From b80f5e4e6f3aa1fda6dd5bc56e47b13399146a3e Mon Sep 17 00:00:00 2001 From: Andrei Kvapil Date: Tue, 16 Apr 2024 11:19:22 +0200 Subject: [PATCH] Add our articles from kubernetes.io (#10) --- .../asciicast.svg | 497 ++++++++++++++++++ .../baremetal.svg | 60 +++ .../cloud.svg | 67 +++ .../index.md | 255 +++++++++ .../index.md | 264 ++++++++++ .../kata-containers.svg | 281 ++++++++++ .../kubevirt-migration.svg | 172 ++++++ .../net-loadbalancer.svg | 136 +++++ .../net-nodes.svg | 124 +++++ .../net-pods.svg | 131 +++++ .../net-services.svg | 133 +++++ .../storage-clustered.svg | 213 ++++++++ .../storage-external.svg | 219 ++++++++ .../storage-local.svg | 309 +++++++++++ .../clusterapi1.svg | 41 ++ .../clusterapi2.svg | 29 + .../clusterapi3.svg | 29 + .../components1.svg | 42 ++ .../components2.svg | 67 +++ .../components3.svg | 97 ++++ .../components4.svg | 66 +++ .../fluxcd.svg | 48 ++ .../index.md | 271 ++++++++++ .../machinedeploymentres.svg | 25 + 24 files changed, 3576 insertions(+) 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b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-1/index.md new file mode 100644 index 0000000..30fa032 --- /dev/null +++ b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-1/index.md @@ -0,0 +1,255 @@ +--- +layout: blog +title: "DIY: Create Your Own Cloud with Kubernetes (Part 1)" +slug: diy-create-your-own-cloud-with-kubernetes-part-1 +date: 2024-04-05T07:30:00+00:00 +--- + +**Author**: Andrei Kvapil (Ænix) + +At Ænix, we have a deep affection for Kubernetes and dream that all modern technologies will soon +start utilizing its remarkable patterns. + +Have you ever thought about building your own cloud? I bet you have. But is it possible to do this +using only modern technologies and approaches, without leaving the cozy Kubernetes ecosystem? +Our experience in developing Cozystack required us to delve deeply into it. + +You might argue that Kubernetes is not intended for this purpose and why not simply use OpenStack +for bare metal servers and run Kubernetes inside it as intended. But by doing so, you would simply + shift the responsibility from your hands to the hands of OpenStack administrators. + This would add at least one more huge and complex system to your ecosystem. + +Why complicate things? - after all, Kubernetes already has everything needed to run tenant +Kubernetes clusters at this point. + +I want to share with you our experience in developing a cloud platform based on Kubernetes, +highlighting the open-source projects that we use ourselves and believe deserve your attention. + +In this series of articles, I will tell you our story about how we prepare managed Kubernetes +from bare metal using only open-source technologies. Starting from the basic level of data +center preparation, running virtual machines, isolating networks, setting up fault-tolerant +storage to provisioning full-featured Kubernetes clusters with dynamic volume provisioning, +load balancers, and autoscaling. + +With this article, I start a series consisting of several parts: + +- **Part 1**: Preparing the groundwork for your cloud. Challenges faced during the preparation +and operation of Kubernetes on bare metal and a ready-made recipe for provisioning infrastructure. +- **Part 2**: Networking, storage, and virtualization. How to turn Kubernetes into a tool for +launching virtual machines and what is needed for this. +- **Part 3**: Cluster API and how to start provisioning Kubernetes clusters at the push of a +button. How autoscaling works, dynamic provisioning of volumes, and load balancers. + +I will try to describe various technologies as independently as possible, but at the same time, +I will share our experience and why we came to one solution or another. + +To begin with, let's understand the main advantage of Kubernetes and how it has changed the +approach to using cloud resources. + +It is important to understand that the use of Kubernetes in the cloud and on bare metal differs. + +## Kubernetes in the cloud + +When you operate Kubernetes in the cloud, you don't worry about persistent volumes, +cloud load balancers, or the process of provisioning nodes. All of this is handled by your cloud +provider, who accepts your requests in the form of Kubernetes objects. In other words, the server +side is completely hidden from you, and you don't really want to know how exactly the cloud +provider implements as it's not in your area of responsibility. + +{{< figure src="cloud.svg" alt="A diagram showing cloud Kubernetes, with load balancing and storage done outside the cluster" caption="A diagram showing cloud Kubernetes, with load balancing and storage done outside the cluster" >}} + +Kubernetes offers convenient abstractions that work the same everywhere, allowing you to deploy +your application on any Kubernetes in any cloud. + +In the cloud, you very commonly have several separate entities: the Kubernetes control plane, +virtual machines, persistent volumes, and load balancers as distinct entities. Using these entities, you can create highly dynamic environments. + +Thanks to Kubernetes, virtual machines are now only seen as a utility entity for utilizing +cloud resources. You no longer store data inside virtual machines. You can delete all your virtual +machines at any moment and recreate them without breaking your application. The Kubernetes control +plane will continue to hold information about what should run in your cluster. The load balancer +will keep sending traffic to your workload, simply changing the endpoint to send traffic to a new +node. And your data will be safely stored in external persistent volumes provided by cloud. + +This approach is fundamental when using Kubernetes in clouds. The reason for it is quite obvious: +the simpler the system, the more stable it is, and for this simplicity you go buying Kubernetes +in the cloud. + +## Kubernetes on bare metal + +Using Kubernetes in the clouds is really simple and convenient, which cannot be said about bare +metal installations. In the bare metal world, Kubernetes, on the contrary, becomes unbearably +complex. Firstly, because the entire network, backend storage, cloud balancers, etc. are usually +run not outside, but inside your cluster. As result such a system is much more difficult to +update and maintain. + +{{< figure src="baremetal.svg" alt="A diagram showing bare metal Kubernetes, with load balancing and storage done inside the cluster" caption="A diagram showing