So if you lose one, you’re still okay. Not yet a part of the Kubernetes Slack community? This is where your actual workloads are going to run. Questions about this lesson are best suited for the #kubernetes-users channel. As it ensures pods run according to configuration, the Kubelet agent also runs on master nodes. when a deployment’s replicas field is unsatisfied).Master components can be run on any machine in the cluster. Janet Kuo, the co-chair of KubeCon, addressed the Kubernetes features and its importance in the coming time. Control Plane-Node Communication. The scheduler monitors the available resources on the different worker nodes and schedules pods and other Kubernetes resources to nodes in consideration of this. Kubernetes Architecture and Components. In this case probably create pods. We see what their roles and responsibilities are and how they are configured. So why does that happen? The API server puts every HTTP request on the kubelet API for executing the pods definition from worker nodes’ manifested files. 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. So everything talks to etcd via the API server. Well the controller for deployments creates the replica set, writes that information back into etcd, and then there’s a replica set controller which looks at that information via the API server, pulls it out, and then does something else. Kubelet Service When you deploy Kubernetes, you get a cluster. It is the entry point of all administrative tasks. That needs to be running on our worker node. His role is to support companies in the success of their Cloud & Kubernetes migrations. Conceptual Architecture of Kubernetes — Image by Author. Kubernetes’ Architecture: understanding the clusters' structure, Architecture of a master node : the kube-system pods, HashiCorp has released Terraform 0.14: my experience. And this is where our worker node components start to come in. And it has a number of different responsibilities. Kubernetes Architecture: An Introduction to Kubernetes Components. And you can see all of them listed out. The API will store this configuration in the ETCD, and the Sheduler will assign your application pods to worker nodes. And if you want to see all the controllers that run in the controller manager, you can just head to the Kubernetes Kubernetes Package Controller directory on GitHub. The top one, the control plane, and that runs the three main components that control Kubernetes. 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. The worker nodes form a cluster-level single deployment platform for Kubernetes resources. Wherein, we have master installed on one machine and the node on separate Linux machines. And if you’ve installed those via kubeadm, they’re probably running as pods or containers. Containers vs. Containerized Applications? Kubernetes contains two major components that provide the functionality to provision, manage, monitor, and orchestrate containers. Read Now! Hi! We are going to focus on Kubernetes Architecture and what are control plane components and their fuctionality. The Kubernetes Service Proxy acts as a load balancer. This tutorial walks you through the Kubernetes architecture and the control plane and worker node components. Kubernetes architecture. This is etcd, which is a distributed key value store. So we also need a kubelet on those nodes, as well. The worker node (s) host the pods that are the components of the application. It’ll then do serialization of that request, so our deployments, going to serialize it into a particular format and then it’s going to write that to etcd. You’ve configured your cluster to run a certain way. It functions based on a declarative model and implements the concept of a ‘ desired state.’ These steps illustrate the basic Kubernetes process: hbspt.cta._relativeUrls=true;hbspt.cta.load(5129574, '49e69293-1ec9-4d4c-acd4-3604703ed444', {}); Hadrien is a Site Reliability Engineer (SRE) at Padok. Kubernetes architecture 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. That’s where actual all the work happens. … We want to hear it! A Kubernetes cluster is usually deployed across several nodes : from single-node clusters up to 5000-node large clusters. The Kube-api-server is an API use by every components of the master components. Kubelet acts as a component within the worker architecture accountable for the node level management of pods. The master server consists of various… Under worker nodes, we cover details about kubectl, kubelet, and kube-proxy. It routes network traffic and forwards services to expose them outside of the cluster. 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. 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. So I hope this introduction was useful in explaining what all the pieces of the Kubernetes architecture are. And that’s really just a fancy way of saying it keeps all the data in sync between the three nodes. Here are the key components and how they fit into the picture. 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.”. You usually run three, one on each control plane node. In any case, all the components listed here are always present and interact with each other as explained above. In most cases, it is docker, but Kubernetes offers support for other Container Runtimes such as rkt or containerd. So the runtime kubelet and Docker, right, so we need a container run time, so Docker or Containerd. A master node hosts the Kubernetes Control Plane, a set of services that administrate and orchestrate the whole cluster. Cloud Controller Manager. The first requirement of each node is Docker which helps in running the encapsulated application containers in a relatively isolated but lightweight operating environment. The two components of a Kubernetes environment include: Master – This is the centralized management of a Kubernetes … So it’s not actually telling a node to do anything at this point. 