actions-runner-controller

This controller operates self-hosted runners for GitHub Actions on your Kubernetes cluster.

ToC:

Motivation
Installation
- GitHub Enterprise support
Setting up authentication with GitHub API
- Using GitHub App
- Using Personal AccessToken
Usage
Developing
Alternatives

Motivation

GitHub Actions is a very useful tool for automating development. GitHub Actions jobs are run in the cloud by default, but you may want to run your jobs in your environment. Self-hosted runner can be used for such use cases, but requires the provisioning and configuration of a virtual machine instance. Instead if you already have a Kubernetes cluster, it makes more sense to run the self-hosted runner on top of it.

actions-runner-controller makes that possible. Just create a Runner resource on your Kubernetes, and it will run and operate the self-hosted runner for the specified repository. Combined with Kubernetes RBAC, you can also build simple Self-hosted runners as a Service.

Installation

actions-runner-controller uses cert-manager for certificate management of Admission Webhook. Make sure you have already installed cert-manager before you install. The installation instructions for cert-manager can be found below.

Installing cert-manager on Kubernetes

Install the custom resource and actions-runner-controller with kubectl or helm. This will create actions-runner-system namespace in your Kubernetes and deploy the required resources.

kubectl:

# REPLACE "v0.16.1" with the latest release
kubectl apply -f https://github.com/summerwind/actions-runner-controller/releases/download/v0.16.1/actions-runner-controller.yaml

helm:

helm repo add actions-runner-controller https://summerwind.github.io/actions-runner-controller
helm upgrade --install -n actions-runner-system actions-runner-controller/actions-runner-controller

Github Enterprise support

If you use either Github Enterprise Cloud or Server, you can use actions-runner-controller with those, too. Authentication works same way as with public Github (repo and organization level). The minimum version of Github Enterprise Server is 3.0.0 (or rc1/rc2). In most cases maintainers do not have environment where to test changes and are reliant on the community for testing.

kubectl set env deploy controller-manager -c manager GITHUB_ENTERPRISE_URL=<GHEC/S URL> --namespace actions-runner-system

Enterprise runners usage

In order to use enterprise runners you must have Admin access to Github Enterprise and you should do Personal Access Token (PAT) with enterprise:admin access. Enterprise runners are not possible to run with Github APP or any other permission.

When you use enterprise runners those will get access to Github Organisations. However, access to the repositories is NOT allowed by default. Each Github Organisation must allow Enterprise runner groups to be used in repositories. This is needed only one time and is permanent after that.

Example:

apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: ghe-runner-deployment
spec:
  replicas: 2
  template:
    spec:
      enterprise: your-enterprise-name
      dockerdWithinRunnerContainer: true
      resources:
        limits:
          cpu: "4000m"
          memory: "2Gi"
        requests:
          cpu: "200m"
          memory: "200Mi"
      volumeMounts:
      - mountPath: /runner
        name: runner
      volumes:
      - name: runner
        emptyDir: {}

Setting up authentication with GitHub API

There are two ways for actions-runner-controller to authenticate with the GitHub API:

Using GitHub App.
Using Personal Access Token.

Regardless of which authentication method you use, the same permissions are required, those permissions are:

Repository: Administration (read/write)
Repository: Actions (read)
Organization: Self-hosted runners (read/write)

NOTE: It is extremely important to only follow one of the sections below and not both.

Using GitHub App

You can create a GitHub App for either your account or any organization. If you want to create a GitHub App for your account, open the following link to the creation page, enter any unique name in the "GitHub App name" field, and hit the "Create GitHub App" button at the bottom of the page.

Create GitHub Apps on your account

If you want to create a GitHub App for your organization, replace the :org part of the following URL with your organization name before opening it. Then enter any unique name in the "GitHub App name" field, and hit the "Create GitHub App" button at the bottom of the page to create a GitHub App.

Create GitHub Apps on your organization

You will see an App ID on the page of the GitHub App you created as follows, the value of this App ID will be used later.

Download the private key file by pushing the "Generate a private key" button at the bottom of the GitHub App page. This file will also be used later.

Go to the "Install App" tab on the left side of the page and install the GitHub App that you created for your account or organization.

When the installation is complete, you will be taken to a URL in one of the following formats, the last number of the URL will be used as the Installation ID later (For example, if the URL ends in settings/installations/12345, then the Installation ID is 12345).

https://github.com/settings/installations/${INSTALLATION_ID}
https://github.com/organizations/eventreactor/settings/installations/${INSTALLATION_ID}

Finally, register the App ID (APP_ID), Installation ID (INSTALLATION_ID), and downloaded private key file (PRIVATE_KEY_FILE_PATH) to Kubernetes as Secret.

