rest-api-go

Creating a RESTful Service

This sample demonstrates creating a simple RESTful service. The exposed endpoint takes a stock ticker (i.e. stock symbol), then outputs the stock price. The endpoint resource name is defined by an environment variable set in the configuration file.

Prerequisites

1. A Kubernetes cluster with Knative Serving installed.
2. Install Docker.
3. You need to configure outbound network access because this application makes an external API request.
4. Check out the code:

go get -d github.com/knative/docs/serving/samples/rest-api-go

Setup

Build the application container and publish it to a container registry:

1. Move into the sample directory:

cd $GOPATH/src/github.com/knative/docs

2. Set your preferred container registry:

export REPO="gcr.io/<YOUR_PROJECT_ID>"

To run the sample, you need to have a Google Cloud Platform project, and you also need to enable the Google Container Registry API.

3. Use Docker to build your application container:

docker build \
  --tag "${REPO}/serving/samples/rest-api-go" \
  --file serving/samples/rest-api-go/Dockerfile .

4. Push your container to a container registry:

docker push "${REPO}/serving/samples/rest-api-go"

5. Replace the image reference path with our published image path in the configuration files (serving/samples/rest-api-go/sample.yaml:

   • Manually replace:
     image: github.com/knative/docs/serving/samples/rest-api-go with image: <YOUR_CONTAINER_REGISTRY>/serving/samples/rest-api-go

   Or

   • Use run this command:

   perl -pi -e "s@github.com/knative/docs@${REPO}@g" serving/samples/rest-api-go/sample.yaml
   

Deploy the Configuration

Deploy the Knative Serving sample:

kubectl apply --filename serving/samples/rest-api-go/sample.yaml

Explore the Configuration

Inspect the created resources with the kubectl commands:

• View the created Route resource:

kubectl get route --output yaml

• View the created Configuration resource:

kubectl get configurations --output yaml

• View the Revision that was created by our Configuration:

kubectl get revisions --output yaml

Access the Service

To access this service via curl, you need to determine its ingress address.

1. To determine if your service is ready:

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

When the service is ready, you'll see an IP address in the EXTERNAL-IP field:

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

2. When the service is ready, export the ingress hostname and IP as environment variables:

export SERVICE_HOST=`kubectl get route stock-route-example --output jsonpath="{.status.domain}"`
export SERVICE_IP=`kubectl get svc knative-ingressgateway --namespace istio-system \
--output jsonpath="{.status.loadBalancer.ingress[*].ip}"`

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

export SERVICE_IP=$(kubectl get po --selector knative=ingressgateway --namespace istio-system \
  --output 'jsonpath={.items[0].status.hostIP}'):$(kubectl get svc knative-ingressgateway --namespace istio-system \
  --output 'jsonpath={.spec.ports[?(@.port==80)].nodePort}')

3. Now use curl to make a request to the service:

• Make a request to the index endpoint:

curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}

Response body: Welcome to the stock app!

• Make a request to the /stock endpoint:

curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}/stock

Response body: stock ticker not found!, require /stock/{ticker}

• Make a request to the /stock endpoint with a ticker parameter:

curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}/stock/<ticker>

Response body: stock price for ticker <ticker> is <price>

Clean Up

To clean up the sample service:

kubectl delete --filename serving/samples/rest-api-go/sample.yaml