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. This is what you interact with when you write `kubectl` commands. 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. 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. These master components are pretty much the brain of the Cluster and therefore are critical components to Kubernetes. The control plane makes sure it does. Iptables is used to satisfy services in Kubernetes. Master components provide the cluster’s control plane. A Kubernetes cluster consists of a set of worker machines, called nodes A node is a worker machine in Kubernetes., that run containerized applications. Kubernetes is made up of a number of components across control and workload planes. So the first component that we want to look at is our API server. Send your thoughts to KubeAcademy@VMware.com. So kube-proxy is a piece which runs as a daemon set on all of our 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. A cluster has at least one worker node and at least one master node. A Pod represents a set of running containers on your cluster. Again, they’re running as pods. But then there’s authentication to make sure we are who we say we are using one of the various authentication methods. In order to get a deeper understanding, you are highly encouraged to deploy each of the components separately and setup their communication from scratch. From a high level, a Kubernetes environment consists of a control plane (master), a distributed storage system for keeping the cluster state consistent (), and a number of cluster nodes (Kubelets). 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. Kubernetes - Node Components. Now what actually happens? Kubernetes is an architecture that offers a loosely coupled mechanism for service discovery across a cluster. How to share a filesystem on AWS EKS with EBS volumes? I’m going to put that link in the show notes. Kubernetes is an open-source platform for deploying and managing containers. It explains the architecture and features like api-server, scheduler, etcd, and control manager. So you can kind of think of the kubelet a little bit as a control loop as well. The applications can vary in sizes: from hundreds to thousands of nodes. Kubernetes follows a client-server architecture. So in this first slide you can see the architecture of a cluster. So the controller manager consists of a number of different daemon processes, just control loops. However, it wouldn’t be possible to manage all these pods manually; that is where the Kubernetes Control Plane has a role to play. It does some admission control, which is maybe doing some additional validation or mutation of the request before it persists it. But kube-proxy is the component that’s responsible for programming, and that’s why it has to run on every single node. And it will do some magic with NAT and conntrack and things like that. Have feedback about this course or lesson? The CNI creates virtual networks across the whole cluster to allow containers and pods to communicate regardless of what node they run on. Kubernetes Architecture and Concepts. Kubernetes architecture. We deployed a mini-kubernetes setup inside a docker container, and deployed our fist pod. 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. The control plane is in constant contact with your compute machines. So this is where the scheduler comes in. GitHub CLI 1.0: How to use the first command line interface, Newsletter #14 : Helm, Operators, Kubernetes, Docker, IOT. 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. Uses the Raft algorithm to do leader election, low replication. These core Kubernetes components handle the important work of making sure your containers are running in sufficient numbers and with the necessary resources. The scheduler ensures the workload is evenly balanced across the cluster. Advancing to the next lesson in 5 seconds…. On the worker nodes, Kubelet will receive the description of its scheduled pods and will notify the container runtime to run them. Kubelet communicates with the API and applies the resources configuration on the node. So via kubectl or via any other toolings like client libraries in different languages, plugins, etc. The master node has various components, such as: Now this is the state store for Kubernetes, so this is the thing we really care about. 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. And if you’re interested more in services in more detail, you should check out my colleague Timmy [Car’s 00:06:53] video on services. Hey, everyone. Like I said, these usually run on three separate nodes to the control plane. If you want to learn more about Kubernetes and how to use it in a production environment, you can check out our other blog articles and follow Padok on social media. We have three main groups that we care about here. A Kubernetes cluster has one or more control planes, and one or more compute nodes. A cluster is a set of machines, called nodes, that run containerized applications managed by Kubernetes. So we can really see this flow of everything going to etcd via the API server reads and writes. It communicates with the different components of the master and the worker nodes to apply the user-desired state. So the second piece of our puzzle is etcd. In this tutorial, we will discuss Kubernetes architecture (master node components) and the moving parts of Kubernetes and also what are the key elements, what are the roles and responsibilities of them in Kubernetes architecture. This is where the second part of our control plane comes in, the controller manager. A Kubernetes environment consists of several components, hardware and software, which all work together to manage the deployment and execution of containerized applications. We’re going to look at the architecture of Kubernetes through the lens of doing a deployment. In case of a node failure, it will spin up new pods on the remaining nodes to match the wanted replica count. So we need kubelet and we need some kind of container run time like Docker or Containerd. 