bare metal Kubernetes, with load balancing and storage done inside the cluster" >}} + + +Judge for yourself: in the cloud, to update a node, you typically delete the virtual machine +(or even use `kubectl delete node`) and you let your node management tooling create a new +one, based on an immutable image. The new node will join the cluster and ”just work” as a node; +following a very simple and commonly used pattern in the Kubernetes world. +Many clusters order new virtual machines every few minutes, simply because they can use +cheaper spot instances. However, when you have a physical server, you can't just delete and +recreate it, firstly because it often runs some cluster services, stores data, and its update process +is significantly more complicated. + +There are different approaches to solving this problem, ranging from in-place updates, as done by +kubeadm, kubespray, and k3s, to full automation of provisioning physical nodes through Cluster API +and Metal3. + +I like the hybrid approach offered by Talos Linux, where your entire system is described in a +single configuration file. Most parameters of this file can be applied without rebooting or +recreating the node, including the version of Kubernetes control-plane components. However, it +still keeps the maximum declarative nature of Kubernetes. +This approach minimizes unnecessary impact on cluster services when updating bare metal nodes. +In most cases, you won't need to migrate your virtual machines and rebuild the cluster filesystem +on minor updates. + +## Preparing a base for your future cloud + +So, suppose you've decided to build your own cloud. To start somewhere, you need a base layer. +You need to think not only about how you will install Kubernetes on your servers but also about how +you will update and maintain it. Consider the fact that you will have to think about things like +updating the kernel, installing necessary modules, as well packages and security patches. +Now you have to think much more that you don't have to worry about when using a ready-made +Kubernetes in the cloud. + +Of course you can use standard distributions like Ubuntu or Debian, or you can consider specialized +ones like Flatcar Container Linux, Fedora Core, and Talos Linux. Each has its advantages and +disadvantages. + +What about us? At Ænix, we use quite a few specific kernel modules like ZFS, DRBD, and OpenvSwitch, +so we decided to go the route of forming a system image with all the necessary modules in advance. +In this case, Talos Linux turned out to be the most convenient for us. +For example, such a config is enough to build a system image with all the necessary kernel modules: + +```yaml +arch: amd64 +platform: metal +secureboot: false +version: v1.6.4 +input: + kernel: + path: /usr/install/amd64/vmlinuz + initramfs: + path: /usr/install/amd64/initramfs.xz + baseInstaller: + imageRef: ghcr.io/siderolabs/installer:v1.6.4 + systemExtensions: + - imageRef: ghcr.io/siderolabs/amd-ucode:20240115 + - imageRef: ghcr.io/siderolabs/amdgpu-firmware:20240115 + - imageRef: ghcr.io/siderolabs/bnx2-bnx2x:20240115 + - imageRef: ghcr.io/siderolabs/i915-ucode:20240115 + - imageRef: ghcr.io/siderolabs/intel-ice-firmware:20240115 + - imageRef: ghcr.io/siderolabs/intel-ucode:20231114 + - imageRef: ghcr.io/siderolabs/qlogic-firmware:20240115 + - imageRef: ghcr.io/siderolabs/drbd:9.2.6-v1.6.4 + - imageRef: ghcr.io/siderolabs/zfs:2.1.14-v1.6.4 +output: + kind: installer + outFormat: raw +``` + +Then we use the `docker` command line tool to build an OS image: + +``` +cat config.yaml | docker run --rm -i -v /dev:/dev --privileged "ghcr.io/siderolabs/imager:v1.6.4" - +``` + +And as a result, we get a Docker container image with everything we need, which we can use to +install Talos Linux on our servers. You can do the same; this image will contain all the necessary +firmware and kernel modules. + +But the question arises, how do you deliver the freshly formed image to your nodes? + +I have been contemplating the idea of PXE booting for quite some time. For example, the +**Kubefarm** project that I wrote an +[article](/blog/2021/12/22/kubernetes-in-kubernetes-and-pxe-bootable-server-farm/) about +two years ago was entirely built using this approach. But unfortunately, it does help you to +deploy your very first parent cluster that will hold the others. So now you have prepared a +solution that will help you do this the same using PXE approach. + +Essentially, all you need to do is [run temporary](https://cozystack.io/docs/get-started/) +**DHCP** and **PXE** servers inside containers. Then your nodes will boot from your +image, and you can use a simple Debian-flavored script to help you bootstrap your nodes. + +[![asciicast](asciicast.svg)](https://asciinema.org/a/627123) + +The [source](https://github.com/aenix-io/talos-bootstrap/) for that `talos-bootstrap` script is +available on GitHub. + +This script allows you to deploy Kubernetes on bare metal in five minutes and obtain a kubeconfig +for accessing it. However, many unresolved issues still lie ahead. + +## Delivering system components + +At this stage, you already have a Kubernetes cluster capable of running various workloads. However, +it is not fully functional yet. In other words, you need to set up networking and storage, as well +as install necessary cluster extensions, like KubeVirt to run virtual machines, as well the +monitoring stack and other system-wide components. + +Traditionally, this is solved by installing **Helm charts** into your cluster. You can do this by +running `helm install` commands locally, but this approach becomes inconvenient when you want to +track updates, and if you have multiple clusters and you want to keep them uniform. In fact, there +are plenty of ways to do this declaratively. To solve this, I recommend using best GitOps practices. +I mean tools like ArgoCD and FluxCD. + +While ArgoCD is more convenient for dev purposes with its graphical interface and a central control +plane, FluxCD, on the other hand, is better suited for creating Kubernetes distributions. With FluxCD, +you can specify which charts with what parameters should be launched and describe dependencies. Then, +FluxCD will take care of everything for you. + +It is suggested to perform a one-time installation of FluxCD in your newly created cluster and +provide it with the configuration. This will install everything necessary, bringing the cluster +to the expected state. + +By