Developing Cluster API with Tilt

Overview

This document describes how to use kind and Tilt for a simplified workflow that offers easy deployments and rapid iterative builds.

Prerequisites

  1. Docker: v19.03 or newer
  2. kind: v0.17 or newer
  3. Tilt: v0.22.2 or newer
  4. kustomize: provided via make kustomize
  5. envsubst: provided via make envsubst
  6. helm: v3.7.1 or newer
  7. Clone the Cluster API repository locally
  8. Clone the provider(s) you want to deploy locally as well

Getting started

Create a kind cluster

A script to create a KIND cluster along with a local docker registry and the correct mounts to run CAPD is included in the hack/ folder.

To create a pre-configured cluster run:

./hack/kind-install-for-capd.sh

You can see the status of the cluster with:

kubectl cluster-info --context kind-capi-test

Create a tilt-settings file

Next, create a tilt-settings.yaml file and place it in your local copy of cluster-api. Here is an example:

default_registry: gcr.io/your-project-name-here
provider_repos:
- ../cluster-api-provider-aws
enable_providers:
- aws
- docker
- kubeadm-bootstrap
- kubeadm-control-plane

tilt-settings fields

allowed_contexts (Array, default=[]): A list of kubeconfig contexts Tilt is allowed to use. See the Tilt documentation on allow_k8s_contexts for more details.

default_registry (String, default=””): The image registry to use if you need to push images. See the Tilt documentation for more details.

kind_cluster_name (String, default=”capi-test”): The name of the kind cluster to use when preloading images.

provider_repos (Array[]String, default=[]): A list of paths to all the providers you want to use. Each provider must have a tilt-provider.yaml or tilt-provider.json file describing how to build the provider.

enable_providers (Array[]String, default=[‘docker’]): A list of the providers to enable. See available providers for more details.

template_dirs (Map{String: Array[]String}, default={”docker”: [ “./test/infrastructure/docker/templates”]}): A map of providers to directories containing cluster templates. An example of the field is given below. See Deploying a workload cluster for how this is used.

template_dirs:
  docker:
  - ./test/infrastructure/docker/templates
  - <other-template-dir>
  azure:
  - <azure-template-dir>
  aws:
  - <aws-template-dir>
  gcp:
  - <gcp-template-dir>

kustomize_substitutions (Map{String: String}, default={}): An optional map of substitutions for ${}-style placeholders in the provider’s yaml. These substitutions are also used when deploying cluster templates. See Deploying a workload cluster.

Note: When running E2E tests locally using an existing cluster managed by Tilt, the following substitutions are required for successful tests:

kustomize_substitutions:
  CLUSTER_TOPOLOGY: "true"
  EXP_MACHINE_POOL: "true"
  EXP_CLUSTER_RESOURCE_SET: "true"
  EXP_KUBEADM_BOOTSTRAP_FORMAT_IGNITION: "true"
  EXP_RUNTIME_SDK: "true"

For example, if the yaml contains ${AWS_B64ENCODED_CREDENTIALS}, you could do the following:

kustomize_substitutions:
  AWS_B64ENCODED_CREDENTIALS: "your credentials here"

An Azure Service Principal is needed for populating the controller manifests. This utilizes environment-based authentication.

  1. Save your Subscription ID
AZURE_SUBSCRIPTION_ID=$(az account show --query id --output tsv)
az account set --subscription $AZURE_SUBSCRIPTION_ID
  1. Set the Service Principal name
AZURE_SERVICE_PRINCIPAL_NAME=ServicePrincipalName
  1. Save your Tenant ID, Client ID, Client Secret
AZURE_TENANT_ID=$(az account show --query tenantId --output tsv)
AZURE_CLIENT_SECRET=$(az ad sp create-for-rbac --name http://$AZURE_SERVICE_PRINCIPAL_NAME --query password --output tsv)
AZURE_CLIENT_ID=$(az ad sp show --id http://$AZURE_SERVICE_PRINCIPAL_NAME --query appId --output tsv)

Add the output of the following as a section in your tilt-settings.yaml:

  cat <<EOF
  kustomize_substitutions:
     AZURE_SUBSCRIPTION_ID_B64: "$(echo "${AZURE_SUBSCRIPTION_ID}" | tr -d '\n' | base64 | tr -d '\n')"
     AZURE_TENANT_ID_B64: "$(echo "${AZURE_TENANT_ID}" | tr -d '\n' | base64 | tr -d '\n')"
     AZURE_CLIENT_SECRET_B64: "$(echo "${AZURE_CLIENT_SECRET}" | tr -d '\n' | base64 | tr -d '\n')"
     AZURE_CLIENT_ID_B64: "$(echo "${AZURE_CLIENT_ID}" | tr -d '\n' | base64 | tr -d '\n')"
  EOF

kustomize_substitutions:
  DO_B64ENCODED_CREDENTIALS: "your credentials here"

You can generate a base64 version of your GCP json credentials file using:

base64 -i ~/path/to/gcp/credentials.json

kustomize_substitutions:
  GCP_B64ENCODED_CREDENTIALS: "your credentials here"

deploy_observability ([string], default=[]): If set, installs on the dev cluster one of more observability tools. Important! This feature requires the helm command to be available in the user’s path.