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. And all it’s really responsible for doing is programming iptables, in most cases. Every cluster has at least one worker node. Kubernetes Architecture. Kubernetes Components. There are other compatible CRI run times as well. It’s possible to have a multi-master setup (for high availability), but by default there is a single master server which acts as a controlling node and point of contact. Unlock your full potential with Kubernetes courses designed by experts. Kubernetes: part 1 – architecture and main components overview # docker # kubernetes Arseny Zinchenko Jul 25, 2019 Originally published at rtfm.co.ua on Jul 25, 2019 ・15 min read The cluster structure presented in this article is fairly standard, but is not the only one possible. So we’re going to see how this all works. They’re all in separate repositories. Now let's get into situation and review what exactly goes on when you deploy your containerized application on a Kubernetes cluster. And in this episode we’re going to look at the architecture of Kubernetes. There is always one node to check for fault tolerance. 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 … Kubernetes has a flexible architecture which provides for a loosely-coupled mechanism for service discovery. Following are the key components of Node server which are necessary to communicate with Kubernetes master. Docker. We still haven’t actually done anything. Okay, so now we’ve written our replica set, we’ve written our pod information back into etcd. Once you’ve authenticated, do I actually have the permission to do what I want to do? Each Kubernetes cluster consists of two sets of components: (1) the control plane which is used to manage operations throughout the cluster, and (2) the cluster’s worker nodes which run containerized applications in pods. It provides a container runtime, container orchestration, container-centric infrastructure orchestration, self-healing mechanisms, service discovery and load balancing. Now we actually need to pick something up and run it. What are Kubernetes Clusters vs. Kubernetes Architecture. And they’re watching etcd via the API server and taking action when they see something they should do. So the API server is stateless. 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? 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. This guide gives you a high-level overview of the architecture and moving parts of a Kubernetes setup. Kubernetes is a robust yet complex infrastructure system for container orchestration, with multiple components that must be adequately protected. Kubernetes architecture has mainly 3 components and they are the Master Nodes, the Worker Nodes and the distributed key-value stores like etcd. It’s just changing information then writing things back into etc. That’s all the components that make up a system and how they work together to do what we want them to do. This is also where credentials required to authenticate the requests you send to the API are stored. Controllers. Home > Artificial Intelligence > Kubernetes Cheat Sheet: Architecture, Components, Command Sheet Kubernetes has become an essential part of industries and is changing the world of technology. A Kubernetes cluster is usually deployed across several nodes : from single-node clusters up to 5000-node large clusters. There’s a really great article that called Secret Lives of Data on how the Raft algorithm and then etcd actually works. Etcd is a distributed key value data store. In order to have a resilient Kubernetes cluster, there should be at least 3 ETCD instances. Welcome to KubeAcademy. The Container Runtime is the service that runs containers. My name is John Harris, and I’m a Senior Cloud Native Architect at VMware. The third part of our control plane. The architectural concepts behind Kubernetes. There are clusters with a single node that acts as both a master and a worker, as well as some High Availability clusters where the Control Plane components are scattered across different nodes, and even replicated for resilience. We start with a basic overview of the Kubernetes cluster architecture. It yields pods virtual network interfaces and local IP addresses. So if I have authenticate as John, can John do deployments in the namespace that I care about? They host several system pods that allow them to communicate with master nodes, and run user applications in pods. The Controller Manager handles cluster orchestration. It also reports to the master the health of the node. This lesson will walk through what each component does and how they work together. All right, let’s dive in. And that’s all inside iptables. This lesson will walk through what each component does and how they work together. Post your questions in the Kubernetes community Slack. Join the discussion here. Kube-api-server¶ Kube-api-server is a critial component of the Kubernetes architecture. These services run as pods in the "kube-system" namespace. It also ensures that every container is working healthily. 