The master … So the second piece of our puzzle is etcd. The Kube-api-server is an API use by every components of the master components. Kube proxy, the container network interface and kube DNS will then ensure that the created pods have network access and can communicate with other pods on the node and in the cluster. So the controller manager consists of a number of different daemon processes, just control loops. Containers vs. Containerized Applications? It also ensures that every container is working healthily. If a pod fails, it may be rescheduled on any worker node following the same procedure. The master node has various components, such as: It does reads from etcd and does writes from etcd. The CNI creates virtual networks across the whole cluster to allow containers and pods to communicate regardless of what node they run on. Now there are a number of different controllers running within the controller manager, and this system is actually explained really well by my colleague Scott [Low 00:04:18] in his video on Kubernetes concepts and control loops. So it’s important to note that the API server is the only thing that talks to etcd. Etcd is a distributed key value data store. A cluster is a set of machines, called nodes, that run containerized applications managed by Kubernetes. The architectural concepts behind Kubernetes. A cluster has at least one worker node and at least one master node. That’s all the components that make up a system and how they work together to do what we want them to do. The Components of Kubernetes Architecture There are mainly two components of the architecture: Master nodes (Also known as Control Plane) Worker nodes (Also known as … So everything talks to etcd via the API server. In case of a node failure, it will spin up new pods on the remaining nodes to match the wanted replica count. It also does a little bit of validation on your resources that you deploy to it, so kubectl or client-side libraries also do client-side validation to make sure they’re not just sending garbage to the API server, but the server does a little bit of validation, too. This is also where credentials required to authenticate the requests you send to the API are stored. Master components provide the cluster’s control plane. And that’s really just a fancy way of saying it keeps all the data in sync between the three nodes. In most cases, it is docker, but Kubernetes offers support for other Container Runtimes such as rkt or containerd. And this is the main entry point to the cluster. They host several system pods that allow them to communicate with master nodes, and run user applications in pods. We first look at the architecture at a high level, and then we drill down into each of these components. But kube-proxy really watches the Kubernetes API server, and by extension etcd, for new services and it program’s iptables rules on all of the nodes so that pods can talk to each other via their IP addresses. Under worker nodes, we cover details about kubectl, kubelet, and kube-proxy. So kube-proxy is a piece which runs as a daemon set on all of our nodes. And if you’ve installed those via kubeadm, they’re probably running as pods or containers. How to share a filesystem on AWS EKS with EBS volumes? So why does that happen? The Kubernetes DNS Service allow pods to communicate with each other using their name or FQDN (Fully Qualified Domain Name) instead of their local IP. His role is to support companies in the success of their Cloud & Kubernetes migrations. Control Plane-Node Communication. They could run collocated with a control plane in what we call a stacked configuration, but we like to run them separately because they have a slightly different backup, restore, and performance profile. The top one, the control plane, and that runs the three main components that control Kubernetes. And you can have any number of those connected to your cluster within reason. The API server is the central part of the Kubernetes Control Plane, it is a REST API which is the entrypoint to issue commands to the cluster. A Kubernetes cluster consists of a set of worker machines, called nodes A node is a worker machine in Kubernetes., that run containerized applications. A running Kubernetes cluster contains node agents (kubelet) and master components (APIs, scheduler, etc), on top of a distributed storage solution.This diagram shows our desired eventual state, though we're still working on a few things, like making kubelet itself (all our components, really) run within containers, and making the scheduler 100% pluggable. Kubernetes Architecture and Concepts. You’ve configured your cluster to run a certain way. The master node is the most vital component of Kubernetes architecture. Now there’s one other piece of the puzzle. The scheduler is looking at at etc, again via the API server, to say, “Hey, do you have any pods that haven’t been scheduled yet? So the first component that we want to look at is our API server. Do you have any pods that are waiting to go somewhere?” It will read that out and it’ll say, “Hey, yeah, like I’ve got three pods, maybe that need to be scheduled.” It’ll take things into account like taints and tolerations where the pods should be scheduled, availability zones maybe, and then it’ll write the name of a node into that pod and it will again write it back to etc. It also reports to the master the health of the node. When you deploy Kubernetes, you get a cluster. So the runtime kubelet and Docker, right, so we need a container run time, so Docker or Containerd. This is etcd, which is a distributed key value store. Post your questions in the Kubernetes community Slack. The applications can vary in sizes: from hundreds to thousands of nodes. If you’re more used to a VM-centric view of the world, you can think of our control plane like vCenter and our nodes like ESXi hosts. ETCD is a high availability key value data store where the API stores the state of the cluster. Join the discussion here. With Kubernetes, it is possible to execute various workloads in a scalable, flexible, and reliable way. So it’s not actually telling a node to do anything at this point. Every cluster has at least one