Learning Center operator

Before deploying workshops, install a Kubernetes operator for Learning Center. The operator manages the setup of the environment for each workshop and deploys instances of a workshop for each person.

For basic information about installing the operator, see Install Learning Center.

Installing and setting up Learning Center operator

The following is additional information about installing and setting up the Learning Center operator.

The Learning Center operator can be deployed to any Kubernetes cluster supporting custom resource definitions and the concept of operators. The cluster must have an ingress router configured, though only a basic deployment of the ingress controller is usually required. You do not need to configure the ingress controller to handle cluster wide edge termination of secure HTTP connections. Learning Center creates Kubernetes Ingress resources and supplies any secret for use with secure HTTP connections for each ingress.

For the ingress controller, VMware recommends the use of Contour over alternatives such as nginx. An nginx-based ingress controller has a less than optimal design. Every time a new ingress is created or deleted, the nginx config is reloaded. This causes websocket connections to terminate after a period of time. Learning Center terminals reconnect automatically in the case of the websocket connection being lost. However, not all applications you might use with specific workshops can handle loss of websocket connections so gracefully, and they might be impacted due to the use of an nginx ingress controller. This problem is not specific to Learning Center. It can impact any application when an nginx ingress controller is used frequently and ingresses are created or deleted frequently.

You can use a hosted Kubernetes solution from an IaaS provider such as Google, AWS, or Azure. If you do, as needed, increase any HTTP request timeout specified on the inbound load balancer for the ingress controller so that long-lived websocket connections can be used. In some cases, load balancers of hosted Kubernetes solutions only have a 30-second timeout. If possible, configure the timeout applying to websockets to be 1 hour.

If you deploy the web-based training portal, the cluster must have available persistent volumes of type ReadWriteOnce (RWO). A default storage class should have been defined so that persistent volume claims do not need to specify a storage class. For some Kubernetes distributions, including from IBM, it is necessary to configure Learning Center as to what user and group must be used for persistent volumes. If no default storage class is specified, or a specified storage class is required, you can configure Learning Center with the name of the storage class.

To install the Learning Center operator, you must have cluster admin access.

Cluster pod security policies

The Learning Center operator defines pod security policies to limit what users can do from workshops when deploying workloads to the cluster. The default policy prohibits running of images as the root user or using a privileged pod. Specified workshops can relax these restrictions and apply a policy that enables additional privileges required by the workshop.

VMware recommends that the pod security policy admission controller be enabled for the cluster to ensure that the pod security policies are applied. If the admission controller is not enabled, users can deploy workloads that run as the root user in a container, or run privileged pods.

If you are unable to enable the pod security policy admission controller, you should only provide access to workshops deployed using the Learning Center operator to users you trust.

Whether the absence of the pod security policy admission controller causes issues with access to persistent volumes depends on the cluster. Although minikube does not enable the pod security policy admission controller, it works as persistent volumes when mounted to give write permissions to all users.

No matter whether pod security policies are enabled, individual workshops must be reviewed as to what added privileges they grant before allowing their use in a cluster.

Specifying the ingress domain

When deploying instances of workshop environments, the operator must expose the instances by using an external URL for access to define the domain name that is used as a suffix to host names for instances.

Note: For the custom domain you are using, configure your DNS with a wildcard domain to forward all requests for subdomains of the custom domain to the ingress router of the Kubernetes cluster.

Note: For the custom domain you are using, DNS must have been configured with a wildcard domain to forward all requests for subdomains of the custom domain to the ingress router of the Kubernetes cluster.

VMware recommends that you avoid using a .dev domain name because such domain names require using HTTPS and not HTTP. Although you can provide a certificate for secure connections under the domain name for use by Learning Center, this doesn’t extend to what a workshop may do. If workshop instructions require that you create ingresses in Kubernetes using HTTP only, a .dev domain name cannot work.

Note: If you are running Kubernetes on your local machine using a system such as minikube and you don’t have a custom domain name that maps to the IP address for the cluster, you can use a nip.io address. For example, if minikube ip returned 192.168.64.1, you can use the 192.168.64.1.nip.io domain. You cannot use an address of form 127.0.0.1.nip.io, or subdomain.localhost. This causes a failure as internal services needing to connect to each other end up connecting to themselves instead, because the address resolves to the host loopback address of 127.0.0.1.

ingressDomain: learningcenter.my-domain.com

Set the environment variable manually

Set the INGRESS_DOMAIN environment variable on the operator deployment. To set the INGRESS_DOMAIN environment variable, run:

kubectl set env deployment/learningcenter-operator -n learningcenter INGRESS_DOMAIN=test

Where test is the domain name for your Kubernetes cluster.

Or if using a nip.io address:

kubectl set env deployment/learningcenter-operator -n learningcenter INGRESS_DOMAIN=192.168.64.1.nip.io

Use of environment variables to configure the operator is a shortcut for a simple use. VMware recommends using Tanzu CLI, or for more complicated scenarios, you can use the SystemProfile custom resource.

Enforcing secure connections

By default, the workshop portal and workshop sessions are accessible over HTTP connections. To use secure HTTPS connections, you must have access to a wildcard SSL certificate for the domain under which you want to host the workshops. You cannot use a self-signed certificate.