carrying out a single installation of FluxCD in your newly minted cluster and configuring it +accordingly, you enable it to automatically deploy all the essentials. This will allow your cluster +to upgrade itself into the desired state. For example, after installing our platform you'll see the +next pre-configured Helm charts with system components: + +``` +NAMESPACE NAME AGE READY STATUS +cozy-cert-manager cert-manager 4m1s True Release reconciliation succeeded +cozy-cert-manager cert-manager-issuers 4m1s True Release reconciliation succeeded +cozy-cilium cilium 4m1s True Release reconciliation succeeded +cozy-cluster-api capi-operator 4m1s True Release reconciliation succeeded +cozy-cluster-api capi-providers 4m1s True Release reconciliation succeeded +cozy-dashboard dashboard 4m1s True Release reconciliation succeeded +cozy-fluxcd cozy-fluxcd 4m1s True Release reconciliation succeeded +cozy-grafana-operator grafana-operator 4m1s True Release reconciliation succeeded +cozy-kamaji kamaji 4m1s True Release reconciliation succeeded +cozy-kubeovn kubeovn 4m1s True Release reconciliation succeeded +cozy-kubevirt-cdi kubevirt-cdi 4m1s True Release reconciliation succeeded +cozy-kubevirt-cdi kubevirt-cdi-operator 4m1s True Release reconciliation succeeded +cozy-kubevirt kubevirt 4m1s True Release reconciliation succeeded +cozy-kubevirt kubevirt-operator 4m1s True Release reconciliation succeeded +cozy-linstor linstor 4m1s True Release reconciliation succeeded +cozy-linstor piraeus-operator 4m1s True Release reconciliation succeeded +cozy-mariadb-operator mariadb-operator 4m1s True Release reconciliation succeeded +cozy-metallb metallb 4m1s True Release reconciliation succeeded +cozy-monitoring monitoring 4m1s True Release reconciliation succeeded +cozy-postgres-operator postgres-operator 4m1s True Release reconciliation succeeded +cozy-rabbitmq-operator rabbitmq-operator 4m1s True Release reconciliation succeeded +cozy-redis-operator redis-operator 4m1s True Release reconciliation succeeded +cozy-telepresence telepresence 4m1s True Release reconciliation succeeded +cozy-victoria-metrics-operator victoria-metrics-operator 4m1s True Release reconciliation succeeded +``` + +## Conclusion + +As a result, you achieve a highly repeatable environment that you can provide to anyone, knowing +that it operates exactly as intended. +This is actually what the [Cozystack](https://github.com/aenix-io/cozystack) project does, which +you can try out for yourself absolutely free. + +In the following articles, I will discuss +[how to prepare Kubernetes for running virtual machines](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-2/) +and [how to run Kubernetes clusters with the click of a button](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-3/). +Stay tuned, it'll be fun! + +--- + +*Originally published at [https://kubernetes.io](https://kubernetes.io/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-1/) on April 5, 2024.* diff --git a/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-2/index.md b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-2/index.md new file mode 100644 index 0000000..58993d2 --- /dev/null +++ b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-2/index.md @@ -0,0 +1,264 @@ +--- +layout: blog +title: "DIY: Create Your Own Cloud with Kubernetes (Part 2)" +slug: diy-create-your-own-cloud-with-kubernetes-part-2 +date: 2024-04-05T07:35:00+00:00 +--- + +**Author**: Andrei Kvapil (Ænix) + +Continuing our series of posts on how to build your own cloud using just the Kubernetes ecosystem. +In the [previous article](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-1/), we +explained how we prepare a basic Kubernetes distribution based on Talos Linux and Flux CD. +In this article, we'll show you a few various virtualization technologies in Kubernetes and prepare +everything need to run virtual machines in Kubernetes, primarily storage and networking. + +We will talk about technologies such as KubeVirt, LINSTOR, and Kube-OVN. + +But first, let's explain what virtual machines are needed for, and why can't you just use docker +containers for building cloud? +The reason is that containers do not provide a sufficient level of isolation. +Although the situation improves year by year, we often encounter vulnerabilities that allow +escaping the container sandbox and elevating privileges in the system. + +On the other hand, Kubernetes was not originally designed to be a multi-tenant system, meaning +the basic usage pattern involves creating a separate Kubernetes cluster for every independent +project and development team. + +Virtual machines are the primary means of isolating tenants from each other in a cloud environment. +In virtual machines, users can execute code and programs with administrative privilege, but this +doesn't affect other tenants or the environment itself. In other words, virtual machines allow to +achieve [hard multi-tenancy isolation](/docs/concepts/security/multi-tenancy/#isolation), and run +in environments where tenants do not trust each other. + +## Virtualization technologies in Kubernetes + +There are several different technologies that bring virtualization into the Kubernetes world: +[KubeVirt](https://kubevirt.io/) and [Kata Containers](https://katacontainers.io/) +are the most popular ones. But you should know that they work differently. + +**Kata Containers** implements the CRI (Container Runtime Interface) and provides an additional +level of isolation for standard containers by running them in virtual machines. +But they work in a same single Kubernetes-cluster. + +{{< figure src="kata-containers.svg" caption="A diagram showing how container isolation is ensured by running containers in virtual machines with Kata Containers" alt="A diagram showing how container isolation is ensured by running containers in virtual machines with Kata Containers" >}} + +**KubeVirt** allows running traditional virtual machines using the Kubernetes API. KubeVirt virtual +machines are run as regular linux processes in containers. In other words, in KubeVirt, a container +is used as a sandbox for running virtual machine (QEMU) processes. +This can be clearly seen in the figure below, by looking at how live migration of virtual machines +is implemented in KubeVirt. When migration is needed, the virtual machine moves from one container +to another. + +{{< figure src="kubevirt-migration.svg" caption="A diagram showing live migration of a