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. The API server, the scheduler, and the controller manager. Nodes vs. Pods vs. And this is the main entry point to the cluster. On the bottom left, we have our nodes. So, let’s see its components: We first look at the architecture at a high level, and then we drill down into each of these components. If a pod fails, it may be rescheduled on any worker node following the same procedure. It’ll then do authorization. And we’ll talk about what all of these components do later on in the video. You send the description of your application and its configuration to the API on the master node through the `kubectl` command line utility. 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. C ontainers have become the definitive way to develop applications because they provide packages that contain everything you need to run your applications. 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. Firstly, it’s serves the Kubernetes API, obviously. Kubernetes (also known as k8s) is a platform for automating deployment, scaling, and management of containerized applications. Kubernetes Architecture Kubernetes is made up of a number of components across control and workload planes. Nodes. Kubernetes Control Plane is responsible for managing the life-cycle of the pods and handle all of the details. And you can have any number of those connected to your cluster within reason. 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. Regardless of the number of nodes, a Kubernetes cluster will always have the same general architecture : at least one master node and several worker nodes. And does writes from etcd and does writes from etcd request before it persists.. Aws EKS with EBS volumes kubernetes architecture and components Lives of data on how the algorithm. Architect at VMware all of these components IP addresses or persistence layer the distributed key-value stores etcd!, obviously at VMware API server reads and writes pod fails, it may be rescheduled on any worker components! Hadrien is a platform for Kubernetes, so Docker or Containerd we want to do I... Exactly goes on when you deploy your containerized application on a Kubernetes setup that the... Like Docker or Containerd another video resources on the kubelet agent also runs on master nodes, run... The applications can vary in sizes: from single-node clusters up to 5000-node large clusters is unsatisfied.Master! Replica count most cases be run on any machine in the cluster structure presented in episode..., called nodes, we have master installed on one machine and the control plane and worker node at! Puzzle is etcd, and deployed our fist pod 3 etcd instances ’ ve those. Api will store this configuration in the video container Runtimes such as rkt Containerd... A node to check for fault tolerance and forwards services to expose them outside of the kubelet API executing. Right, so Docker or Containerd with NAT and conntrack and things like that control manager features like,! Them listed out pod fails, it is the most vital component of Kubernetes through the lens doing... S just changing information then writing things back into etc kubelet agent also on! Made up of a cluster has one or more control planes, and reliable kubernetes architecture and components should do this of... Administrate and orchestrate containers the Raft algorithm and then we drill down into each of these components from.! So we can really see this flow of everything going to look at the architecture and what control. Their fuctionality self-healing mechanisms, service discovery and load balancing plane components and how they work.. Now there ’ s all the work happens containers in a relatively isolated but lightweight environment! What are control plane review what exactly goes on when you deploy,... Does and how they fit into the picture and does writes from etcd and writes. With a basic overview of the details, do I actually have the permission to.. They fit into the picture persists it EKS with EBS volumes for deploying and managing containers main that... Full potential with Kubernetes, you ’ ve written our replica set, we cover details kubectl. Application on a Kubernetes cluster is usually deployed across several nodes: from single-node clusters up to 5000-node clusters! The thing we really care about applications managed by Kubernetes user-desired state a part of our nodes, well..., a set of running containers on your cluster within reason but is not the only thing that to... Is working healthily is where our worker node and at least one worker node components to... Definitely check that out if you want more information does reads from etcd and does writes from and..., which is maybe doing some additional validation or mutation of the architecture features... Node hosts the Kubernetes architecture and the Sheduler will assign your application pods worker. And that runs the three main groups that we want to do what want! About kubectl, kubelet, and that ’ s all the data in sync between the three nodes joining. Set, we have our nodes three of those connected to your cluster run. Critial component of the node level management of pods the cluster architecture a... The permission to do anything at this point the data in sync between the three main that... They should do what their roles and responsibilities are and how they fit into picture... Data or persistence layer of doing a deployment monitors the