Kubernetes Explained in 6 Minutes | k8s Architecture

Summary

Kubernetes, an open-source container orchestration platform, automates the deployment, scaling, and management of containerized applications. Originating from Google's Borg, it facilitates a scalable and highly available system with self-healing and automatic rollbacks. Despite its complexity and high resource requirements, Kubernetes offers portability across different infrastructures. Managed Kubernetes services like Amazon EKS, GKE, and AKS provide an accessible entry point for organizations, balancing the need for orchestration with the overhead of managing the system.

Takeaways

• 📚 Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications.
• 🔍 It originated from Google's internal system, Borg, and was open-sourced in 2014, which is why it's called Kubernetes.
• 🤓 The abbreviation 'k8s' comes from the 8 letters between the 'k' and 's' in Kubernetes, similar to 'i18n' for internationalization.
• 🌐 A Kubernetes cluster consists of nodes that run containerized applications, with a control plane managing the cluster's state.
• 🛠️ The control plane includes core components like the API server, etcd, scheduler, and controller manager, each with specific responsibilities.
• 📦 Pods are the smallest deployable units in Kubernetes, hosting one or more containers and providing shared storage and networking.
• 🔄 The scheduler in Kubernetes is responsible for efficiently placing pods onto worker nodes based on resource requirements.
• 🛑 The controller manager runs controllers that maintain the desired state of the cluster, including replication and deployment controllers.
• 🔧 Worker nodes contain components like kubelet, container runtime, and kube-proxy, which manage pod execution and network traffic.
• ⚖️ Kubernetes offers scalability, high availability, self-healing, and portability, making it adaptable to various infrastructures.
• 💡 The complexity and cost of setting up and managing Kubernetes can be mitigated by using managed Kubernetes services provided by cloud providers.
• ❗ For smaller organizations, the principle of YAGNI (You ain’t gonna need it) may apply, suggesting that Kubernetes might be overkill for their needs.

Q & A

What is Kubernetes?

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications.

Why is Kubernetes abbreviated as 'k8s'?

The abbreviation 'k8s' comes from the 8 letters between the 'k' and the 's' in the word 'Kubernetes', following a common practice in tech to abbreviate long words.

What is the origin of Kubernetes?

Kubernetes originated from Google's internal container orchestration system called Borg, which was open-sourced in 2014.

What are the two core components of a Kubernetes cluster?

The two core components of a Kubernetes cluster are the control plane, responsible for managing the state of the cluster, and the worker nodes, which run the containerized application workloads.

What is the role of the control plane in a Kubernetes cluster?

The control plane is responsible for managing the state of the cluster, including the API server, etcd, scheduler, and controller manager, which handle various aspects of cluster management.

What are Pods in Kubernetes?

Pods are the smallest deployable units in Kubernetes, hosting one or more containers and providing shared storage and networking for those containers.

What is the function of the scheduler in the control plane?

The scheduler is responsible for scheduling pods onto the worker nodes in the cluster, making placement decisions based on the resources required by the pods and the available resources on the worker nodes.

What are the main components that run on the worker nodes in Kubernetes?

The main components running on the worker nodes include kubelet, container runtime, and kube-proxy, which handle communication with the control plane, container operations, and network routing, respectively.

Why is Kubernetes considered scalable and highly available?

Kubernetes is scalable and highly available due to features like self-healing, automatic rollbacks, and horizontal scaling, allowing applications to scale up and down quickly in response to demand changes.

What are the downsides of using Kubernetes?

The downsides of using Kubernetes include its complexity in setup and operation, which requires a high level of expertise and resources, and the cost associated with running the system to support its features.

What is a managed Kubernetes service and how does it benefit organizations?

A managed Kubernetes service is provided by cloud providers like Amazon EKS, GKE on Google Cloud, and AKS on Azure. It allows organizations to run Kubernetes applications without managing the underlying infrastructure, handling tasks that require deep expertise.

Outlines

00:00

🤖 Introduction to Kubernetes

Kubernetes is an open-source platform for automating deployment, scaling, and management of containerized applications. Originating from Google's Borg, Kubernetes was open-sourced in 2014. The name 'k8s' is an abbreviation representing the 8 letters between 'k' and 's'. A Kubernetes cluster comprises nodes, with a control plane managing the cluster's state and worker nodes running the applications in Pods, which are the smallest deployable units. The control plane includes the API server, etcd, scheduler, and controller manager, each with specific responsibilities for cluster management and state maintenance. Worker nodes feature components like kubelet, container runtime, and kube-proxy to ensure smooth operation and traffic management.

05:01

🚀 Advantages and Considerations of Using Kubernetes

Kubernetes offers scalability, high availability, self-healing, automatic rollbacks, and horizontal scaling, allowing for quick adaptation to demand changes. It also provides portability across different environments, ensuring consistent application deployment. However, the platform's complexity requires significant expertise and resources, making it potentially overwhelming for smaller organizations. The cost of running Kubernetes can be high, but managed Kubernetes services from cloud providers like Amazon EKS, Google's GKE, and Azure's AKS offer a balance by handling infrastructure and maintenance. For small organizations, the principle of YAGNI (You Ain't Gonna Need It) is recommended, suggesting that Kubernetes might be more than necessary. The script also encourages further learning about system design through books and newsletters.

