Getting started with knative

This post is based on https://github.com/knative/docs/blob/master/install/getting-started-knative-app.md

This post uses the Hello World sample app in Go to demonstrate the basic workflow for deploying an app.

Install knative

Following the instructions at https://github.com/knative/docs/blob/master/install/Knative-with-any-k8s.md

Install Istio

Try to install Istio using the following command:

kubectl apply --filename https://github.com/knative/serving/releases/download/v0.4.0/istio-crds.yaml && \
kubectl apply --filename https://github.com/knative/serving/releases/download/v0.4.0/istio.yaml

You will probably see the error:

The Service "istio-ingressgateway" is invalid: spec.ports[0].nodePort: Invalid value: 31380: provided port is not in the valid range. The range of valid ports is 32768-35535

You need to download the https://github.com/knative/serving/releases/download/v0.4.0/istio-crds.yaml file locally and modify the ports used, to fall within this range:

Change the nodePort values from 31380, 31390, 31400 to 33380, 33390, 33400:

...
apiVersion: v1
kind: Service
metadata:
  name: istio-ingressgateway
  namespace: istio-system
  annotations:
  labels:
    chart: gateways-1.0.1
    release: RELEASE-NAME
    heritage: Tiller
    app: istio-ingressgateway
    istio: ingressgateway
spec:
  type: LoadBalancer
  selector:
    app: istio-ingressgateway
    istio: ingressgateway
  ports:
    -
      name: http2
      nodePort: 31380
      port: 80
      targetPort: 80
    -
      name: https
      nodePort: 31390
      port: 443
    -
      name: tcp
      nodePort: 31400
      port: 31400
....

to:

...
apiVersion: v1
kind: Service
metadata:
  name: istio-ingressgateway
  namespace: istio-system
  annotations:
  labels:
    chart: gateways-1.0.1
    release: RELEASE-NAME
    heritage: Tiller
    app: istio-ingressgateway
    istio: ingressgateway
spec:
  type: LoadBalancer
  selector:
    app: istio-ingressgateway
    istio: ingressgateway
  ports:
    -
      name: http2
      nodePort: 33380
      port: 80
      targetPort: 80
    -
      name: https
      nodePort: 33390
      port: 443
    -
      name: tcp
      nodePort: 33400
      port: 31400
...

Re-apply, using the modified local file:

kubectl apply --filename istio.yaml

Label the default namespace with istio-injection=enabled:

# kubectl label namespace default istio-injection=enabled

Monitor the Istio components until all of the components show a STATUS of Running or Completed:

# kubectl get pods --namespace istio-system

Install knative and dependencies

kubectl apply --filename https://github.com/knative/serving/releases/download/v0.4.0/serving.yaml \
--filename https://github.com/knative/build/releases/download/v0.4.0/build.yaml \
--filename https://github.com/knative/eventing/releases/download/v0.4.0/release.yaml \
--filename https://github.com/knative/eventing-sources/releases/download/v0.4.0/release.yaml \
--filename https://github.com/knative/serving/releases/download/v0.4.0/monitoring.yaml \
--filename https://raw.githubusercontent.com/knative/serving/v0.4.0/third_party/config/build/clusterrole.yaml

If you see an error such as:

unable to recognize "https://github.com/knative/eventing/releases/download/v0.4.0/release.yaml": no matches for kind "ClusterChannelProvisioner" in version "eventing.knative.dev/v1alpha1"
unable to recognize "https://github.com/knative/eventing/releases/download/v0.4.0/release.yaml": no matches for kind "ClusterChannelProvisioner" in version "eventing.knative.dev/v1alpha1"

you may be hitting a known issue:

https://github.com/knative/eventing/issues/680

It fails the first time because the `ClusterChannelProvisioner` CRD hasn't been fully reconciled yet when the in-memory-channel provisioner is created. The second time usually succeeds (because the CRD has been reconciled by then).

Simply re-run the command a second time to re-apply the same files.

Monitor the Knative components until all of the components show a STATUS of Running:

kubectl get pods --namespace knative-serving
kubectl get pods --namespace knative-build
kubectl get pods --namespace knative-eventing
kubectl get pods --namespace knative-sources
kubectl get pods --namespace knative-monitoring

Deploying your serverless app

To deploy an app using Knative, you need a configuration .yaml file that defines a Service.

This configuration file specifies metadata about the application, points to the hosted image of the app for deployment, and allows the deployment to be configured.

Create a new file named service.yaml with the following content:

# cat service.yaml

apiVersion: serving.knative.dev/v1alpha1 # Current version of Knative
kind: Service
metadata:
  name: helloworld-go # The name of the app
  namespace: default # The namespace the app will use
spec:
  runLatest:
    configuration:
      revisionTemplate:
        spec:
          container:
            image: gcr.io/knative-samples/helloworld-go # The URL to the image of the app
            env:
              - name: TARGET # The environment variable printed out by the sample app
                value: "Go Sample v1"

From the directory where the new service.yaml file was created, apply the configuration:

# kubectl apply --filename service.yaml

service.serving.knative.dev/helloworld-go created

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

Create a new immutable revision for this version of the app.
Perform network programming to create a route, ingress, service, and load balancer for your app.
Automatically scale your pods up and down based on traffic, including to zero active pods.

Interacting with your app

To see if your app has been deployed succesfully, you need the host URL and IP address created by Knative.

Use kubectl get svc to see the details of the service:

[root@hpe-ansible knative]# kubectl get svc istio-ingressgateway --namespace istio-system
NAME                   TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)                                                                                                                   AGE
istio-ingressgateway   LoadBalancer   10.96.72.109   <pending>     80:33380/TCP,443:33390/TCP,31400:33400/TCP,15011:33994/TCP,8060:34944/TCP,853:35094/TCP,15030:33326/TCP,15031:34179/TCP   1h

Patch the type to be NodePort:

# kubectl -n istio-system patch svc istio-ingressgateway --type='json' -p '[{"op":"replace","path":"/spec/type","value":"NodePort"}]'

service/istio-ingressgateway patched

And patch the port to be, for example, 33333:

# kubectl -n istio-system patch svc istio-ingressgateway --type='json' -p '[{"op": "add", "path":"/spec/ports/0/nodePort", "value":33333}]'

service/istio-ingressgateway patched

Check that the changes to the service have been made:

# kubectl get svc istio-ingressgateway --namespace istio-system -o yaml

Test service

To find the host URL for your service, enter:

# kubectl get ksvc helloworld-go  --output=custom-columns=NAME:.metadata.name,DOMAIN:.status.domain

NAME                DOMAIN
helloworld-go       helloworld-go.default.example.com

Simply use curl to test the service, specifing the appropriate port and domain:

# curl -vH "Host: helloworld-go.default.example.com" http://hpe2-ucp01.am2.cloudra.local:33333

Hello Go Sample v1!

Teardown

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

# kubectl delete --filename service.yaml

# Getting started with knative

# Install knative

# Install Istio

# Install knative and dependencies

# Deploying your serverless app

# Interacting with your app

# Test service

# Teardown