$ kubectl create secret generic controller-manager \
    -n actions-runner-system \
    --from-literal=github_app_id=${APP_ID} \
    --from-literal=github_app_installation_id=${INSTALLATION_ID} \
    --from-file=github_app_private_key=${PRIVATE_KEY_FILE_PATH}

Using Personal Access Token

From an account that has admin privileges for the repository, create a personal access token with repo scope. This token is used to register a self-hosted runner by actions-runner-controller.

Self-hosted runners in GitHub can either be connected to a single repository, or to a GitHub organization (so they are available to all repositories in the organization). This token is used to register a self-hosted runner by actions-runner-controller.

For adding a runner to a repository, the token should have repo scope. If the runner should be added to an organization, the token should have admin:org scope. Note that to use a Personal Access Token, you must issue the token with an account that has admin privileges (on the repository and/or the organization).

Open the Create Token page from the following link, grant the repo and/or admin:org scope, and press the "Generate Token" button at the bottom of the page to create the token.

Create personal access token

Register the created token (GITHUB_TOKEN) as a Kubernetes secret.

kubectl create secret generic controller-manager \
    -n actions-runner-system \
    --from-literal=github_token=${GITHUB_TOKEN}

Usage

There are two ways to use this controller:

Manage runners one by one with Runner.
Manage a set of runners with RunnerDeployment.

Repository runners

To launch a single self-hosted runner, you need to create a manifest file includes Runner resource as follows. This example launches a self-hosted runner with name example-runner for the summerwind/actions-runner-controller repository.

# runner.yaml
apiVersion: actions.summerwind.dev/v1alpha1
kind: Runner
metadata:
  name: example-runner
spec:
  repository: summerwind/actions-runner-controller
  env: []

Apply the created manifest file to your Kubernetes.

$ kubectl apply -f runner.yaml
runner.actions.summerwind.dev/example-runner created

You can see that the Runner resource has been created.

$ kubectl get runners
NAME             REPOSITORY                             STATUS
example-runner   summerwind/actions-runner-controller   Running

You can also see that the runner pod has been running.

$ kubectl get pods
NAME           READY   STATUS    RESTARTS   AGE
example-runner 2/2     Running   0          1m

The runner you created has been registered to your repository.

Now you can use your self-hosted runner. See the official documentation on how to run a job with it.

Organization Runners

To add the runner to an organization, you only need to replace the repository field with organization, so the runner will register itself to the organization.

# runner.yaml
apiVersion: actions.summerwind.dev/v1alpha1
kind: Runner
metadata:
  name: example-org-runner
spec:
  organization: your-organization-name

Now you can see the runner on the organization level (if you have organization owner permissions).

RunnerDeployments

There are RunnerReplicaSet and RunnerDeployment that corresponds to ReplicaSet and Deployment but for Runner.

You usually need only RunnerDeployment rather than RunnerReplicaSet as the former is for managing the latter.

# runnerdeployment.yaml
apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: example-runnerdeploy
spec:
  replicas: 2
  template:
    spec:
      repository: mumoshu/actions-runner-controller-ci
      env: []

Apply the manifest file to your cluster:

$ kubectl apply -f runner.yaml
runnerdeployment.actions.summerwind.dev/example-runnerdeploy created

You can see that 2 runners have been created as specified by replicas: 2:

$ kubectl get runners
NAME                             REPOSITORY                             STATUS
example-runnerdeploy2475h595fr   mumoshu/actions-runner-controller-ci   Running
example-runnerdeploy2475ht2qbr   mumoshu/actions-runner-controller-ci   Running

Autoscaling

RunnerDeployment can scale the number of runners between minReplicas and maxReplicas fields, depending on pending workflow runs.

In the below example, actions-runner checks for pending workflow runs for each sync period, and scale to e.g. 3 if there're 3 pending jobs at sync time.

apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: example-runner-deployment
spec:
  template:
    spec:
      repository: summerwind/actions-runner-controller
---
apiVersion: actions.summerwind.dev/v1alpha1
kind: HorizontalRunnerAutoscaler
metadata:
  name: example-runner-deployment-autoscaler
spec:
  scaleTargetRef:
    name: example-runner-deployment
  minReplicas: 1
  maxReplicas: 3
  metrics:
  - type: TotalNumberOfQueuedAndInProgressWorkflowRuns
    repositoryNames:
    - summerwind/actions-runner-controller

The scale out performance is controlled via the manager containers startup --sync-period argument. The default value is 10 minutes to prevent unconfigured deployments rate limiting themselves from the GitHub API. The period can be customised in the config/default/manager_auth_proxy_patch.yaml patch for those that are building the solution via the kustomize setup.

