Migrating Helm-based Legacy Projects

Migrating Helm-based Legacy Projects

Instructions for migrating a legacy Helm-based project to use the new Kubebuilder-style layout.

Overview

The motivations for the new layout are related to bringing more flexibility to users and part of the process to Integrating Kubebuilder and Operator SDK.

What was changed

The deploy directory was replaced with the config directory including a new layout of Kubernetes manifests files:
- CRD manifests in deploy/crds/ are now in config/crd/bases
- CR manifests in deploy/crds/ are now in config/samples
- Controller manifest deploy/operator.yaml is now in config/manager/manager.yaml
- RBAC manifests in deploy are now in config/rbac/
build/Dockerfile is moved to Dockerfile in the project root directory

What is new

Projects are now scaffold using:

kustomize to manage Kubernetes resources needed to deploy your operator
A Makefile with helpful targets for build, test, and deployment, and to give you flexibility to tailor things to your project’s needs
Updated metrics configuration using kube-auth-proxy, a --metrics-addr flag, and kustomize-based deployment of a Kubernetes Service and prometheus operator ServiceMonitor

How to migrate

The easy migration path is to create a new project from the scratch and let the tool scaffold the files properly and then, just replace with your customizations and implementations. Following an example.

Creating a new project

In Kubebuilder-style projects, CRD groups are defined using two different flags (--group and --domain).

When we initialize a new project, we need to specify the domain that all APIs in our project will share, so before creating the new project, we need to determine which domain we’re using for the APIs in our existing project.

To determine the domain, look at the spec.group field in your CRDs in the deploy/crds directory.

The domain is everything after the first DNS segment. Using cache.example.com as an example, the --domain would be example.com.

So let’s create a new project with the same domain (example.com):

mkdir nginx-operator
cd nginx-operator
operator-sdk init --plugins=helm --domain=example.com

Now that we have our new project initialized, we need to re-create each of our APIs. Using our API example from earlier (cache.example.com), we’ll use cache for the --group flag.

For --version and --kind, we use spec.versions[0].name and spec.names.kind, respectively.

For each API in the existing project, run:

operator-sdk create api \
    --group=cache \
    --version=<version> \
    --kind=<Kind> \
    --helm-chart=<path_to_existing_project>/helm-charts/<chart>

Migrating your Custom Resource samples

Update the CR manifests in config/samples with the values of the CRs in your existing project which are in deploy/crds/<group>_<version>_<kind>_cr.yaml

Migrating `watches.yaml`

Check if you have custom options in the watches.yaml file of your existing project. If so, update the new watches.yaml file to match. In our example, it will look like:

# Use the 'create api' subcommand to add watches to this file.
- group: example.com
  version: v1alpha1
  kind: Nginx
  chart: helm-charts/nginx
# +kubebuilder:scaffold:watch

NOTE: Do not remove the +kubebuilder:scaffold:watch marker. It allows the tool to update the watches file when new APIs are created.

Checking the Permissions (RBAC)

In your new project, roles are automatically generated in config/rbac/role.yaml. If you modified these permissions manually in deploy/role.yaml in your existing project, you need to re-apply them in config/rbac/role.yaml.

New projects are configured to watch all namespaces by default, so they need a ClusterRole to have the necessary permissions. Ensure that config/rbac/role.yaml remains a ClusterRole if you want to retain the default behavior of the new project conventions. For further information refer to the [operator scope][operator-scope] documentation.

The following rules were used in earlier versions of helm-operator to automatically create and manage services and servicemonitors for metrics collection. If your operator’s charts don’t require these rules, they can safely be left out of the new config/rbac/role.yaml file:

  - apiGroups:
    - monitoring.coreos.com
    resources:
    - servicemonitors
    verbs:
    - get
    - create
  - apiGroups:
    - apps
    resourceNames:
    - memcached-operator
    resources:
    - deployments/finalizers
    verbs:
    - update

Configuring your Operator

If your existing project has customizations in deploy/operator.yaml, they need to be ported to config/manager/manager.yaml. If you are passing custom arguments in your deployment, make sure to also update config/default/auth_proxy_patch.yaml.

Note that the following environment variables are no longer used.

OPERATOR_NAME is deprecated. It is used to define the name for a leader election config map. Operator authors should begin using --leader-election-id instead.
POD_NAME was used to enable a particular pod to hold the leader election lock when the Helm operator used the leader for life mechanism. Helm operator now uses controller-runtime’s leader with lease mechanism, and POD_NAME is no longer necessary.

Exporting metrics

If you are using metrics and would like to keep them exported you will need to configure it in the config/default/kustomization.yaml. Please see the metrics doc to know how you can perform this setup.

The default port used by the metric endpoint binds to was changed from :8383 to :8080. To continue using port 8383, specify --metrics-addr=:8383 when you start the operator.