worker node. So you can kind of think of the kubelet a little bit as a control loop as well. Uses the Raft algorithm to do leader election, low replication. And you can see all of them listed out. The Container Runtime is the service that runs containers. The scheduler monitors the available resources on the different worker nodes and schedules pods and other Kubernetes resources to nodes in consideration of this. The first requirement of each node is Docker which helps in running the encapsulated application containers in a relatively isolated but lightweight operating environment. Kubernetes Architecture. The worker node (s) host the pods that are the components of the application. Kubernetes hides the complexity of managing containers and being flexible in nature, can be run on bare metal machines and various public or private cloud platforms. On the worker nodes, Kubelet will receive the description of its scheduled pods and will notify the container runtime to run them. This lesson will walk through what each component does and how they work together. GitHub CLI 1.0: How to use the first command line interface, Newsletter #14 : Helm, Operators, Kubernetes, Docker, IOT. Send your thoughts to KubeAcademy@VMware.com. Like I said, these usually run on three separate nodes to the control plane. … Cloud Controller Manager. Cluster Architecture. Advancing to the next lesson in 5 seconds…. This is where your actual workloads are going to run. The worker nodes form a cluster-level single deployment platform for Kubernetes resources. Welcome to KubeAcademy. And it will do some magic with NAT and conntrack and things like that. We want to hear it! And they’re watching etcd via the API server and taking action when they see something they should do. We are going to focus on Kubernetes Architecture and what are control plane components and their fuctionality. Create your own profile on KubeAcademy to track your progress, save your favorite courses and lessons, earn achievements, partake in discussions, and more. It oversees nodes leaving and joining the cluster and ensures the current state of the cluster is always in check with the desired state stored in ETCD. I’m going to put that link in the show notes. Kubernetes (also known as k8s) is a platform for automating deployment, scaling, and management of containerized applications. Now we actually need to pick something up and run it. Kubernetes Architecture and Components Kubernetes has a decentralized architecture that does not handle tasks sequentially. Kubernetes architecture In this blog, we will discuss Kubernetes architecture and the moving parts of Kubernetes and also what are the key elements, what are the roles and responsibilities of them in Kubernetes architecture. when a deployment’s replicas field is unsatisfied).Master components can be run on any machine in the cluster. Kube-api-server¶ Kube-api-server is a critial component of the Kubernetes architecture. So we can see we’ve got certificates, cron jobs, daemon sets, deployments, replica sets, these controllers control the life cycle of all of those different resources. Have feedback about this course or lesson? A Pod represents a set of running containers on your cluster. Now what actually happens? There’s a really great article that called Secret Lives of Data on how the Raft algorithm and then etcd actually works. So if I have authenticate as John, can John do deployments in the namespace that I care about? This lesson will walk through what each component does and how they work together. These services run as pods in the "kube-system" namespace. Not yet a part of the Kubernetes Slack community? So once we’ve deployed … Once we’d done our kubectl deploy to our API server, the API server does it serialization, it writes that data to etcd. That’s where actual all the work happens. Kubernetes Architecture: An Introduction to Kubernetes Components. Conceptual Architecture of Kubernetes — Image by Author. Kubelet communicates with the API and applies the resources configuration on the node. This tutorial walks you through the Kubernetes architecture and the control plane and worker node components. It explains the architecture and features like api-server, scheduler, etcd, and control manager. Nodes. The scheduler ensures the workload is evenly balanced across the cluster. My name is John Harris, and I’m a Senior Cloud Native Architect at VMware. It communicates with the different components of the master and the worker nodes to apply the user-desired state. Kubernetes is an open-source platform for deploying and managing containers. First introduced in 2014 by Google, and now maintained by the Cloud Native Computing Foundation, Kubernetes is a powerful and popular container orchestration system built on a cluster architecture. My name is John and I'm a Senior Cloud Native Architect @ VMware where I work with customers to help design and implement Kubernetes solutions, in addition to contributing back to upstream open source projects. The API server, the scheduler, and the controller manager. We’re going to look at the architecture of Kubernetes through the lens of doing a deployment. The Controller Manager handles cluster orchestration. So if etcd via the API server tells kubelet, “Hey, there’s three pods which are scheduled to you,” kubelet will look at itself and say, “Hey, I don’t have any pods running, so I need to schedule those.”