helloworld

README

Helloworld

A simple web server written in Go that you can use for testing. It reads in an env variable 'TARGET' and prints "Hello World: ${TARGET}!" if TARGET is not specified, it will use "NOT SPECIFIED" as the TARGET.

Prerequisites

1. Install Knative Serving
2. Install docker

Setup

Build the app container and publish it to your registry of choice:

REPO="gcr.io/<your-project-here>"

# Build and publish the container, run from the root directory.
docker build \
  --build-arg SAMPLE=helloworld \
  --tag "${REPO}/sample/helloworld" \
  --file=sample/Dockerfile.golang .
docker push "${REPO}/sample/helloworld"

# Replace the image reference with our published image.
perl -pi -e "s@github.com/knative/serving/sample/helloworld@${REPO}/sample/helloworld@g" sample/helloworld/*.yaml

# Deploy the Knative Serving sample
kubectl apply -f sample/helloworld/sample.yaml

Exploring

Once deployed, you can inspect the created resources with kubectl commands:

# This will show the route that we created:
kubectl get route -o yaml

# This will show the configuration that we created:
kubectl get configurations -o yaml

# This will show the Revision that was created by our configuration:
kubectl get revisions -o yaml

To access this service via curl, we first need to determine its ingress address:

watch kubectl get ingress

When the ingress is ready, you'll see an IP address in the ADDRESS field:

NAME                                 HOSTS                     ADDRESS   PORTS     AGE
route-example-ela-ingress   demo.myhost.net             80        14s

Once the ADDRESS gets assigned to the cluster, you can run:

# Put the Ingress Host name into an environment variable.
export SERVICE_HOST=`kubectl get route route-example -o jsonpath="{.status.domain}"`

# Put the Ingress IP into an environment variable.
export SERVICE_IP=`kubectl get ingress route-example-ela-ingress -o jsonpath="{.status.loadBalancer.ingress[*]['ip']}"`

If your cluster is running outside a cloud provider (for example on Minikube), your ingress will never get an address. In that case, use the istio hostIP and nodePort as the service IP:

export SERVICE_IP=$(kubectl get po -l istio=ingress -n istio-system -o 'jsonpath={.items[0].status.hostIP}'):$(kubectl get svc istio-ingress -n istio-system -o 'jsonpath={.spec.ports[?(@.port==80)].nodePort}')

Now curl the service IP as if DNS were properly configured:

curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}
# Hello World: shiniestnewestversion!

Updating

You can update this to a new version. For example, update it with a new configuration.yaml via:

kubectl apply -f sample/helloworld/updated_configuration.yaml

Once deployed, traffic will shift to the new revision automatically. You can verify the new version by checking route status:

# This will show the route that we created:
kubectl get route -o yaml

Or curling the service:

curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}
# Hello World: nextversion!

Manual traffic splitting

You can manually split traffic to specific revisions. Get your revisions names via:

kubectl get revisions

NAME                                     AGE
p-1552447d-0690-4b15-96c9-f085e310e98d   22m
p-30e6a938-b28b-4d5e-a791-2cb5fe016d74   10m

Update traffic part in sample/helloworld/sample.yaml as:

traffic:
  - revisionName: <YOUR_FIRST_REVISION_NAME>
    percent: 50
  - revisionName: <YOUR_SECOND_REVISION_NAME>
    percent: 50

Then update your change via:

kubectl apply -f sample/helloworld/sample.yaml

Once updated, you can verify the traffic splitting by looking at route status and/or curling the service.

Cleaning up

To clean up the sample service:

kubectl delete -f sample/helloworld/sample.yaml