Multi-Tenancy in Kubernetes using Loft’s Vcluster

 

Consider a typical case of a virtual machine(a.k.a VM). A VM is a machine that is running inside a machine and is used widely for development purposes. VMs are so popular because several people can have their own “machines” that are completely separated from one another, allowing them to work separately, but also use the same pool of shared resources. So a team could have a machine that runs non-stop builds, while other teams could have individual machines that they do development work on. The machines can shut down, startup, receive updates, and have software installed, all of this independently of each other. Now, consider the same use case, but for clusters.

In a large organization, you would generally have several teams that use various clusters for different stages of development. The biggest problem here is that each team will need a different cluster, meaning that each team would end up managing its own Kubernetes cluster. This is inefficient and costly since there is a lot of repetition when creating and maintaining clusters, and there are a lot of costs involved as well. The common solution that organizations employ here is to create a single cluster that is maintained by dedicated DevOps teams. The cluster is then broken down into many different isolated namespaces and assigned to different teams.

However, there are several problems with this approach. The main problem is access restriction. Large organizations generally deal with sensitive data that only certain individuals should have access to. Not complying with these data protection rules can cost the company millions. But when everything is in a shared cluster, the problem of restricting access to various teams or persons within the team comes up. Even giving access to people in a team can be a hassle. The next problem with a shared cluster is that it also shares resources. This could mean that a handful of the teams could use the majority of cluster resources while other teams don’t have the required computational power to run their application. In a dev environment, people can expect code to break the system frequently, while in a prod environment, nothing should ideally go wrong. These are two extremes that the cluster might not be able to handle, since the resources of various teams can get mixed up.

Now that we’ve listed out the problems, and you can see the title of this section, I think you should be able to figure out the solution: virtual clusters.

How do virtual clusters work?

To observe how virtual clusters work, we will be taking Loft into consideration. Similar to how one would manually do it, Loft creates a namespace within the cluster. However, Loft also then deploys a lightweight Kubernetes cluster to the namespace based on k3s, which is a lightweight implementation of k8s. This cluster contained within the namespace will now have a fully featured API server + controller, meaning that it is essentially a cluster of its own. Every time a new cluster is deployed into a namespace, a new virtual cluster is created, and each team or individual can be assigned their own separate cluster. The most interesting part is that you don’t have to keep a separate DevOps team to create and destroy the clusters, since Loft allows developers to easily do this themselves. However, it is likely that in large organizations, a team will be there to monitor and handle resource usage, and you will need DevOps engineers to initially set up Loft in your company cluster.

Setting up Loft in your existing cluster isn’t particularly difficult. If you have multiple clusters hosted in various cloud service providers, you only have to install Loft on one of those clusters. You can then network the other clusters to it and create a larger self-service cluster. The next step is to handle access by creating users that have various permissions. This is something we couldn’t do previously when using only namespaces to segregate the clusters. Once that is done, developers can create their own clusters to suit their needs.

Getting Started

Before we start the Loft lab, you need to have a Kubernetes cluster up and running. If you already have a cluster available, that can be used. If not, you can get Minikube. Minikube starts up a single node cluster in your local machine, which is fine since the whole idea of Loft is to use a single cluster that then builds multiple virtual clusters on top of it. If you were to have additional nodes, Loft would still be able to create clusters that shared resources between the nodes. To start, install the Loft CLI:

curl -s -L "https://github.com/loft-sh/loft/releases/latest" | sed -nE 's!.*"([^"]*loft-linux-amd64)".*!https://github.com\1!p' | xargs -n 1 curl -L -o loft && chmod +x loft;
sudo mv loft /usr/local/bin;

If you are on Windows:

md -Force "$Env:APPDATA\loft"; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]'Tls,Tls11,Tls12';
Invoke-WebRequest -UseBasicParsing ((Invoke-WebRequest -URI "https://github.com/loft-sh/loft/releases/latest" -UseBasicParsing).Content -replace "(?ms).*`"([^`"]*loft-windows-amd64.exe)`".*","https://github.com/`$1") -o $Env:APPDATA\loft\loft.exe;
$env:Path += ";" + $Env:APPDATA + "\loft";
[Environment]::SetEnvironmentVariable("Path", $env:Path, [System.EnvironmentVariableTarget]::User);

Then test if Loft has properly been installed:

loft --version

Make sure you are using the correct Kubeconfig file, and then deploy loft to your k8s cluster using your newly installed Loft CLI:

loft start

Once the above command finishes running, you should see the login details printed out. The username, password, access URL, and command to log in via CLI can be seen here. For now, head over to the localhost URL provided in the output using your browser, and use the login details to log into Loft. Once you’re inside, you will see several tabs to the left which show the various sections of the UI. The cluster section shows the clusters you have connected to Loft. If you are running a single node cluster with Minikube, then only that cluster will show since it is already connected to Loft. From this point, you can use the “Connect cluster” button to connect any other clusters you have.