You can create Wildcard certificates by using letsencrypt <https://letsencrypt.org/>. After you have the certificate, you can define it as follows.

Configuration YAML

The easiest way to define the certificate is with the configuration passed to Tanzu CLI. So define the certificate and privateKey properties under the ingressSecret property to specify the certificate on the configuration YAML passed to Tanzu CLI:

ingressSecret:
  certificate: |
    -----BEGIN CERTIFICATE-----
    MIIFLTCCBBWgAwIBAgaSAys/V2NCTG9uXa9aAiYt7WJ3MA0GCSqGaIb3DQEBCwUA
                                    ...
    dHa6Ly9yMy5vamxlbmNyLm9yZzAiBggrBgEFBQawAoYWaHR0cDoaL3IzLmkubGVu
    -----END CERTIFICATE-----
  privateKey: |
    -----BEGIN PRIVATE KEY-----
    MIIEvQIBADAaBgkqhkiG9waBAQEFAASCBKcwggSjAgEAAoIBAaCx4nyc2xwaVOzf
                                    ...
    IY/9SatMcJZivH3F1a7SXL98PawPIOSR7986P7rLFHzNjaQQ0DWTaXBRt+oUDxpN
    -----END PRIVATE KEY-----

If you already have a TLS secret, follow these steps before deploying any workshops:

  1. Create the learningcenter namespace manually or the one you defined.
  2. Copy the TLS secret to the learningcenter namespace or to the one you defined, and use the secretName property as in this example:

    ingressSecret:
      secretName: workshops.example.com-tls
    

Create the TLS secret manually

To add the certificate as a secret in the learningcenter namespace or in the one you defined, the secret must be of type tls. You can create it using the kubectl create secret tls command:

kubectl create secret tls -n learningcenter workshops.example.com-tls --cert=workshops.example.com/fullchain.pem --key=workshops.example.com/privkey.pem

Having created the secret, if it is the secret corresponding to the default ingress domain you specified earlier, set the INGRESS_SECRET environment variable. This way you won’t use the configuration passed to Tanzu CLI on the operator deployment. This ensures the secret is applied automatically to any ingress created:

kubectl set env deployment/learningcenter-operator -n learningcenter INGRESS_SECRET=workshops.example.com-tls

If the certificate isn’t that of the default ingress domain, you can supply the domain name and name of the secret when creating a workshop environment or training portal. In either case, you must create secrets for the wildcard certificates in the learningcenter namespace or the one that you defined.

Specifying the ingress class

Any ingress routes created use the default ingress class. If you have multiple ingress class types available, and you must override which is used, you can define the ingressClass property on the configuration YAML as follows.

Configuration YAML

Define the ingressClass property on the configuration YAML passed to Tanzu CLI:

ingressClass: contour

Set the environment variable manually

Set the INGRESS_CLASS environment variable for the learningcenter operator:

kubectl set env deployment/learningcenter-operator -n learningcenter INGRESS_CLASS=contour

This applies only to the ingress created for the training portal and workshop sessions. It does not apply to the any ingress created from a workshop as part of the workshop instructions.

This can be necessary when a specific ingress provider is not reliable in maintaining websocket connections. For example, in the case of the nginx ingress controller when there are frequent creation or deletions of ingresses occurring in the cluster. See the earlier section, Installing and setting up Learning Center operator.

Trusting unsecured registries

One of the options available for workshops is to automatically deploy a container image registry each workshop session. When the Learning Center operator is configured to use a secure ingress with valid wildcard certificate, the image registry works out of the box.

If the Learning Center operator is not set up to use secure ingress, the image registry is accessed over HTTP and is regarded as not secure.

When using the optional support for building container images using docker, the docker daemon deployed for the workshop session is configured for the image registry being not secure yet pushing images to the image registry still works.

In this case of an image registry that is not secure, deploying images from the image registry to the Kubernetes cluster does not work unless the Kubernetes cluster is configured to trust the registry that is not secure.

How you configure a Kubernetes cluster to trust an unsecured registry varies based on how the Kubernetes cluster is deployed and what container runtime it uses.

If you are using minikube with dockerd, to ensure that the registry is trusted, you must set up the trust the first time you create the minikube instance.

To do this, first determine which IP subnet minikube uses for the inbound ingress router of the cluster. If you already have a minikube instance running, you can determine this by running minikube ip. If, for example, this reported 192.168.64.1, the subnet used is 129.168.64.0/24.

With this information, when you create a fresh minikube instance, you must supply the --insecure-registry option with the subnet:

minikube start --insecure-registry="129.168.64.0/24"

This option tells dockerd to regard as not secure any image registry deployed in the Kubernetes cluster and accessed through a URL exposed using an ingress route of the cluster itself.

Currently, there is no way to configure containerd to treat as not secure image registries that match a wildcard subdomain or reside in a subnet. It is therefore not possible to run workshops that must deploy images from the per session image registry when using containerd as the underlying Kubernetes cluster container runtime. This is a limitation of containerd, and there are no known plans for containerd to support this ability. This limits your ability to use Kubernetes clusters deployed with a tool such as kind, which relies on using containerd.

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