Keywords

💡Kubernetes

Kubernetes is an open-source container orchestration platform designed to automate the deployment, scaling, and management of containerized applications. It is central to the video's theme as it explains the origin, functionality, and components of Kubernetes. The script mentions Kubernetes' roots in Google's Borg system and its evolution into an open-source project, highlighting its significance in modern application management.

💡k8s

k8s is an abbreviation for Kubernetes, derived from the 8 letters between the 'k' and 's' in the full name. The video script uses this abbreviation to illustrate a common practice in tech for shortening lengthy terms, such as 'i18n' for internationalization. It serves as a cultural reference point within the tech community and is relevant to the video's narrative on Kubernetes.

💡Container Orchestration

Container orchestration refers to the automation of container management tasks such as deployment, scaling, and load balancing. In the video, Kubernetes is described as a container orchestration platform, emphasizing its role in simplifying the complex process of managing containerized applications across multiple hosts.

💡Control Plane

The control plane in Kubernetes is responsible for managing the state of the cluster. It includes core components like the API server, etcd, scheduler, and controller manager. The script explains that the control plane is crucial for the operation of a Kubernetes cluster, as it handles the cluster's persistent state and facilitates communication with other components.

💡Worker Nodes

Worker nodes in a Kubernetes cluster are the machines that run the containerized application workloads. The script describes worker nodes as an integral part of the cluster, alongside the control plane, and details the components that run on these nodes, such as kubelet and kube-proxy, which are essential for maintaining the desired state of pods and routing traffic.

💡Pods

Pods are the smallest deployable units in Kubernetes, hosting one or more containers and providing shared storage and networking for them. The video script uses the concept of pods to explain the basic building blocks of Kubernetes applications and how they are created and managed by the control plane.

💡API Server

The API server in Kubernetes is the primary interface between the control plane and the rest of the cluster. It exposes a RESTful API for clients to interact with the control plane and manage the cluster. The script highlights the API server's role in facilitating communication and request submission within the Kubernetes ecosystem.

💡etcd

etcd is a distributed key-value store used in Kubernetes to store the cluster's persistent state. The script explains that etcd is accessed by the API server and other control plane components to store and retrieve information about the cluster, emphasizing its importance in maintaining cluster state and data consistency.

💡Scheduler

The scheduler in Kubernetes is responsible for making placement decisions regarding where to run pods within the cluster. The script describes how the scheduler uses resource requirements and availability to schedule pods onto worker nodes, illustrating its critical role in optimizing resource utilization and application performance.

💡Kubelet

Kubelet is a daemon that runs on each worker node in a Kubernetes cluster, responsible for communicating with the control plane. The script explains that kubelet receives instructions about which pods to run and ensures the maintenance of the desired state of pods, highlighting its function in the direct management of containerized applications.

💡Kube-proxy

Kube-proxy is a network proxy that runs on each worker node in a Kubernetes cluster, responsible for routing traffic to the correct pods and providing load balancing. The script uses kube-proxy as an example of how Kubernetes ensures efficient traffic distribution and resource management within the cluster.

Highlights

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications.

Kubernetes originated from Google's internal container orchestration system, Borg, which managed the deployment of thousands of applications within Google.

The name 'Kubernetes' is abbreviated as 'k8s', with the '8' representing the 8 letters between the 'k' and 's'.

A Kubernetes cluster consists of machines called nodes that run containerized applications.

The control plane in a Kubernetes cluster manages the state of the cluster and usually runs across multiple nodes and data center zones in production.

Worker nodes in a Kubernetes cluster run the containerized application workloads.

Pods are the smallest deployable units in Kubernetes, hosting one or more containers with shared storage and networking.

The control plane's core components include the API server, etcd, scheduler, and controller manager.

The API server serves as the primary interface between the control plane and the rest of the cluster, exposing a RESTful API for cluster management.

Etcd is a distributed key-value store used for storing the cluster's persistent state.

The scheduler in Kubernetes is responsible for making placement decisions for pods onto worker nodes based on resource requirements.

The controller manager runs controllers that manage the state of the cluster, including replication and deployment controllers.

Kubelet is a daemon on worker nodes that communicates with the control plane and manages the desired state of pods.

The container runtime on worker nodes is responsible for running containers, pulling images from a registry, and managing container resources.

Kube-proxy is a network proxy that routes traffic to the correct pods and provides load balancing.

Kubernetes offers scalability, high availability, self-healing, automatic rollbacks, and horizontal scaling for applications.

Kubernetes is portable and provides a consistent way to package, deploy, and manage applications across different environments.

The main drawbacks of Kubernetes include its complexity in setup and operation, as well as the high upfront cost for organizations new to container orchestration.