Additionally, the autoscaling feature has an anti-flapping option that prevents periodic loop of scaling up and down. By default, it doesn't scale down until the grace period of 10 minutes passes after a scale up. The grace period can be configured by setting scaleDownDelaySecondsAfterScaleUp:

apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: example-runner-deployment
spec:
  template:
    spec:
      repository: summerwind/actions-runner-controller
---
apiVersion: actions.summerwind.dev/v1alpha1
kind: HorizontalRunnerAutoscaler
metadata:
  name: example-runner-deployment-autoscaler
spec:
  scaleTargetRef:
    name: example-runner-deployment
  minReplicas: 1
  maxReplicas: 3
  scaleDownDelaySecondsAfterScaleOut: 60
  metrics:
  - type: TotalNumberOfQueuedAndInProgressWorkflowRuns
    repositoryNames:
    - summerwind/actions-runner-controller

If you do not want to manage an explicit list of repositories to scale, an alternate autoscaling scheme that can be applied is the PercentageRunnersBusy scheme. The number of desired pods are evaulated by checking how many runners are currently busy and applying a scaleup or scale down factor if certain thresholds are met. By setting the metric type to PercentageRunnersBusy, the HorizontalRunnerAutoscaler will query github for the number of busy runners which live in the RunnerDeployment namespace. Scaleup and scaledown thresholds are the percentage of busy runners at which the number of desired runners are re-evaluated. Scaleup and scaledown factors are the multiplicative factor applied to the current number of runners used to calculate the number of desired runners. This scheme is also especially useful if you want multiple controllers in various clusters, each responsible for scaling their own runner pods per namespace.

---
apiVersion: actions.summerwind.dev/v1alpha1
kind: HorizontalRunnerAutoscaler
metadata:
  name: example-runner-deployment-autoscaler
spec:
  scaleTargetRef:
    name: example-runner-deployment
  minReplicas: 1
  maxReplicas: 3
  scaleDownDelaySecondsAfterScaleOut: 60
  metrics:
  - type: PercentageRunnersBusy
    scaleUpThreshold: '0.75'
    scaleDownThreshold: '0.3'
    scaleUpFactor: '1.4'
    scaleDownFactor: '0.7'

Faster Autoscaling with GitHub Webhook

This feature is an ADVANCED feature which may require more work to set up. Please get prepared to put some time and effort to learn and leverage this feature!

actions-runner-controller has an optional Webhook server that receives GitHub Webhook events and scale RunnerDeployments by updating corresponding HorizontalRunnerAutoscalers.

Today, the Webhook server can be configured to respond GitHub check_run, pull_request, and push events by scaling up the matching HorizontalRunnerAutoscaler by N replica(s), where N is configurable within HorizontalRunerAutoscaler's Spec.

More concretely, you can configure the targeted GitHub event types and the N in scaleUpTriggers:

kind: HorizontalRunnerAutoscaler
spec:
  scaleTargetRef:
    name: myrunners
  scaleUpTrigggers:
  - githubEvent:
      checkRun:
        types: ["created"]
        status: "queued"
    amount: 1
    duration: "5m"

With the above example, the webhook server scales myrunners by 1 replica for 5 minutes on each check_run event with the type of created and the status of queued received.

The primary benefit of autoscaling on Webhook compared to the standard autoscaling is that this one allows you to immediately add "resource slack" for future GitHub Actions job runs.

In contrast, the standard autoscaling requires you to wait next sync period to add insufficient runners. You can definitely shorten the sync period to make the standard autoscaling more responsive. But doing so eventually result in the controller not functional due to GitHub API rate limit.

You can learn the implementation details in #282

To enable this feature, you firstly need to install the webhook server.

Currently, only our Helm chart has the ability install it.

$ helm --upgrade install actions-runner-controller/actions-runner-controller \
  githubWebhookServer.enabled=true \
  githubWebhookServer.ports[0].nodePort=33080

The above command will result in exposing the node port 33080 for Webhook events. Usually, you need to create an external loadbalancer targeted to the node port, and register the hostname or the IP address of the external loadbalancer to the GitHub Webhook.

Once you were able to confirm that the Webhook server is ready and running from GitHub - this is usually verified by the GitHub sending PING events to the Webhook server - create or update your HorizontalRunnerAutoscaler resources by learning the following configuration examples.