Connecting a cluster is a simple 4-step process, although you only actually have to provide the kubeconfig file of the cluster that you are connecting to. Loft uses Kiosk which handles everything from that point. You can go back to your clusters page and see that the new remote cluster has been added. Loft also installs Kiosk on the remote cluster so that it gets managed as well. You also have a list of Helm charts that you can 1-click install on your remote clusters, such as dashboards or certificate managers.

Now that the clusters are created, it’s time to add users. The users’ section of the page should give you a form that you can use to add users, as well as bind cluster roles to the user so that they can have restricted/unrestricted access to the cluster. Once the user has been created, you get a link that you can provide to the user, so that they can start accessing the cluster. You can now log out of Loft and then use the URL you were just provided to log back in as that user. You would no longer have access to the admin parts of Loft since this is a non-admin user, but you should be able to see and use all the clusters + remote clusters.

Now, as a non-admin user, you should be able to start creating virtual clusters. Head over to the vClusters section and select “Create virtual cluster”. All you have to do to get a cluster up and running is to type in a name for your virtual cluster. No additional configuration, no creating namespaces, just a one-step process that will get your cluster up and running in under a minute. This means that any ordinary developer (or non-developer) can now start their own clusters and start developing without any interference from external teams. Of course, just because you don’t have to do it doesn’t mean nothing happens in the background. If you were to check the namespaces in the cluster (kubectl get ns) you would notice that a new namespace has been created, which is where the virtual cluster now resides.

This namespace also has two pods running within it used to maintain a lightweight Kubernetes cluster on it. Before you log into the virtual cluster, you need to log into Loft via the CLI. To do this, run the loft login command:

loft login https://my-loft.com --username myuser --access-key myaccesskey

The access-key is something you have to create. Go to the profile section of Loft, where you should be able to find an Access Keys tab where you can generate a new access key. Use the access key with the above command and with that, you are ready to log into your vCluster. If you get an error about logging in to an unsecured endpoint, use the --insecure flag within the command to log in.

To log into this virtual cluster, use the loft CLI. To do this, choose the connect option that can be found in the loft UI, vClusters section which should bring up a command. This command will configure your Kube context to start working inside the Loft vCluster. If you get the cluster info using kubectl cluster-info, you will see that the master node is pointing to the Loft URL. You now have a fully configured Loft virtual cluster that runs on top of your main cluster.

To finish, let’s talk about Loft’s sleep state. If you are not actively using a vCluster, you can either use the UI or have the cluster automatically go to sleep. This frees up cluster resources so that a different vCluster can use them. Alternatively, if you have multiple clusters that are providing for your main cluster, those cluster resources can be deallocated, saving you money. The main thing to note here is that you sleep the vCluster, not remove it, meaning that if you were to use the CLI and try to log in to the cluster again, it will automatically start up and allow you to start working with the cluster.

vCluster Docker Extension

Now you can manage your vclusters running on Docker Desktop too. This new Docker Extension helps you to create fully functional virtual Kubernetes clusters. Each vcluster runs inside a namespace of the underlying k8s cluster. It’s cheaper than creating separate full-blown clusters and it offers better multi-tenancy and isolation than regular namespaces.

 

Why Virtual Kubernetes Clusters?


– Cluster Scoped Resources: much more powerful than simple namespaces (virtual clusters allow users to use CRDs, namespaces, cluster roles etc.)
– Ease of Use: usable in any Kubernetes cluster and created in seconds either via a single command or cluster-api
– Cost Efficient: much cheaper and efficient than real clusters (single pod and shared resources just like for namespaces)
– Lightweight: built upon the ultra-fast k3s distribution with minimal overhead per virtual cluster (other distributions work as well)
– Strict isolation: complete separate Kubernetes control plane and access point for each vcluster while still being able to share certain services of the underlying host cluster
– Cluster Wide Permissions: allow users to install apps which require cluster-wide permissions while being limited to actually just one namespace within the host cluster
– Great for Testing: allow you to test different Kubernetes versions inside a single host cluster which may have a different version than the virtual clusters

Thanks to Collabnix community member Mewantha Bandar  , a Senior Software Engineer at IFS for contributing this content for KubeLabs – The #1 Kubernetes Resources for all Levels. Do you have anything exciting to share with Collabnix community? Do visit Collabnix community Slack and we might feature you in Collabnix website.

References

 

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