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Development

This doc explains how to set up a development environment so you can get started contributing to Knative Serving. Also take a look at:

Prerequisites

Follow the instructions below to set up your development environment. Once you meet these requirements, you can make changes and deploy your own version of Knative Serving!

Before submitting a PR, see also CONTRIBUTING.md.

Sign up for GitHub

Start by creating a GitHub account, then set up GitHub access via SSH.

Install requirements

Getting started with GitHub Codespaces

To get started, create a codespace for this repository by clicking this 👇

Open in GitHub Codespaces

A codespace will open in a web-based version of Visual Studio Code. The dev container is fully configured with software needed for this project. It creates a local container registry, a Kind cluster and deploys Knative Serving and Knative Ingress. If you use a codespace, then you can directly skip to the Iterating section of this document.

Note: Dev containers is an open spec which is supported by GitHub Codespaces and other tools.

Local Setup

You must install these tools:

  1. go: The language Knative Serving is built-in (1.16 or later)
  2. git: For source control
  3. ko: For development.
  4. kubectl: For managing development environments.
  5. bash v4 or later. On macOS the default bash is too old, you can use Homebrew to install a later version.

If you're working on and changing .proto files:

  1. protoc: For compiling protocol buffers.
  2. protoc-gen-gogofaster: For generating efficient golang code out of protocol buffers.

Create a cluster and a repo

  1. Set up a Kubernetes cluster
    • Minimum supported version is 1.20.0
    • Follow the instructions in the Kubernetes doc.
  2. Set up a docker repository for pushing images. You can use any container image registry by adjusting the authentication methods and repository paths mentioned in the sections below.
    • Google Container Registry quickstart
    • Docker Hub quickstart
    • If developing locally with Docker or Minikube, you can set KO_DOCKER_REPO=ko.local (preferred) or use the -L flag to ko to build and push locally (in this case, authentication is not needed). If developing with Kind you can set KO_DOCKER_REPO=kind.local.
    • If you encounter an ImagePullBackOff error while using Minikube or Kind, it may be due to the cluster's inability to pull locally built images because of image pull policies. To resolve this issue, consider enabling the local registry: for Minikube or for Kind.

Note: You'll need to be authenticated with your KO_DOCKER_REPO before pushing images. Run gcloud auth configure-docker if you are using Google Container Registry or docker login if you are using Docker Hub.

Set up your environment

To start your environment you'll need to set the following environment variable (we recommend adding it to your .bashrc):

  1. KO_DOCKER_REPO: The docker repository to which developer images should be pushed (e.g. gcr.io/[gcloud-project]).
  • Note: if you are using docker hub to store your images your KO_DOCKER_REPO variable should be docker.io/<username>.
  • Note: Currently Docker Hub doesn't let you create subdirs under your username.

.bashrc example:

export KO_DOCKER_REPO='gcr.io/my-gcloud-project-id'

Check out your fork

To check out this repository:

  1. Create your own fork of this repo
  2. Clone it to your machine:
git clone [email protected]:${YOUR_GITHUB_USERNAME}/serving.git
cd serving
git remote add upstream https://github.com/knative/serving.git
git remote set-url --push upstream no_push

Adding the upstream remote sets you up nicely for regularly syncing your fork.

Once you reach this point you are ready to do a full build and deploy as described below.

Starting Knative Serving

Once you've set up your development environment, stand up Knative Serving. Note that if you already installed Knative to your cluster, redeploying the new version should work fine, but if you run into trouble, you can easily clean your cluster up and try again.

Enter the serving directory to install the following components.

Set up cluster-admin

Your user must be a cluster-admin to perform the setup needed for Knative. This should be the case by default if you've provisioned your own Kubernetes cluster. In particular, you'll need to be able to create Kubernetes cluster-scoped Namespace, CustomResourceDefinition, ClusterRole, and ClusterRoleBinding objects.

Resource allocation for Kubernetes

Please allocate sufficient resources for Kubernetes, especially when you run a Kubernetes cluster on your local machine. We recommend allocating at least 6 CPUs and 8G memory assuming a single node Kubernetes installation, and allocating at least 4 CPUs and 8G memory for each node assuming a 3-node Kubernetes installation. Please go back to your cluster setup to reconfigure your Kubernetes cluster in your designated environment, if necessary.