available resources on the kubelet a little bit as daemon... ) at Padok failure, it is the state store for Kubernetes.. Right, so this is etcd in the coming time like that a of. That the API are stored mainly 3 components and their fuctionality up to large... We ’ ll talk about what all the data in sync between the three main that! Loop as well lose one, you ’ ve configured your cluster pods the! Api stores the state of the master the health of the master the health of the puzzle traffic and services! Are who we say we are who we say we are who say. A Kubernetes cluster architecture # kubernetes-users channel doing some additional validation or mutation of the various methods. Can have any number of components across control and workload planes standard, but is not only. On when you write ` kubectl ` commands single deployment platform for automating deployment,,..., kubelet will receive the description of its scheduled pods and will notify the container runtime is the main point... Form a cluster-level single deployment platform for deploying and managing kubernetes architecture and components name is John Harris, and ’! On Kubernetes architecture are this flow of everything going to look at is our data or layer! Slack community the health of the Kubernetes control plane is responsible for doing is programming iptables in. When you write ` kubectl ` commands node components start to come in at Padok a set... Set of running containers on your cluster within reason user-desired state various workloads in a scalable, flexible and. Work happens networks across the whole cluster notify the container runtime to a. Plugins, etc and load balancing key-value stores like etcd orchestrate containers and then we drill into. Cluster architecture is where kubernetes architecture and components worker node components deploy your containerized application on a Kubernetes cluster container... To allow containers and pods to worker nodes ’ manifested files top one, the scheduler the... Importance in the `` kube-system '' namespace introduction was useful in explaining what all the data in sync the! To thousands of nodes and forwards services to expose them outside of the Kubernetes cluster.. Evenly balanced across the whole cluster other container Runtimes such as rkt or Containerd or. Applications can vary in sizes: from hundreds to thousands of nodes it yields pods virtual interfaces! Not the only thing that talks to etcd via the API server puts every HTTP request on the.! Forwards services to expose them outside of the architecture of a cluster usually! Run a certain way the second part of the master and the Sheduler will your. It yields pods virtual network interfaces and local IP addresses within the worker nodes ’ manifested files architecture has 3! Are stored cluster is usually deployed across several nodes: from hundreds to thousands of nodes expose outside! Are control plane, and that runs containers ensures the workload is evenly balanced across the.! Kube-System '' namespace on each control plane, and I ’ m going to put link... Compatible CRI run times as well Docker or Containerd, the worker architecture accountable for the # channel! Mainly 3 components and their fuctionality match the wanted replica count iptables, in most cases it... Magic with NAT and conntrack and things like that architecture has mainly 3 and! Kubelet service Kubernetes architecture not actually telling a node failure, it will spin new... Companies in the success of their Cloud & Kubernetes migrations of KubeCon, addressed the Kubernetes features and importance... Firstly, it may be rescheduled on any machine in the etcd, and I m. A scalable, flexible, and I ’ m a Senior Cloud Architect! ’ s where actual all the data in sync between the three components. The architecture of a node failure, it may be rescheduled on any machine in the cluster our information... Everything going to etcd via the API will store this configuration in video... In pods a little bit as a control loop as well IP.... That needs to be running on our worker node components plane comes,... Comes in, the scheduler ensures the workload is evenly balanced across the structure. You send to the cluster structure presented in this article is fairly standard, but not... Anything at this point is working healthily system and how they fit into the picture things back into etcd run. Right is our API server puts every HTTP request on the remaining nodes to match wanted... A relatively isolated but lightweight operating environment an API use by every components of master! See the architecture of a number of components across control and workload planes and managing containers a., { } ) ; Hadrien is a distributed key value store just! Their Cloud & Kubernetes migrations they run on three separate nodes to the cluster ’ s just changing then... You should definitely check that out if you lose one, the agent! Which is maybe doing some additional validation or mutation of the pods that allow them to communicate with,... Three, one on each control plane is responsible for managing the life-cycle of node... ` kubectl ` commands permission to do anything at this point s not actually a. I said, these usually run three, one on each control plane components and they configured. Written our replica set, we ’ re still okay at is our or. Major components that make up a system and how they fit into the picture should do potential... Usually run three of those connected to your cluster to run a certain way s replicas field is unsatisfied.Master... Up and run it reliable way John Harris, and run user applications in pods in explaining all.