Supported values are:

  • grafana*: To create dashboards and query loki as well as prometheus.
  • kube-state-metrics: For exposing metrics for kubernetes and CAPI resources to prometheus.
  • loki: To receive and store logs.
  • prometheus*: For collecting metrics from Kubernetes.
  • promtail: For providing pod logs to loki.
  • visualizer*: Visualize Cluster API resources for each cluster, provide quick access to the specs and status of any resource.

*: Note: the UI will be accessible via a link in the tilt console

debug (Map{string: Map} default{}): A map of named configurations for the provider. The key is the name of the provider.

Supported settings:

  • port (int, default=0 (disabled)): If set to anything other than 0, then Tilt will run the provider with delve and port forward the delve server to localhost on the specified debug port. This can then be used with IDEs such as Visual Studio Code, Goland and IntelliJ.

  • continue (bool, default=true): By default, Tilt will run delve with --continue, such that any provider with debugging turned on will run normally unless specifically having a breakpoint entered. Change to false if you do not want the controller to start at all by default.

  • profiler_port (int, default=0 (disabled)): If set to anything other than 0, then Tilt will enable the profiler with --profiler-address and set up a port forward. A “profiler” link will be visible in the Tilt Web UI for the controller.

  • metrics_port (int, default=0 (disabled)): If set to anything other than 0, then Tilt will port forward to the default metrics port. A “metrics” link will be visible in the Tilt Web UI for the controller.

  • race_detector (bool, default=false) (Linux amd64 only): If enabled, Tilt will compile the specified controller with cgo and statically compile in the system glibc and enable the race detector. Currently, this is only supported when building on Linux amd64 systems. You must install glibc-static or have libc.a available for this to work.

    Example: Using the configuration below:

      debug:
    core:
      continue: false
      port: 30000
      profiler_port: 40000
      metrics_port: 40001
    Wiring up debuggers
    Visual Studio

    When using the example above, the core CAPI controller can be debugged in Visual Studio Code using the following launch configuration:

    {
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Core CAPI Controller",
      "type": "go",
      "request": "attach",
      "mode": "remote",
      "remotePath": "",
      "port": 30000,
      "host": "127.0.0.1",
      "showLog": true,
      "trace": "log",
      "logOutput": "rpc"
    }
  ]
}
    Goland / Intellij

    With the above example, you can configure a Go Remote run/debug configuration pointing at port 30000.


deploy_cert_manager (Boolean, default=true): Deploys cert-manager into the cluster for use for webhook registration.

trigger_mode (String, default=auto): Optional setting to configure if tilt should automatically rebuild on changes. Set to manual to disable auto-rebuilding and require users to trigger rebuilds of individual changed components through the UI.

extra_args (Object, default={}): A mapping of provider to additional arguments to pass to the main binary configured for this provider. Each item in the array will be passed in to the manager for the given provider.

Example:

extra_args:
  kubeadm-bootstrap:
  - --logging-format=json

With this config, the respective managers will be invoked with:

manager --logging-format=json

Create a kind cluster and run Tilt!

To create a pre-configured kind cluster (if you have not already done so) and launch your development environment, run

make tilt-up

This will open the command-line HUD as well as a web browser interface. You can monitor Tilt’s status in either location. After a brief amount of time, you should have a running development environment, and you should now be able to create a cluster. There are example worker cluster configs available. These can be customized for your specific needs.

Deploying a workload cluster

After your kind management cluster is up and running with Tilt, you can deploy a workload clusters in the Tilt web UI based off of YAML templates from the directories specified in the template_dirs field from the tilt-settings.yaml file (default ./test/infrastructure/docker/templates).

Templates should be named according to clusterctl conventions:

  • template files must be named cluster-template-{name}.yaml; those files will be accessible in the Tilt web UI under the label grouping {provider-label}.templates, i.e. CAPD.templates.
  • cluster class files must be named clusterclass-{name}.yaml; those file will be accessible in the Tilt web UI under the label grouping {provider-label}.clusterclasses, i.e. CAPD.clusterclasses.

By selecting one of those items in the Tilt web UI set of buttons will appear, allowing to create - with a dropdown for customizing variable substitutions - or delete clusters. Custom values for variable substitutions can be set using kustomize_substitutions in tilt-settings.yaml, e.g.

kustomize_substitutions:
  NAMESPACE: default
  KUBERNETES_VERSION: v1.26.0
  CONTROL_PLANE_MACHINE_COUNT: 1
  WORKER_MACHINE_COUNT: 3

Cleaning up your kind cluster and development environment

After stopping Tilt, you can clean up your kind cluster and development environment by running

make clean-kind

To remove all generated files, run

make clean

Note that you must run make clean or make clean-charts to fetch new versions of charts deployed using deploy_observability in tilt-settings.yaml.