Example 1: Scale up on each check_run event
Example 2: Scale on each pull_request event against develop or main branches

Example 1: Scale up on each `check_run` event

Note: This should work almost like https://github.com/philips-labs/terraform-aws-github-runner

To scale up replicas of the runners for example/myrepo by 1 for 5 minutes on each check_run, you write manifests like the below:

kind: RunnerDeployment
metadata:
   name: myrunners
spec:
  repository: example/myrepo
---
kind: HorizontalRunnerAutoscaler
spec:
  scaleTargetRef:
    name: myrunners
  scaleUpTrigggers:
  - githubEvent:
      checkRun:
        types: ["created"]
        status: "queued"
    amount: 1
    duration: "5m"

Example 2: Scale on each `pull_request` event against `develop` or `main` branches

kind: RunnerDeployment:
metadata:
   name: myrunners
spec:
  repository: example/myrepo
---
kind: HorizontalRunnerAutoscaler
spec:
  scaleTargetRef:
    name: myrunners
  scaleUpTrigggers:
  - githubEvent:
      pullRequest:
        types: ["synchronize"]
        branches: ["main", "develop"]
    amount: 1
    duration: "5m"

See "activity types" for the list of valid values for scaleUpTriggers[].githubEvent.pullRequest.types.

Runner with DinD

When using default runner, runner pod starts up 2 containers: runner and DinD (Docker-in-Docker). This might create issues if there's LimitRange set to namespace.

# dindrunnerdeployment.yaml
apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: example-dindrunnerdeploy
spec:
  replicas: 2
  template:
    spec:
      image: summerwind/actions-runner-dind
      dockerdWithinRunnerContainer: true
      repository: mumoshu/actions-runner-controller-ci
      env: []

This also helps with resources, as you don't need to give resources separately to docker and runner.

Additional tweaks

You can pass details through the spec selector. Here's an eg. of what you may like to do:

apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: actions-runner
  namespace: default
spec:
  replicas: 2
  template:
    spec:
      nodeSelector:
        node-role.kubernetes.io/test: ""

      tolerations:
      - effect: NoSchedule
        key: node-role.kubernetes.io/test
        operator: Exists

      repository: mumoshu/actions-runner-controller-ci
      image: custom-image/actions-runner:latest
      imagePullPolicy: Always
      resources:
        limits:
          cpu: "4.0"
          memory: "8Gi"
        requests:
          cpu: "2.0"
          memory: "4Gi"

      # Timeout after a node crashed or became unreachable to evict your pods somewhere else (default 5mins)
      tolerations:
        - key: "node.kubernetes.io/unreachable"
          operator: "Exists"
          effect: "NoExecute"
          tolerationSeconds: 10

      # If set to false, there are no privileged container and you cannot use docker.
      dockerEnabled: false
      # If set to true, runner pod container only 1 container that's expected to be able to run docker, too.
      # image summerwind/actions-runner-dind or custom one should be used with true -value
      dockerdWithinRunnerContainer: false
      # Valid if dockerdWithinRunnerContainer is not true
      dockerdContainerResources:
        limits:
          cpu: "4.0"
          memory: "8Gi"
        requests:
          cpu: "2.0"
          memory: "4Gi"
      sidecarContainers:
        - name: mysql
          image: mysql:5.7
          env:
            - name: MYSQL_ROOT_PASSWORD
              value: abcd1234
          securityContext:
            runAsUser: 0
      # if workDir is not specified, the default working directory is /runner/_work
      # this setting allows you to customize the working directory location
      # for example, the below setting is the same as on the ubuntu-18.04 image
      workDir: /home/runner/work

Runner labels

To run a workflow job on a self-hosted runner, you can use the following syntax in your workflow:

jobs:
  release:
    runs-on: self-hosted

When you have multiple kinds of self-hosted runners, you can distinguish between them using labels. In order to do so, you can specify one or more labels in your Runner or RunnerDeployment spec.

# runnerdeployment.yaml
apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: custom-runner
spec:
  replicas: 1
  template:
    spec:
      repository: summerwind/actions-runner-controller
      labels:
        - custom-runner

Once this spec is applied, you can observe the labels for your runner from the repository or organization in the GitHub settings page for the repository or organization. You can now select a specific runner from your workflow by using the label in runs-on:

jobs:
  release:
    runs-on: custom-runner

Note that if you specify self-hosted in your workflow, then this will run your job on any self-hosted runner, regardless of the labels that they have.

Runner Groups

Runner groups can be used to limit which repositories are able to use the GitHub Runner at an Organisation level. Runner groups have to be created in GitHub first before they can be referenced.

To add the runner to the group NewGroup, specify the group in your Runner or RunnerDeployment spec.

# runnerdeployment.yaml
apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: custom-runner
spec:
  replicas: 1
  template:
    spec:
      group: NewGroup

Using EKS IAM role for service accounts

actions-runner-controller v0.15.0 or later has support for EKS IAM role for service accounts.