virtual machine from one container to another in KubeVirt" alt="A diagram showing live migration of a virtual machine from one container to another in KubeVirt" >}} + +There is also an alternative project - [Virtink](https://github.com/smartxworks/virtink), which +implements lightweight virtualization using +[Cloud-Hypervisor](https://github.com/cloud-hypervisor/cloud-hypervisor) and is initially focused +on running virtual Kubernetes clusters using the Cluster API. + +Considering our goals, we decided to use KubeVirt as the most popular project in this area. +Besides we have extensive expertise and already made a lot of contributions to KubeVirt. + +KubeVirt is [easy to install](https://kubevirt.io/user-guide/operations/installation/) and allows +you to run virtual machines out-of-the-box using +[containerDisk](https://kubevirt.io/user-guide/virtual_machines/disks_and_volumes/#containerdisk) +feature - this allows you to store and distribute VM images directly as OCI images from container +image registry. +Virtual machines with containerDisk are well suited for creating Kubernetes worker nodes and other +VMs that do not require state persistence. + +For managing persistent data, KubeVirt offers a separate tool, Containerized Data Importer (CDI). +It allows for cloning PVCs and populating them with data from base images. The CDI is necessary +if you want to automatically provision persistent volumes for your virtual machines, and it is + also required for the KubeVirt CSI Driver, which is used to handle persistent volumes claims + from tenant Kubernetes clusters. + +But at first, you have to decide where and how you will store these data. + +## Storage for Kubernetes VMs + +With the introduction of the CSI (Container Storage Interface), a wide range of technologies that +integrate with Kubernetes has become available. +In fact, KubeVirt fully utilizes the CSI interface, aligning the choice of storage for +virtualization closely with the choice of storage for Kubernetes itself. +However, there are nuances, which you need to consider. Unlike containers, which typically use a +standard filesystem, block devices are more efficient for virtual machine. + +Although the CSI interface in Kubernetes allows the request of both types of volumes: filesystems +and block devices, it's important to verify that your storage backend supports this. + +Using block devices for virtual machines eliminates the need for an additional abstraction layer, +such as a filesystem, that makes it more performant and in most cases enables the use of the +_ReadWriteMany_ mode. This mode allows concurrent access to the volume from multiple nodes, which +is a critical feature for enabling the live migration of virtual machines in KubeVirt. + +The storage system can be external or internal (in the case of hyper-converged infrastructure). +Using external storage in many cases makes the whole system more stable, as your data is stored +separately from compute nodes. + +{{< figure src="storage-external.svg" caption="A diagram showing external data storage communication with the compute nodes" alt="A diagram showing external data storage communication with the compute nodes" >}} + +External storage solutions are often popular in enterprise systems because such storage is +frequently provided by an external vendor, that takes care of its operations. The integration with +Kubernetes involves only a small component installed in the cluster - the CSI driver. This driver +is responsible for provisioning volumes in this storage and attaching them to pods run by Kubernetes. +However, such storage solutions can also be implemented using purely open-source technologies. +One of the popular solutions is [TrueNAS](https://www.truenas.com/) powered by +[democratic-csi](https://github.com/democratic-csi/democratic-csi) driver. + +{{< figure src="storage-local.svg" caption="A diagram showing local data storage running on the compute nodes" alt="A diagram showing local data storage running on the compute nodes" >}} + +On the other hand, hyper-converged systems are often implemented using local storage (when you do +not need replication) and with software-defined storages, often installed directly in Kubernetes, +such as [Rook/Ceph](https://rook.io/), [OpenEBS](https://openebs.io/), +[Longhorn](https://longhorn.io/), [LINSTOR](https://linbit.com/linstor/), and others. + +{{< figure src="storage-clustered.svg" caption="A diagram showing clustered data storage running on the compute nodes" alt="A diagram showing clustered data storage running on the compute nodes" >}} + +A hyper-converged system has its advantages. For example, data locality: when your data is stored +locally, access to such data is faster. But there are disadvantages as such a system is usually +more difficult to manage and maintain. + +At Ænix, we wanted to provide a ready-to-use solution that could be used without the need to +purchase and setup an additional external storage, and that was optimal in terms of speed and +resource utilization. LINSTOR became that solution. +The time-tested and industry-popular technologies such as LVM and ZFS as backend gives confidence +that data is securely stored. DRBD-based replication is incredible fast and consumes a small amount +of computing resources. + +For installing LINSTOR in Kubernetes, there is the Piraeus project, which already provides a +ready-made block storage to use with KubeVirt. + +{{< note >}} +In case you are using Talos Linux, as we described in the +[previous article](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-1/), you will +need to enable the necessary kernel modules in advance, and configure piraeus as described in the +[instruction](https://github.com/piraeusdatastore/piraeus-operator/blob/v2/docs/how-to/talos.md). +{{< /note >}} + +## Networking for Kubernetes VMs + +Despite having the similar interface - CNI, The network architecture in Kubernetes is actually more +complex and typically consists of many independent components that are not directly connected to +each other. In fact, you can split Kubernetes networking into four layers, which are described below. + +### Node Network (Data Center Network) + +The network through which nodes are interconnected with each other. This network is usually not +managed by Kubernetes, but it is an important one because, without it, nothing would work. +In practice, the bare metal infrastructure usually has more than one of such networks