Use of clusterctl

When the worker cluster has been created using tilt, clusterctl should not be used for management operations; this is because tilt doesn’t initialize providers on the management cluster like clusterctl init does, so some of the clusterctl commands like clusterctl config won’t work.

This limitation is an acceptable trade-off while executing fast dev-test iterations on controllers logic. If instead you are interested in testing clusterctl workflows, you should refer to the clusterctl developer instructions.

Available providers

The following providers are currently defined in the Tiltfile:

  • core: cluster-api itself
  • kubeadm-bootstrap: kubeadm bootstrap provider
  • kubeadm-control-plane: kubeadm control-plane provider
  • docker: Docker infrastructure provider
  • test-extension: Runtime extension used by CAPI E2E tests

Additional providers can be added by following the procedure described in following paragraphs:

tilt-provider configuration

A provider must supply a tilt-provider.yaml file describing how to build it. Here is an example:

name: aws
config:
  image: "gcr.io/k8s-staging-cluster-api-aws/cluster-api-aws-controller"
  live_reload_deps: ["main.go", "go.mod", "go.sum", "api", "cmd", "controllers", "pkg"]
  label: CAPA

config fields

image: the image for this provider, as referenced in the kustomize files. This must match; otherwise, Tilt won’t build it.

live_reload_deps: a list of files/directories to watch. If any of them changes, Tilt rebuilds the manager binary for the provider and performs a live update of the running container.

additional_docker_helper_commands (String, default=””): Additional commands to be run in the helper image docker build. e.g.

RUN wget -qO- https://dl.k8s.io/v1.21.2/kubernetes-client-linux-amd64.tar.gz | tar xvz
RUN wget -qO- https://get.docker.com | sh

additional_docker_build_commands (String, default=””): Additional commands to be appended to the dockerfile. The manager image will use docker-slim, so to download files, use additional_helper_image_commands. e.g.

COPY --from=tilt-helper /usr/bin/docker /usr/bin/docker
COPY --from=tilt-helper /go/kubernetes/client/bin/kubectl /usr/bin/kubectl

kustomize_config (Bool, default=true): Whether or not running kustomize on the ./config folder of the provider. Set to false if your provider does not have a ./config folder or you do not want it to be applied in the cluster.

go_main (String, default=”main.go”): The go main file if not located at the root of the folder

label (String, default=provider name): The label to be used to group provider components in the tilt UI in tilt version >= v0.22.2 (see https://blog.tilt.dev/2021/08/09/resource-grouping.html); as a convention, provider abbreviation should be used (CAPD, KCP etc.).

additional_resources ([]string, default=[]): A list of paths to yaml file to be loaded into the tilt cluster; e.g. use this to deploy an ExtensionConfig object for a RuntimeExtension provider.

resource_deps ([]string, default=[]): A list of tilt resource names to be installed before the current provider; e.g. set this to [“capi_controller”] to ensure that this provider gets installed after Cluster API.

Customizing Tilt

If you need to customize Tilt’s behavior, you can create files in cluster-api’s tilt.d directory. This file is ignored by git so you can be assured that any files you place here will never be checked in to source control.

These files are included after the providers map has been defined and after all the helper function definitions. This is immediately before the “real work” happens.

Under the covers, a.k.a “the real work”

At a high level, the Tiltfile performs the following actions:

  1. Read tilt-settings.yaml
  2. Configure the allowed Kubernetes contexts
  3. Set the default registry
  4. Define the providers map
  5. Include user-defined Tilt files
  6. Deploy cert-manager
  7. Enable providers (core + what is listed in tilt-settings.yaml)
    1. Build the manager binary locally as a local_resource
    2. Invoke docker_build for the provider
    3. Invoke kustomize for the provider’s config/ directory

Live updates

Each provider in the providers map has a live_reload_deps list. This defines the files and/or directories that Tilt should monitor for changes. When a dependency is modified, Tilt rebuilds the provider’s manager binary on your local machine, copies the binary to the running container, and executes a restart script. This is significantly faster than rebuilding the container image for each change. It also helps keep the size of each development image as small as possible (the container images do not need the entire go toolchain, source code, module dependencies, etc.).

IDE support for Tiltfile

For Intellij, Syntax highlighting for the Tiltfile can be configured with a TextMate Bundle. For instructions, please see: Tiltfile TextMate Bundle.

For VSCode the Bazel plugin can be used, it provides syntax highlighting and auto-formatting. To enable it for Tiltfile a file association has to be configured via user settings:

"files.associations": {
  "Tiltfile": "starlark",
},