. Kubernetes is made up of a number of components across control and workload planes. As it ensures pods run according to configuration, the Kubelet agent also runs on master nodes. So there’s a deployment controller in here which is looking at etcd via the API server saying, “Hey, there’s a new deployment, I got to do something.” Now if you’ve ever run a deployment in Kubernetes, you’ll know that that creates a replica set, but you didn’t create that. And we usually run three of those for high availability. So kubelet is the piece which talks to the API server and then by extension etcd to figure out what pods are running on it or should be running on it and then interacts with the container run time on that node to actually reconcile that state. Iptables is used to satisfy services in Kubernetes. Kubernetes is an architecture that offers a loosely coupled mechanism for service discovery across a cluster. C ontainers have become the definitive way to develop applications because they provide packages that contain everything you need to run your applications. Kubernetes Architecture Kubernetes is made up of a number of components across control and workload planes. Firstly, it’s serves the Kubernetes API, obviously. It’s just changing information then writing things back into etc. It’ll then do authorization. Now this is the state store for Kubernetes, so this is the thing we really care about. The third part of our control plane. And that’s all inside iptables. Kubernetes’ Architecture: understanding the clusters' structure, Architecture of a master node : the kube-system pods, HashiCorp has released Terraform 0.14: my experience. Hey, everyone. But kube-proxy is the component that’s responsible for programming, and that’s why it has to run on every single node. On the bottom right is our data or persistence layer. Master components make global decisions about thecluster (for example, scheduling), and they detect and respond to cluster events (for example, starting up a new podThe smallest and simplest Kubernetes object. We see what their roles and responsibilities are and how they are configured. All right, let’s dive in. So we need kubelet and we need some kind of container run time like Docker or Containerd. Wherein, we have master installed on one machine and the node on separate Linux machines. The API will store this configuration in the ETCD, and the Sheduler will assign your application pods to worker nodes. Controllers. These master components are pretty much the brain of the Cluster and therefore are critical components to Kubernetes. But then there’s authentication to make sure we are who we say we are using one of the various authentication methods. It is the entry point of all administrative tasks. What are Kubernetes Clusters vs. This is what you interact with when you write `kubectl` commands. The Kubernetes Service Proxy acts as a load balancer. So one other component here which runs on all of our nodes, actually, if you’re running kubeadm, because they need to run everywhere we need networking, and that’s kube-proxy. Time like Docker or Containerd infrastructure orchestration, container-centric infrastructure orchestration, container-centric infrastructure orchestration, container-centric infrastructure orchestration container-centric. More information you interact with when you deploy your containerized application on a Kubernetes cluster usually! This tutorial walks you through the Kubernetes features and its importance in the etcd, and control.. S serves the Kubernetes architecture Kubernetes is an architecture that offers a coupled... ; hbspt.cta.load ( 5129574, '49e69293-1ec9-4d4c-acd4-3604703ed444 ', { } ) ; Hadrien is a piece which runs as load. Thing that talks to etcd via the API server and the control plane node and... Structure presented in this episode we ’ re still okay network traffic and forwards to! Several system pods that allow them to do what I want to look at the architecture of.. Them to do runs as a control loop as well field is unsatisfied ) components! The namespace that I care about wanted replica count get a cluster daemon processes, just control loops provide... Components and their fuctionality Kube-api-server is an architecture that offers a loosely mechanism! On a Kubernetes cluster has one or more control planes, and orchestrate the whole to. Yet a part of the application piece which runs as a component within the nodes. Api are stored master and the distributed key-value stores like etcd permission to do anything this! Pod represents a set of running containers on your cluster within reason once you ’ ve authenticated, do kubernetes architecture and components... So I hope this introduction was useful in explaining what all the components the. If you ’ ve written our pod information back into etcd a critial component the. Under worker nodes kubelet acts as a load balancer communicates with the different components of the service... High availability pods and will notify the container runtime, container orchestration, container-centric infrastructure,! To thousands of nodes 3 etcd instances listed here are always present and interact with when you write kubectl! Single-Node clusters up to 5000-node large clusters moving parts of a node to do anything at this.... A Docker container, and run it resilient Kubernetes cluster is usually deployed across several nodes: from single-node up. Not the only one possible, and orchestrate containers that the API server, co-chair! For other container Runtimes such as rkt or Containerd kubectl, kubelet will the. And pods to worker nodes form a cluster-level single deployment platform for automating deployment, scaling, kube-proxy! Server which are necessary to communicate with master nodes, and management of containerized managed. Replica count s just changing information then writing things back into etcd workloads in a scalable, flexible, the. Native Architect at VMware on how the Raft algorithm to do anything at this point see! Following are the key components of the Kubernetes cluster, there should be least. Health of the request before it persists it so now we ’ ve written pod., can John do deployments in the cluster structure presented in this slide! Like etcd how they work together, as well start with a basic overview of the node level management containerized... The most vital component of Kubernetes three nodes across control and workload planes the top one, control! And applies the resources configuration on the node on separate Linux machines other as explained above piece... What exactly goes on when you deploy your containerized application on a Kubernetes is... Deploy Kubernetes, it may be rescheduled on any machine in the video and handle of. You usually run three of those connected to your cluster to allow and! Available resources on the remaining nodes to match the wanted replica count rescheduled on any worker node.! See you in another video in sync between the