e.g. +one for node-to-node communication, second for storage replication, third for external access, etc. + +{{< figure src="net-nodes.svg" caption="A diagram showing the role of the node network (data center network) on the Kubernetes networking scheme" alt="A diagram showing the role of the node network (data center network) on the Kubernetes networking scheme" >}} + +Configuring the physical network interaction between nodes goes beyond the scope of this article, +as in most situations, Kubernetes utilizes already existing network infrastructure. + +### Pod Network + +This is the network provided by your CNI plugin. The task of the CNI plugin is to ensure transparent +connectivity between all containers and nodes in the cluster. Most CNI plugins implement a flat +network from which separate blocks of IP addresses are allocated for use on each node. + +{{< figure src="net-pods.svg" caption="A diagram showing the role of the pod network (CNI-plugin) on the Kubernetes network scheme" alt="A diagram showing the role of the pod network (CNI-plugin) on the Kubernetes network scheme" >}} + +In practice, your cluster can have several CNI plugins managed by +[Multus](https://github.com/k8snetworkplumbingwg/multus-cni). This approach is often used in +virtualization solutions based on KubeVirt - [Rancher](https://www.rancher.com/) and +[OpenShift](https://www.redhat.com/en/technologies/cloud-computing/openshift/virtualization). +The primary CNI plugin is used for integration with Kubernetes services, while additional CNI +plugins are used to implement private networks (VPC) and integration with the physical networks +of your data center. + +The [default CNI-plugins](https://github.com/containernetworking/plugins/tree/main/plugins) can +be used to connect bridges or physical interfaces. Additionally, there are specialized plugins +such as [macvtap-cni](https://github.com/kubevirt/macvtap-cni) which are designed to provide +more performance. + +One additional aspect to keep in mind when running virtual machines in Kubernetes is the need for +IPAM (IP Address Management), especially for secondary interfaces provided by Multus. This is +commonly managed by a DHCP server operating within your infrastructure. Additionally, the allocation +of MAC addresses for virtual machines can be managed by +[Kubemacpool](https://github.com/k8snetworkplumbingwg/kubemacpool). + +Although in our platform, we decided to go another way and fully rely on +[Kube-OVN](https://www.kube-ovn.io/). This CNI plugin is based on OVN (Open Virtual Network) which +was originally developed for OpenStack and it provides a complete network solution for virtual +machines in Kubernetes, features Custom Resources for managing IPs and MAC addresses, supports +live migration with preserving IP addresses between the nodes, and enables the creation of VPCs +for physical network separation between tenants. + +In Kube-OVN you can assign separate subnets to an entire namespace or connect them as additional +network interfaces using Multus. + +### Services Network + +In addition to the CNI plugin, Kubernetes also has a services network, which is primarily needed +for service discovery. +Contrary to traditional virtual machines, Kubernetes is originally designed to run pods with a +random address. +And the services network provides a convenient abstraction (stable IP addresses and DNS names) +that will always direct traffic to the correct pod. +The same approach is also commonly used with virtual machines in clouds despite the fact that +their IPs are usually static. + +{{< figure src="net-services.svg" caption="A diagram showing the role of the services network (services network plugin) on the Kubernetes network scheme" alt="A diagram showing the role of the services network (services network plugin) on the Kubernetes network scheme" >}} + + +The implementation of the services network in Kubernetes is handled by the services network plugin, +The standard implementation is called **kube-proxy** and is used in most clusters. +But nowadays, this functionality might be provided as part of the CNI plugin. The most advanced +implementation is offered by the [Cilium](https://cilium.io/) project, which can be run in kube-proxy replacement mode. + +Cilium is based on the eBPF technology, which allows for efficient offloading of the Linux +networking stack, thereby improving performance and security compared to traditional methods based +on iptables. + +In practice, Cilium and Kube-OVN can be easily +[integrated](https://kube-ovn.readthedocs.io/zh-cn/stable/en/advance/with-cilium/) to provide a +unified solution that offers seamless, multi-tenant networking for virtual machines, as well as +advanced network policies and combined services network functionality. + +### External Traffic Load Balancer + +At this stage, you already have everything needed to run virtual machines in Kubernetes. +But there is actually one more thing. +You still need to access your services from outside your cluster, and an external load balancer +will help you with organizing this. + +For bare metal Kubernetes clusters, there are several load balancers available: +[MetalLB](https://metallb.universe.tf/), [kube-vip](https://kube-vip.io/), +[LoxiLB](https://www.loxilb.io/), also [Cilium](https://docs.cilium.io/en/latest/network/lb-ipam/) and +[Kube-OVN](https://kube-ovn.readthedocs.io/zh-cn/latest/en/guide/loadbalancer-service/) +provides built-in implementation. + +The role of a external load balancer is to provide a stable address available externally and direct +external traffic to the services network. +The services network plugin will direct it to your pods and virtual machines as usual. + +{{< figure src="net-loadbalancer.svg" caption="A diagram showing the role of the external load balancer on the Kubernetes network scheme" alt="The role of the external load balancer on the Kubernetes network scheme" >}} + +In most cases, setting up a load balancer on bare metal is achieved by creating floating IP address +on the nodes within the cluster, and announce it externally using ARP/NDP or BGP protocols. + +After exploring various options, we decided that MetalLB is the simplest and most reliable solution, +although we do not strictly enforce the use of only it. + +Another benefit is that in L2 mode, MetalLB speakers continuously check their neighbour's state by +sending preforming liveness checks using a memberlist protocol. +This enables failover that