Managed Kubernetes services provided by cloud providers like Amazon EKS, GKE, and AKS can help organizations run Kubernetes applications without managing the underlying infrastructure.

For small organizations, the YAGNI principle (You ain’t gonna need it) may apply when considering the adoption of Kubernetes.

Transcripts

What is Kubernetes?

Why is it called k8s?

What makes it so popular?

Let’s take a look.

Kubernetes is an open-source  container orchestration platform.

It automates the deployment, scaling, and  management of containerized applications.

Kubernetes can be traced back to Google's  internal container orchestration system,  

Borg, which managed the deployment of  thousands of applications within Google.

In 2014, Google open-sourced a version of Borg.

That is Kubernetes.

Why is it called k8s?

This is a somewhat nerdy way  of abbreviating long words.

The number 8 in k8s refers to the 8  letters between the first letter “k”  

and the last letter “s” in the word Kubernetes.

Other examples are i18n for  internationalization, and l10n for localization.

A Kubernetes cluster is a set of machines,  

called nodes, that are used to  run containerized applications.

There are two core pieces in a Kubernetes cluster.

The first is the control plane.

It is responsible for managing  the state of the cluster.

In production environments,  the control plane usually  

runs on multiple nodes that span  across several data center zones.

The second is a set of worker nodes.

These nodes run the containerized  application workloads.

The containerized applications run in a Pod.

Pods are the smallest  deployable units in Kubernetes.

A pod hosts one or more containers  

and provides shared storage and  networking for those containers.

Pods are created and managed by  the Kubernetes control plane.

They are the basic building  blocks of Kubernetes applications.

Now let’s dive a bit deeper  into the control plane.

It consists of a number of core components.

They are the API server, etcd,  scheduler, and the controller manager.

The API server is the primary interface between  the control plane and the rest of the cluster.

It exposes a RESTful API that allows  clients to interact with the control  

plane and submit requests to manage the cluster.

etcd is a distributed key-value store.

It stores the cluster's persistent state.

It is used by the API server and  other components of the control  

plane to store and retrieve  information about the cluster.

The scheduler is responsible for scheduling  pods onto the worker nodes in the cluster.

It uses information about the resources  required by the pods and the available  

resources on the worker nodes  to make placement decisions.

The controller manager is responsible for running  controllers that manage the state of the cluster.

Some examples include the replication controller,  

which ensures that the desired number  of replicas of a pod are running,  

and the deployment controller, which manages  the rolling update and rollback of deployments.

Next, let’s dive deeper into the worker nodes.

The core components of Kubernetes that  run on the worker nodes include kubelet,  

container runtime, and kube proxy.

The kubelet is a daemon that  runs on each worker node.

It is responsible for communicating  with the control plane.

It receives instructions from the control  plane about which pods to run on the node,  

and ensures that the desired  state of the pods is maintained.

The container runtime runs the  containers on the worker nodes.

It is responsible for pulling the  container images from a registry,  

starting and stopping the containers,  and managing the containers' resources.

The kube-proxy is a network proxy  that runs on each worker node.

It is responsible for routing  traffic to the correct pods.

It also provides load balancing  for the pods and ensures that  

traffic is distributed evenly across the pods.

So when should we use Kubernetes?

As with many things in software  engineering, this is all about tradeoffs.

Let’s look at the upsides first.

Kubernetes is scalable and highly available.

It provides features like self-healing,  automatic rollbacks, and horizontal scaling.

It makes it easy to scale our  applications up and down as needed,  

allowing us to respond to  changes in demand quickly.

Kubernetes is portable.

It helps us deploy and manage  applications in a consistent  

and reliable way regardless of  the underlying infrastructure.

It runs on-premise, in a public  cloud, or in a hybrid environment.

It provides a uniform way to package,  deploy, and manage applications.

Now how about the downsides?

The number one drawback is complexity.

Kubernetes is complex to set up and operate.

The upfront cost is high, especially for  organizations new to container orchestration.

It requires a high level of  expertise and resources to set  

up and manage a production Kubernetes environment.

The second drawback is cost.

Kubernetes requires a certain minimum level of  

resources to run in order to support  all the features we mentioned above.

It is likely an overkill for  many smaller organizations.

One popular option that strikes a  reasonable balance is to offload  

the management of the control plane  to a managed Kubernetes service.

Managed Kubernetes services are  provided by cloud providers.

Some popular ones are Amazon EKS, GKE  on Google Cloud, and AKS on Azure.

These services allow organizations  to run the Kubernetes applications  

without having to worry about  the underlying infrastructure.

They take care of tasks that require deep  expertise, like setting up and configuring  

the control plane, scaling the cluster, and  providing ongoing maintenance and support.

This is a reasonable option for a mid-size  organization to test out Kubernetes.

For a small organization, YAGNI - You ain’t  gonna need it - is our recommendation.

If you would like to learn more about system  design, check out our books and weekly newsletter.

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