosts(servers) that helps you to aggregate their available resources. That includes ram, CPU, ram, disk, and their devices into a usable pool.
Master:The master is a collection of components which make up the control panel of Kubernetes. These components are used for all cluster decisions. It includes both scheduling and responding to cluster events.
Node:It is a single host which is capable of running on a physical or virtual machine. A node should run both kube-proxy, minikube, and kubelet which are considered as a part of the cluster.
Namespace:It is a logical cluster or environment. It is a widely used method which is used for scoping access or dividing a cluster.
The master node is the first and most vital component which is responsible for the management of Kubernetes cluster. It is the entry point for all kind of administrative tasks. There might be more than one master node in the cluster to check for fault tolerance.
The master node has various components like API Server, Controller Manager, Scheduler, and ETCD. Let see all of them.
API Server: The API server acts as an entry point for all the REST commands used for controlling the cluster.
The scheduler schedules the tasks to the slave node. It stores the resource usage information for every slave node. It is responsible for distributing the workload.
It also helps you to track how the working load is used on cluster nodes. It helps you to place the workload on resources which are available and accept the workload.
etcd components store configuration detail and wright values. It communicates with the most component to receive commands and work. It also manages network rules and port forwarding activity.
Worker nodes are another essential component which contains all the required services to manage the networking between the containers, communicate with the master node, which allows you to assign resources to the scheduled containers.
- Kubelet: gets the configuration of a Pod from the API server and ensures that the described containers are up and running.
- Docker Container: Docker container runs on each of the worker nodes, which runs the configured pods
- Kube-proxy: Kube-proxy acts as a load balancer and network proxy to perform service on a single worker node
- Pods: A pod is a combination of single or multiple containers that logically run together on nodes
A replication controller is an object which defines a pod template. It also controls parameters to scale identical replicas of Pod horizontally by increasing or decreasing the number of running copies.
Replication sets are an interaction on the replication controller design with flexibility in how the controller recognizes the pods it is meant to manage. It replaces replication controllers because of their higher replicate selection capability.
Deployment is a common workload which can be directly created and manage. Deployment use replication set as a building block which adds the feature of life cycle management.
It is a specialized pod control which offers ordering and uniqueness. It is mainly used to have fine-grained control, which you have a particular need regarding deployment order, stable networking, and persistent data.
Daemon sets are another specialized form of pod controller that runs a copy of a pod on every node in the cluster. This type of pod controller is an effective method for deploying pods that allows you to perform maintenance and offers services for the nodes themselves.
|Load balancing||Does auto load balancing||Manually configure your load balancing settings|
|Storage volume sharing||Shares storage volumes with any other container||Shares storage volumes between multiple containers inside the same Pod|
|Use of logining and monitoring tool||Use 3rd party tool like ELK||Provide an in-built tool for logging and monitoring.|
|Installation||Easy & fast||Complicated & time-consuming|
|GUI||GUI not available||GUI is available|
|Scalability||Scaling up is faster than K8S, but cluster strength not as robust||Scaling up is slow compared to Swarm, but guarantees stronger cluster state Load balancing requires manual service configuration|
|Load Balancing||Provides a built-in load balancing technique||Process scheduling to maintain services while updating|
|Updates & Rollbacks Data Volumes Logging & Monitoring||Progressive updates and service health monitoring.||Only shared with containers in same Pod Inbuilt logging & monitoring tools.|
- Kubenetes dashboard not as useful as it should be
- Kubernetes is a little bit complicated and unnecessary in environments where all development is done locally.
- Security is not very effective.
- Container helps an organization to perform maintenance and update without interrupting services
- Kubernetes is an example of a container management system developed in the Google platform.
- The biggest advantage of using Kubernetes is that it can run on-premises OpenStack, public clouds Google, Azure, AWS, etc.
- Kubernetes offers automated Scheduling and Self-Healing Capabilities.
- Cluster, master, node, and namespace are important basic of kubernetes
- Master node and work node are important components of Kubernetes architecture.
- Replication Controllers, Replication sets, Deployments, Stateful Sets, Daemon Sets are other important terms used in Kubernetes.
- Docker swarm does not allow auto-scaling while Kubernetes allows auto-scaling.
- The biggest drawback of Kubenetes is that it's dashboard not very useful and effective