As similar as for regular pods and deployments, you firstly need an existing service account with the IAM role associated. Create one using e.g. eksctl. You can refer to the EKS documentation for more details.

Once you set up the service account, all you need is to add serviceAccountName and fsGroup to any pods that uses the IAM-role enabled service account.

For RunnerDeployment, you can set those two fields under the runner spec at RunnerDeployment.Spec.Template:

apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: example-runnerdeploy
spec:
  template:
    spec:
      repository: USER/REO
      serviceAccountName: my-service-account
      securityContext:
        fsGroup: 1447

Software installed in the runner image

The GitHub hosted runners include a large amount of pre-installed software packages. For Ubuntu 18.04, this list can be found at https://github.com/actions/virtual-environments/blob/master/images/linux/Ubuntu1804-README.md

The container image is based on Ubuntu 18.04, but it does not contain all of the software installed on the GitHub runners. It contains the following subset of packages from the GitHub runners:

Basic CLI packages
git (2.26)
docker
build-essentials

The virtual environments from GitHub contain a lot more software packages (different versions of Java, Node.js, Golang, .NET, etc) which are not provided in the runner image. Most of these have dedicated setup actions which allow the tools to be installed on-demand in a workflow, for example: actions/setup-java or actions/setup-node

If there is a need to include packages in the runner image for which there is no setup action, then this can be achieved by building a custom container image for the runner. The easiest way is to start with the summerwind/actions-runner image and installing the extra dependencies directly in the docker image:

FROM summerwind/actions-runner:latest

RUN sudo apt update -y \
  && sudo apt install YOUR_PACKAGE
  && sudo rm -rf /var/lib/apt/lists/*

You can then configure the runner to use a custom docker image by configuring the image field of a Runner or RunnerDeployment:

apiVersion: actions.summerwind.dev/v1alpha1
kind: Runner
metadata:
  name: custom-runner
spec:
  repository: summerwind/actions-runner-controller
  image: YOUR_CUSTOM_DOCKER_IMAGE

Common Errors

invalid header field value

2020-11-12T22:17:30.693Z	ERROR	controller-runtime.controller	Reconciler error	{"controller": "runner", "request": "actions-runner-system/runner-deployment-dk7q8-dk5c9", "error": "failed to create registration token: Post \"https://api.github.com/orgs/$YOUR_ORG_HERE/actions/runners/registration-token\": net/http: invalid header field value \"Bearer $YOUR_TOKEN_HERE\\n\" for key Authorization"}

Solutions
Your base64'ed PAT token has a new line at the end, it needs to be created without a \n added

echo -n $TOKEN | base64
Create the secret as described in the docs using the shell and documeneted flags

Developing

If you'd like to modify the controller to fork or contribute, I'd suggest using the following snippet for running the acceptance test:

# This sets `VERSION` envvar to some appropriate value
. hack/make-env.sh

NAME=$DOCKER_USER/actions-runner-controller \
  GITHUB_TOKEN=*** \
  APP_ID=*** \
  PRIVATE_KEY_FILE_PATH=path/to/pem/file \
  INSTALLATION_ID=*** \
  make docker-build docker-push acceptance

Please follow the instructions explained in Using Personal Access Token to obtain GITHUB_TOKEN, and those in Using GitHub App to obtain APP_ID, INSTALLATION_ID, and PRIAVTE_KEY_FILE_PATH.

The test creates a one-off kind cluster, deploys cert-manager and actions-runner-controller, creates a RunnerDeployment custom resource for a public Git repository to confirm that the controller is able to bring up a runner pod with the actions runner registration token installed.

If you prefer to test in a non-kind cluster, you can instead run:

KUBECONFIG=path/to/kubeconfig \
NAME=$DOCKER_USER/actions-runner-controller \
  GITHUB_TOKEN=*** \
  APP_ID=*** \
  PRIVATE_KEY_FILE_PATH=path/to/pem/file \
  INSTALLATION_ID=*** \
  ACCEPTANCE_TEST_SECRET_TYPE=token \
  make docker-build docker-push \
       acceptance/setup acceptance/tests

Alternatives

The following is a list of alternative solutions that may better fit you depending on your use-case:

https://github.com/evryfs/github-actions-runner-operator/

Although the situation can change over time, as of writing this sentence, the benefits of using actions-runner-controller over the alternatives are:

actions-runner-controller has the ability to autoscale runners based on number of pending/progressing jobs (#99)
actions-runner-controller is able to gracefully stop runners (#103)
actions-runner-controller has ARM support

License

audip/actions-runner-controller

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