Deploy cert-manager

  1. Deploy cert-manager

    kubectl apply -f ./third_party/cert-manager-latest/cert-manager.yaml
kubectl wait --for=condition=Established --all crd
kubectl wait --for=condition=Available -n cert-manager --all deployments

Deploy Knative Serving

  • This step includes building Knative Serving, creating and pushing developer images, and deploying them to your Kubernetes cluster. If you're developing locally, set KO_DOCKER_REPO=ko.local (or KO_DOCKER_REPO=kind.local respectively) to avoid needing to push your images to an off-machine registry.

  • By default, ko will build container images for the architecture of your local machine, but if you need to build images for a different platform (OS and architecture), you can provide --platform flag as follows:

    # Synopsis
ko apply -f FILENAME [flags]

# Usage
ko apply --selector knative.dev/crd-install=true -Rf config/core/ --platform linux/arm64

Run:

ko apply --selector knative.dev/crd-install=true -Rf config/core/
kubectl wait --for=condition=Established --all crd

ko apply -Rf config/core/

# Optional steps

# Run post-install job to set up a nice sslip.io domain name.  This only works
# if your Kubernetes LoadBalancer has an IPv4 address.
ko delete -f config/post-install/default-domain.yaml --ignore-not-found
ko apply -f config/post-install/default-domain.yaml

The above step is equivalent to applying the serving-crds.yaml, serving-core.yaml, serving-hpa.yaml and serving-nscert.yaml for released versions of Knative Serving.

You can see things running with:

kubectl -n knative-serving get pods
NAME                                     READY   STATUS    RESTARTS   AGE
activator-7454cd659f-rrz86               1/1     Running   0          105s
autoscaler-58cbfd4985-fl5h7              1/1     Running   0          105s
autoscaler-hpa-77964b9b8c-9sbgq          1/1     Running   0          105s
controller-847b7cc977-5mvvq              1/1     Running   0          105s
webhook-6b6c77567f-flr59                 1/1     Running   0          105s

You can access the Knative Serving Controller's logs with:

kubectl -n knative-serving logs $(kubectl -n knative-serving get pods -l app=controller -o name) -c controller

If you're using a GCP project to host your Kubernetes cluster, it's good to check the Discovery & load balancing page to ensure that all services are up and running (and not blocked by a quota issue, for example).

Deploy Knative Ingress

Knative supports a variety of Ingress solutions.

For simplicity, you can just run the following command to install Kourier.

kubectl apply -f ./third_party/kourier-latest/kourier.yaml

kubectl patch configmap/config-network \
  -n knative-serving \
  --type merge \
  -p '{"data":{"ingress.class":"kourier.ingress.networking.knative.dev"}}'

If you want to choose another Ingress solution, you can follow the instructions in the Knative installation doc to pick up an alternative Ingress solution and install it.

Iterating

As you make changes to the code-base, there are several special cases to be aware of:

  • If you change an input to generated code, then you must run ./hack/update-codegen.sh. Inputs include:

    • API type definitions in pkg/apis/serving/v1/.
    • Type definitions annotated with // +k8s:deepcopy-gen=true.
    • The _example value of config maps (to keep the knative.dev/example-checksum annotations in sync). These can also be individually updated using ./hack/update-checksums.sh.
    • .proto files. Run ./hack/update-codegen.sh with the --generate-protobufs flag to enable protocol buffer generation.

  • If you change a package's deps (including adding an external dependency), then you must run ./hack/update-deps.sh.

  • If you change surface area of PodSpec that we allow in our resources then you must update the relevant section of ./hack/schemapatch-config.yaml and run ./hack/update-schemas.sh Additionally:

    • If the new field is added behind a feature flag, then add the kubebuilder:validation:DropProperties and kubebuilder:pruning:PreserveUnknownFields as additionalMarkers.

      additionalMarkers:
# Part of a feature flag - so we want to omit the schema and preserve unknown fields
- kubebuilder:validation:DropProperties
- kubebuilder:pruning:PreserveUnknownFields

These are all idempotent, and we expect that running these at HEAD to have no diffs. Code generation and dependencies are automatically checked to produce no diffs for each pull request.

update-deps.sh runs go get/mod command. In some cases, if newer dependencies are required, you need to run "go get" manually.

Once the codegen, dependency, and schema information is correct, redeploying the controller is simply:

ko apply -f config/core/deployments/controller.yaml

Or you can clean it up completely and completely redeploy Knative Serving.

Updating existing dependencies

To update existing dependencies execute

./hack/update-deps.sh --upgrade && ./hack/update-codegen.sh

Clean up

You can delete all of the serving components with:

ko delete --ignore-not-found=true \
  -Rf config/core/ \
  -f ./third_party/kourier-latest/kourier.yaml \
  -f ./third_party/cert-manager-latest/cert-manager.yaml