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Orchestrating a source-to-URL deployment on Kubernetes

A Go sample that shows how to use Knative to go from source code in a git repository to a running application with a URL.

This sample uses the Build and Serving components of Knative to orchestrate an end-to-end deployment.

Prerequisites

You need:

  • A Kubernetes cluster with Knative installed. Follow the installation instructions if you need to create one.
  • Go installed and configured. This is optional, and only required if you want to run the sample app locally.

Configuring Knative

To use this sample, you need to install a build template and register a secret for Docker Hub.

Install the kaniko build template

This sample leverages the kaniko build template to perform a source-to-container build on your Kubernetes cluster.

Use kubectl to install the kaniko manifest:

kubectl apply --filename https://raw.githubusercontent.com/knative/build-templates/master/kaniko/kaniko.yaml

Register secrets for Docker Hub

In order to push the container that is built from source to Docker Hub, register a secret in Kubernetes for authentication with Docker Hub.

There are detailed instructions available, but these are the key steps:

  1. Create a new Secret manifest, which is used to store your Docker Hub credentials. Save this file as docker-secret.yaml:

    apiVersion: v1
kind: Secret
metadata:
  name: basic-user-pass
  annotations:
    build.knative.dev/docker-0: https://index.docker.io/v1/
type: kubernetes.io/basic-auth
data:
  # Use 'echo -n "username" | base64' to generate this string
  username: BASE64_ENCODED_USERNAME
  # Use 'echo -n "password" | base64' to generate this string
  password: BASE64_ENCODED_PASSWORD

  2. On macOS or Linux computers, use the following command to generate the base64-encoded values required for the manifest:

    $ echo -n "username" | base64 -w 0
dXNlcm5hbWU=

$ echo -n "password" | base64 -w 0
cGFzc3dvcmQ=

    Note: If you receive the "invalid option -w" error on macOS, try using the base64 -b 0 command.

  3. Create a new Service Account manifest which is used to link the build process to the secret. Save this file as service-account.yaml:

     apiVersion: v1
 kind: ServiceAccount
 metadata:
   name: build-bot
 secrets:
 - name: basic-user-pass

  4. After you have created the manifest files, apply them to your cluster with kubectl:

    $ kubectl apply --filename docker-secret.yaml
secret "basic-user-pass" created
$ kubectl apply --filename service-account.yaml
serviceaccount "build-bot" created

Deploying the sample

Now that you've configured your cluster accordingly, you are ready to deploy the sample service into your cluster.

This sample uses github.com/mchmarny/simple-app as a basic Go application, but you could replace this GitHub repo with your own. The only requirements are that the repo must contain a Dockerfile with the instructions for how to build a container for the application.

  1. You need to create a service manifest which defines the service to deploy, including where the source code is and which build-template to use. Create a file named service.yaml and copy the following definition. Make sure to replace {DOCKER_USERNAME} with your own Docker Hub username:

    apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: app-from-source
  namespace: default
spec:
  runLatest:
    configuration:
      build:
        serviceAccountName: build-bot
        source:
          git:
            url: https://github.com/mchmarny/simple-app.git
            revision: master
        template:
          name: kaniko
          arguments:
          - name: IMAGE
            value: docker.io/{DOCKER_USERNAME}/app-from-source:latest
      revisionTemplate:
        spec:
          container:
            image: docker.io/{DOCKER_USERNAME}/app-from-source:latest 
            imagePullPolicy: Always
            env:
            - name: SIMPLE_MSG
              value: "Hello sample app!"

  2. Apply this manifest using kubectl, and watch the results:

    # Apply the manifest
$ kubectl apply --filename service.yaml
service "app-from-source" created

# Watch the pods for build and serving
$ kubectl get pods --watch
NAME                          READY     STATUS       RESTARTS   AGE
app-from-source-00001-zhddx   0/1       Init:2/3     0          7s
app-from-source-00001-zhddx   0/1       PodInitializing   0         37s
app-from-source-00001-zhddx   0/1       Completed   0         38s
app-from-source-00001-deployment-6d6ff665f9-xfhm5   0/3       Pending   0         0s
app-from-source-00001-deployment-6d6ff665f9-xfhm5   0/3       Pending   0         0s
app-from-source-00001-deployment-6d6ff665f9-xfhm5   0/3       Init:0/1   0         0s
app-from-source-00001-deployment-6d6ff665f9-xfhm5   0/3       Init:0/1   0         2s
app-from-source-00001-deployment-6d6ff665f9-xfhm5   0/3       PodInitializing   0         3s
app-from-source-00001-deployment-6d6ff665f9-xfhm5   2/3       Running   0         6s
app-from-source-00001-deployment-6d6ff665f9-xfhm5   3/3       Running   0         11s

  3. Once you see the deployment pod switch to the running state, press Ctrl+C to escape the watch. Your container is now built and deployed!

  4. To check on the state of the service, get the service object and examine the status block:

    $ kubectl get service.serving.knative.dev app-from-source --output yaml

[...]
status:
  conditions:
  - lastTransitionTime: 2018-07-11T20:50:18Z
    status: "True"
    type: ConfigurationsReady
  - lastTransitionTime: 2018-07-11T20:50:56Z
    status: "True"
    type: RoutesReady
  - lastTransitionTime: 2018-07-11T20:50:56Z
    status: "True"
    type: Ready
  domain: app-from-source.default.example.com
  latestCreatedRevisionName: app-from-source-00007
  latestReadyRevisionName: app-from-source-00007
  observedGeneration: 10
  traffic:
  - configurationName: app-from-source
   percent: 100
    revisionName: app-from-source-00007

  5. Now that your service is created, Knative will perform the following steps:

    • Fetch the revision specified from GitHub and build it into a container
    • Push the container to Docker Hub
    • Create a new immutable revision for this version of the app.
    • Network programming to create a route, ingress, service, and load balance for your app.
    • Automatically scale your pods up and down (including to zero active pods).

  6. To get the ingress IP for your cluster, use the following command. If your cluster is new, it can take some time for the service to get an external IP address:

    $ kubectl get svc knative-ingressgateway --namespace istio-system

NAME                     TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)                                      AGE
knative-ingressgateway   LoadBalancer   10.23.247.74   35.203.155.229   80:32380/TCP,443:32390/TCP,32400:32400/TCP   2d

  7. To find the URL for your service, type:

    $ kubectl get services.serving.knative.dev app-from-source  --output=custom-columns=NAME:.metadata.name,DOMAIN:.status.domain
NAME                DOMAIN
app-from-source     app-from-source.default.example.com

  8. Now you can make a request to your app to see the result. Replace {IP_ADDRESS} with the address that you got in the previous step:

    curl -H "Host: app-from-source.default.example.com" http://{IP_ADDRESS}
Hello World!

Removing the sample app deployment

To remove the sample app from your cluster, delete the service record:

kubectl delete --filename service.yaml

Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License.