works independently of Kubernetes control-plane. + +## Conclusion + +This concludes our overview of virtualization, storage, and networking in Kubernetes. +The technologies mentioned here are available and already pre-configured on the +[Cozystack](https://github.com/aenix-io/cozystack) platform, where you can try them with no limitations. + +In the [next article](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-3/), +I'll detail how, on top of this, you can implement the provisioning of fully functional Kubernetes +clusters with just the click of a button. + +--- + +*Originally published at 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+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + diff --git a/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-3/index.md b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-3/index.md new file mode 100644 index 0000000..c00dbbe --- /dev/null +++ b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-3/index.md @@ -0,0 +1,271 @@ +--- +layout: blog +title: "DIY: Create Your Own Cloud with Kubernetes (Part 3)" +slug: diy-create-your-own-cloud-with-kubernetes-part-3 +date: 2024-04-05T07:40:00+00:00 +--- + +**Author**: Andrei Kvapil (Ænix) + +Approaching the most interesting phase, this article delves into running Kubernetes within +Kubernetes. Technologies such as Kamaji and Cluster API are highlighted, along with their +integration with KubeVirt. + +Previous discussions have covered +[preparing Kubernetes on bare metal](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-1/) +and +[how to turn Kubernetes into virtual machines management system](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-2). +This article concludes the series by explaining how, using all of the above, you can build a +full-fledged managed Kubernetes and run virtual Kubernetes clusters with just a click. + +First up, let's dive into the Cluster API. + +## Cluster API + +Cluster API is an extension for Kubernetes that allows the management of Kubernetes clusters as +custom resources within another Kubernetes cluster. + +The main goal of the Cluster API is to provide a unified interface for describing the basic +entities of a Kubernetes cluster and managing their lifecycle. This enables the automation of +processes for creating, updating, and deleting clusters, simplifying scaling, and infrastructure +management. + +Within the context of Cluster API, there are two terms: **management cluster** and +**tenant clusters**. + +- **Management cluster** is a Kubernetes cluster used to deploy and manage other clusters. +This cluster contains all the necessary Cluster API components and is responsible for describing, +creating, and updating tenant clusters. It is often used just for this purpose. +- **Tenant clusters** are the user clusters or clusters deployed using the Cluster API. They are +created by describing the relevant resources in the management cluster. They are then used for +deploying applications and services by end-users. + +It's important to understand that physically, tenant clusters do not necessarily have to run on +the same infrastructure with the management cluster; more often, they are running elsewhere. + +{{< figure src="clusterapi1.svg" caption="A diagram showing interaction of management Kubernetes cluster and tenant Kubernetes clusters using Cluster API" alt="A diagram showing interaction of management Kubernetes cluster and tenant Kubernetes clusters using Cluster API" >}} + +For its operation, Cluster API utilizes the concept of _providers_ which are separate controllers +responsible for specific components of the cluster being created. Within Cluster API, there are +several types of providers. The major ones are: + + - **Infrastructure Provider**, which is responsible for providing the computing infrastructure, such as virtual machines or physical servers. + - **Control Plane Provider**, which provides the Kubernetes control plane, namely the components kube-apiserver, kube-scheduler, and kube-controller-manager. + - **Bootstrap Provider**, which is used for generating cloud-init configuration for the virtual machines and servers being created. + +To get started, you will need to install the Cluster API itself and one provider of each type. +You can find a complete list of supported providers in the project's +[documentation](https://cluster-api.sigs.k8s.io/reference/providers.html). + +For installation, you can use the `clusterctl` utility, or +[Cluster API Operator](https://github.com/kubernetes-sigs/cluster-api-operator) +as the more declarative method. + +## Choosing providers + +### Infrastructure provider + +To run Kubernetes clusters using KubeVirt, the +[KubeVirt Infrastructure Provider](https://github.com/kubernetes-sigs/cluster-api-provider-kubevirt) +must be installed. +It enables the deployment of virtual machines for worker nodes in the same management cluster, where +the Cluster API operates. + +### Control plane provider + +The [Kamaji](https://github.com/clastix/kamaji) project offers a ready solution for running the +Kubernetes control plane for tenant clusters as containers within the management cluster. +This approach has several significant advantages: + +- **Cost-effectiveness**: Running the control plane in containers avoids the use of separate control +plane nodes for each cluster, thereby significantly reducing infrastructure costs. +- **Stability**: Simplifying architecture by eliminating complex multi-layered deployment schemes. +Instead of sequentially launching a virtual machine and then installing etcd and Kubernetes components +inside it, there's a simple control plane that is deployed and run as a regular application inside +Kubernetes and managed by an operator. +- **Security**: The cluster's control plane is hidden from the end user, reducing the possibility +of its components being compromised, and also eliminates user access to the cluster's certificate +store. This approach to organizing a control plane invisible to the user is often used by cloud providers. + +### Bootstrap provider + +[Kubeadm](https://github.com/kubernetes-sigs/cluster-api/tree/main/bootstrap) as the Bootstrap +Provider - as the standard method for preparing clusters in Cluster API. This provider is developed +as part of the Cluster API itself. It requires only a prepared system image with kubelet and kubeadm +installed and allows generating configs in the cloud-init and ignition formats. + +It's worth noting