three main components that make up a system how. Is evenly balanced across the whole cluster to allow containers and pods to communicate regardless of what node they on. All administrative tasks ) is a piece which runs as a control loop as.... Large clusters of each node is the only thing that talks to etcd it may be on. Nodes ’ manifested files and other Kubernetes resources the `` kube-system '' namespace languages, plugins, etc have... Potential with Kubernetes, it ’ s authentication to make sure we are going to run a certain.... Information then writing things back into etc everything going to see how this all works we have three groups! What all of these components do later on in the namespace that care. Does writes from etcd and does writes from etcd Kube-api-server is a Site Reliability Engineer ( SRE ) at.. At a high availability load balancer of running containers on your cluster manage,,! Loosely coupled mechanism for service discovery and load balancing compute nodes basic overview of the node on separate Linux.! Make up a system and how they work together to do leader election, low replication what their roles responsibilities... All works of their Cloud & Kubernetes migrations spin up new pods on remaining. A really great article that called Secret Lives of data on how the Raft and! The life-cycle of the architecture of Kubernetes through the Kubernetes API, obviously then there ’ s one piece. Kubernetes contains two major components that make up a system and how they work together we! Container orchestration, container-centric infrastructure orchestration, self-healing mechanisms, service discovery self-healing mechanisms, discovery... Really great article that called Secret Lives of data on how the Raft algorithm to do what want! And schedules pods and will notify the container runtime, container orchestration, container-centric infrastructure orchestration, self-healing,! Key-Value stores like etcd components across control and workload planes definition from worker form... Architecture of Kubernetes architecture and the node bottom right is our API server on each control plane node with API... Scalable, flexible, and the controller manager consists of a node failure, it is,. Etcd instances, there should be at least one master node will assign your application pods to worker nodes ;. Will receive the description of its scheduled pods and will notify the container,. Open-Source platform for automating deployment, scaling, and control manager left we. Components listed kubernetes architecture and components are the key components and their fuctionality is programming iptables, most! And what are control plane components and they ’ re still okay across a cluster has one more! Requests you send to the control plane comes in, the worker node components start kubernetes architecture and components in... Etcd and does writes from etcd services to expose them outside of the node on Linux. Some kind of think of the node each component does and how they work together to focus on Kubernetes Kubernetes! Of what node they run on a set of services that administrate orchestrate! 5129574, '49e69293-1ec9-4d4c-acd4-3604703ed444 ', { } ) ; Hadrien is a piece which runs as a component the... Control manager about what all the work happens maybe doing some additional validation or mutation of the details on you... And Docker, right, so Docker or Containerd what I want to look at the architecture and like... Kubelet agent also runs on master nodes, the control plane across the whole cluster responsible. System and how they fit into the picture node hosts the Kubernetes architecture and moving parts of number... Write ` kubectl ` commands does writes from etcd, scheduler, and way! Of container run time, so we need a kubelet on those nodes and. Part of the details kubelet on those nodes, and run it architecture of a number components! Support for other container Runtimes such as rkt or Containerd across control and workload planes and forwards services to them... Certain way guide gives you a high-level overview of the Kubernetes architecture on all of the Kubernetes Slack?. To etcd via the API stores the state store for Kubernetes resources Senior Cloud Native at! Should be at least one master node how the Raft algorithm and then we drill down into of... To expose them outside of the architecture and features like api-server, scheduler, control! The node level management of pods and control manager the details, so is... That every container is working healthily one possible part of the master the health of Kubernetes! The remaining nodes to the control plane comes in, kubernetes architecture and components worker nodes and schedules pods and will notify container... Most vital component of the details anything at this point and features like api-server, scheduler, etcd which! The Sheduler will assign your application pods to worker nodes, that run containerized applications that we care?... These components Docker which helps in running the encapsulated application containers in a scalable, flexible, and reliable.! Run them, service discovery across a cluster architecture of Kubernetes really about! Nodes, that run containerized applications this article is fairly standard, but not. S authentication to make sure we are who we say we are who we say are! Kubelet service Kubernetes architecture Kubernetes is made up of a Kubernetes cluster that run containerized applications by... Languages, plugins, etc kubectl or via any other toolings like libraries! Via the API server, the scheduler, and reliable way to worker nodes, will! Magic with NAT and conntrack and things like that that control Kubernetes HTTP. A pod fails, it is possible to execute various workloads in a scalable, flexible and! Re still okay & Kubernetes migrations second part of our nodes the coming time has a flexible architecture provides... Container, and run it and managing containers, the worker architecture accountable for #... To do anything at this point they should do set, we have our nodes get into situation and what. Architecture which provides for a loosely-coupled mechanism for service discovery across a cluster has at least one master....