that Talos Linux also supports provisioning via the Cluster API and +[has](https://github.com/siderolabs/cluster-api-bootstrap-provider-talos) +[providers](https://github.com/siderolabs/cluster-api-bootstrap-provider-talos) for this. +Although [previous articles](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-1/) +discussed using Talos Linux to set up a management cluster on bare-metal nodes, to provision tenant +clusters the Kamaji+Kubeadm approach has more advantages. +It facilitates the deployment of Kubernetes control planes in containers, thus removing the need for +separate virtual machines for control plane instances. This simplifies the management and reduces costs. + +## How it works + +The primary object in Cluster API is the Cluster resource, which acts as the parent for all the others. +Typically, this resource references two others: a resource describing the **control plane** and a +resource describing the **infrastructure**, each managed by a separate provider. + +Unlike the Cluster, these two resources are not standardized, and their kind depends on the specific +provider you are using: + +{{< figure src="clusterapi2.svg" caption="A diagram showing the relationship of a Cluster resource and the resources it links to in Cluster API" alt="A diagram showing the relationship of a Cluster resource and the resources it links to in Cluster API" >}} + +Within Cluster API, there is also a resource named MachineDeployment, which describes a group of nodes, +whether they are physical servers or virtual machines. This resource functions similarly to standard +Kubernetes resources such as Deployment, ReplicaSet, and Pod, providing a mechanism for the +declarative description of a group of nodes and automatic scaling. + +In other words, the MachineDeployment resource allows you to declaratively describe nodes for your +cluster, automating their creation, deletion, and updating according to specified parameters and +the requested number of replicas. + +{{< figure src="machinedeploymentres.svg" caption="A diagram showing the relationship of a MachineDeployment resource and its children in Cluster API" alt="A diagram showing the relationship of a Cluster resource and its children in Cluster API" >}} + +To create machines, MachineDeployment refers to a template for generating the machine itself and a +template for generating its cloud-init config: + +{{< figure src="clusterapi3.svg" caption="A diagram showing the relationship of a MachineDeployment resource and the resources it links to in Cluster API" alt="A diagram showing the relationship of a Cluster resource and the resources it links to in Cluster API" >}} + +To deploy a new Kubernetes cluster using Cluster API, you will need to prepare the following set of resources: + +- A general Cluster resource +- A KamajiControlPlane resource, responsible for the control plane operated by Kamaji +- A KubevirtCluster resource, describing the cluster configuration in KubeVirt +- A KubevirtMachineTemplate resource, responsible for the virtual machine template +- A KubeadmConfigTemplate resource, responsible for generating tokens and cloud-init +- At least one MachineDeployment to create some workers + +## Polishing the cluster + +In most cases, this is sufficient, but depending on the providers used, you may need other resources +as well. You can find examples of the resources created for each type of provider in the +[Kamaji project documentation](https://github.com/clastix/cluster-api-control-plane-provider-kamaji?tab=readme-ov-file#-supported-capi-infrastructure-providers). + +At this stage, you already have a ready tenant Kubernetes cluster, but so far, it contains nothing +but API workers and a few core plugins that are standardly included in the installation of any +Kubernetes cluster: **kube-proxy** and **CoreDNS**. For full integration, you will need to install +several more components: + +To install additional components, you can use a separate +[Cluster API Add-on Provider for Helm](https://github.com/kubernetes-sigs/cluster-api-addon-provider-helm), +or the same [FluxCD](https://fluxcd.io/) discussed in +[previous articles](/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-1/). + +When creating resources in FluxCD, it's possible to specify the target cluster by referring to the +kubeconfig generated by Cluster API. Then, the installation will be performed directly into it. +Thus, FluxCD becomes a universal tool for managing resources both in the management cluster and +in the user tenant clusters. + +{{< figure src="fluxcd.svg" caption="A diagram showing the interaction scheme of fluxcd, which can install components in both management and tenant Kubernetes clusters" alt="A diagram showing the interaction scheme of fluxcd, which can install components in both management and tenant Kubernetes clusters" >}} + +What components are being discussed here? Generally, the set includes the following: + +### CNI Plugin + +To ensure communication between pods in a tenant Kubernetes cluster, it's necessary to deploy a +CNI plugin. This plugin creates a virtual network that allows pods to interact with each other +and is traditionally deployed as a Daemonset on the cluster's worker nodes. You can choose and +install any CNI plugin that you find suitable. + +{{< figure src="components1.svg" caption="A diagram showing a CNI plugin installed inside the tenant Kubernetes cluster on a scheme of nested Kubernetes clusters" alt="A diagram showing a CNI plugin installed inside the tenant Kubernetes cluster on a scheme of nested Kubernetes clusters" >}} + +### Cloud Controller Manager + +The main task of the Cloud Controller Manager (CCM) is to integrate Kubernetes with the cloud +infrastructure provider's environment (in your case, it is the management Kubernetes cluster +in which all worksers of tenant Kubernetes are provisioned). Here are some tasks it performs: + +1. When a service of type LoadBalancer is created, the CCM initiates the process of creating a cloud load balancer, which directs traffic to your Kubernetes cluster. +1. If a node is removed from the cloud infrastructure, the CCM ensures its removal from your cluster as well, maintaining the cluster's current state. +1. When using the CCM, nodes are added to the cluster with a special taint, `node.cloudprovider.kubernetes.io/uninitialized`, + which allows for the processing of additional business logic if necessary. After successful initialization, this taint is removed from the node. + +Depending on the cloud provider, the CCM can operate both inside and outside the tenant cluster. + +[The KubeVirt Cloud Provider](https://github.com/kubevirt/cloud-provider-kubevirt) is designed +to be installed in the external parent management cluster. Thus, creating services of type +LoadBalancer in the tenant cluster initiates the creation of LoadBalancer services in the parent +cluster, which direct traffic into the tenant cluster. + +{{< figure src="components2.svg" caption="A diagram showing a Cloud Controller Manager installed outside of a tenant Kubernetes cluster on a scheme of nested Kubernetes clusters and the mapping of services it manages from the parent to the child Kubernetes cluster" alt="A diagram showing a Cloud Controller Manager installed outside of a tenant Kubernetes cluster on a scheme of nested Kubernetes clusters and the mapping of services it manages from the parent to the child Kubernetes cluster" >}} + +### CSI Driver + +The Container Storage Interface (CSI) is divided into two main parts for interacting with storage +in Kubernetes: + +- **csi-controller**: This component is responsible for interacting with the cloud provider's API +to create, delete, attach, detach, and resize volumes. +- **csi-node**: This component runs on each node and facilitates the mounting of volumes to pods +as requested by kubelet. + +In the context of using the [KubeVirt CSI Driver](https://github.com/kubevirt/csi-driver), a unique +opportunity arises. Since virtual machines in KubeVirt runs within the management Kubernetes cluster, +where a full-fledged Kubernetes API is available, this opens the path for running the csi-controller +outside of the user's tenant cluster. This approach is popular in the KubeVirt community and offers +several key advantages: + +- **Security**: This method hides the internal cloud API from the end-user, providing access to +resources exclusively through the Kubernetes interface. Thus, it reduces the risk of direct access +to the management cluster from user clusters. +- **Simplicity and Convenience**: Users don't need to manage additional controllers in their clusters, +simplifying the architecture and reducing the management burden. + +However, the CSI-node must necessarily run inside the tenant cluster, as it directly interacts with +kubelet on each node. This component is responsible for the mounting and unmounting of volumes into pods, +requiring close integration with processes occurring directly on the cluster nodes. + +The KubeVirt CSI Driver acts as a proxy for ordering volumes. When a PVC is created inside the tenant +cluster, a PVC is created in the management cluster, and then the created PV is connected to the +virtual machine. + +{{< figure src="components3.svg" caption="A diagram showing a CSI plugin components installed on both inside and outside of a tenant Kubernetes cluster on a scheme of nested Kubernetes clusters and the mapping of persistent volumes it manages from the parent to the child Kubernetes cluster" alt="A diagram showing a CSI plugin components installed on both inside and outside of a tenant Kubernetes cluster on a scheme of nested Kubernetes clusters and the mapping of persistent volumes it manages from the parent to the child Kubernetes cluster" >}} + +### Cluster Autoscaler + +The [Cluster Autoscaler](https://github.com/kubernetes/autoscaler) is a versatile component that +can work with various cloud APIs, and its integration with Cluster-API is just one of the available +functions. For proper configuration, it requires access to two clusters: the tenant cluster, to +track pods and determine the need for adding new nodes, and the managing Kubernetes cluster +(management kubernetes cluster), where it interacts with the MachineDeployment resource and adjusts +the number of replicas. + +Although Cluster Autoscaler usually runs inside the tenant Kubernetes cluster, in this situation, +it is suggested to install it outside for the same reasons described before. This approach is +simpler to maintain and more secure as it prevents users of tenant clusters from accessing the +management API of the management cluster. + +{{< figure src="components4.svg" caption="A diagram showing a Cluster Autoscaler installed outside of a tenant Kubernetes cluster on a scheme of nested Kubernetes clusters" alt="A diagram showing a Cloud Controller Manager installed outside of a tenant Kubernetes cluster on a scheme of nested Kubernetes clusters" >}} + +### Konnectivity + +There's another additional component I'd like to mention - +[Konnectivity](https://kubernetes.io/docs/tasks/extend-kubernetes/setup-konnectivity/). +You will likely need it later on to get webhooks and the API aggregation layer working in your +tenant Kubernetes cluster. This topic is covered in detail in one of my +[previous article](https://kubernetes.io/blog/2021/12/22/kubernetes-in-kubernetes-and-pxe-bootable-server-farm/#webhooks-and-api-aggregation-layer). + +Unlike the components presented above, Kamaji allows you to easily enable Konnectivity and manage +it as one of the core components of your tenant cluster, alongside kube-proxy and CoreDNS. + +## Conclusion + +Now you have a fully functional Kubernetes cluster with the capability for dynamic scaling, automatic +provisioning of volumes, and load balancers. + +Going forward, you might consider metrics and logs collection from your tenant clusters, but that +goes beyond the scope of this article. + +Of course, all the components necessary for deploying a Kubernetes cluster can be packaged into a +single Helm chart and deployed as a unified application. This is precisely how we organize the +deployment of managed Kubernetes clusters with the click of a button on our open PaaS platform, +[Cozystack](https://cozystack.io/), where you can try all the technologies described in the article +for free. + +--- + +*Originally published at [https://kubernetes.io](https://kubernetes.io/blog/2024/04/05/diy-create-your-own-cloud-with-kubernetes-part-3/) on April 5, 2024.* diff --git a/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-3/machinedeploymentres.svg b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-3/machinedeploymentres.svg new file mode 100644 index 0000000..8adeee6 --- /dev/null +++ b/content/en/blog/2024-04-05-diy-create-your-own-cloud-with-kubernetes-part-3/machinedeploymentres.svg @@ -0,0 +1,25 @@ + + + + + + + + + + + + + + + + + + + + + + + + +