Knative

abstracting away the complex details and enabling developers to focus on what matters

Enterprise-grade Serverless on your own terms. Kubernetes-based platform to deploy and manage modern serverless workloads.

Components

1. Serving
2. Eventing

Concept

Serving Resources

1. Service: The service.serving.knative.dev resource automatically manages the whole lifecycle of your workload. It controls the creation of other objects to ensure that your app has a route, a configuration, and a new revision for each update of the service. Service can be defined to always route traffic to the latest revision or to a pinned revision.
2. Route: The route.serving.knative.dev resource maps a network endpoint to one or more revisions. You can manage the traffic in several ways, including fractional traffic and named routes.
3. Configuration: The configuration.serving.knative.dev resource maintains the desired state for your deployment. It provides a clean separation between code and configuration and follows the Twelve-Factor App methodology. Modifying a configuration creates a new revision.
4. Revision: The revision.serving.knative.dev resource is a point-in-time snapshot of the code and configuration for each modification made to the workload. Revisions are immutable objects and can be retained for as long as useful. Knative Serving Revisions can be automatically scaled up and down according to incoming traffic. See Configuring the Autoscaler for more information.

Getting Started

1. Install Knative CLI kn.

   For Mac:

   brew install kn
   

2. Install the Knative "Quickstart" plugin. (kn CLI's plugin.)

   ※ Somehow brew fails.

   brew install knative-sandbox/kn-plugins/quickstart
   

   -> Follow this

   1. Download the binary
   2. Move it to /usr/local/bin

      mv ~/Downloads/kn-quickstart-darwin-amd64 /usr/local/bin/kn-quickstart
      chmod +x /usr/local/bin/kn-quickstart
      

   3. Check plugin.

      kn plugin list
      - kn-quickstart : /usr/local/bin/kn-quickstart
      

   kn quickstart kind
   

   pods

   kubectl get po -A
   NAMESPACE            NAME                                            READY   STATUS    RESTARTS   AGE
   knative-eventing     eventing-controller-58875c5478-bhhcd            1/1     Running   0          56s
   knative-eventing     eventing-webhook-5968f79978-cswb4               1/1     Running   0          56s
   knative-eventing     imc-controller-86cd7b7857-ndx69                 1/1     Running   0          41s
   knative-eventing     imc-dispatcher-7fcb4b5d8c-rtjkz                 1/1     Running   0          41s
   knative-eventing     mt-broker-controller-8d979648f-nv4w4            1/1     Running   0          27s
   knative-eventing     mt-broker-filter-574dc4457f-x4lch               1/1     Running   0          27s
   knative-eventing     mt-broker-ingress-5ddd6f8b5d-llj4g              1/1     Running   0          27s
   knative-serving      activator-85bd4ddcbb-sdgkc                      1/1     Running   0          2m14s
   knative-serving      autoscaler-84fcdc5449-52rzj                     1/1     Running   0          2m14s
   knative-serving      controller-6fd5bb86df-zctsm                     1/1     Running   0          2m14s
   knative-serving      domain-mapping-74d5d688bd-k9stl                 1/1     Running   0          2m14s
   knative-serving      domainmapping-webhook-8484d5fd8b-6jb9n          1/1     Running   0          2m14s
   knative-serving      net-kourier-controller-66bc9d6697-czjbr         1/1     Running   0          97s
   knative-serving      webhook-97c648588-rwb6n                         1/1     Running   0          2m13s
   kourier-system       3scale-kourier-gateway-58856c6cc7-czpnz         1/1     Running   0          97s
   kube-system          coredns-78fcd69978-qdg6m                        1/1     Running   0          2m28s
   kube-system          coredns-78fcd69978-qj7xh                        1/1     Running   0          2m28s
   kube-system          etcd-knative-control-plane                      1/1     Running   0          2m43s
   kube-system          kindnet-h85z6                                   1/1     Running   0          2m28s
   kube-system          kube-apiserver-knative-control-plane            1/1     Running   0          2m42s
   kube-system          kube-controller-manager-knative-control-plane   1/1     Running   0          2m43s
   kube-system          kube-proxy-b9p56                                1/1     Running   0          2m28s
   kube-system          kube-scheduler-knative-control-plane            1/1     Running   0          2m43s
   local-path-storage   local-path-provisioner-85494db59d-99nt7         1/1     Running   0          2m28s
   

3. Apply hello.yaml

   kubectl apply -f hello.yaml
   

4. Check

   Knative service:

   kn service list
   

   NAME    URL                                LATEST   AGE   CONDITIONS   READY     REASON
   hello   http://hello.default.example.com            36s   0 OK / 3     Unknown   RevisionMissing : Configuration "hello" is waiting for a Revision to become ready.
   

   kn service list
   NAME    URL                                LATEST        AGE   CONDITIONS   READY   REASON
   hello   http://hello.default.example.com   hello-world   37m   3 OK / 3     True
   

   Check Hello World.

   curl http://hello.default.127.0.0.1.sslip.io
   
   Hello World!
   

5. Scaling to Zero

   It may take up to 2 minutes for your Pods to scale down. Pinging your service again will reset this timer.

   kubectl get pod -l serving.knative.dev/service=hello
   No resources found in default namespace.
   

6. Basics of Traffic Splitting

   1. Creating a new Revision

      kn service update hello \
      --env TARGET=Knative \
      --revision-name=knative
      

      Updating Service 'hello' in namespace 'default':
      
        0.024s The Configuration is still working to reflect the latest desired specification.
        3.181s Traffic is not yet migrated to the latest revision.
        3.210s Ingress has not yet been reconciled.
        3.242s Waiting for load balancer to be ready
        3.419s Ready to serve.
      
      Service 'hello' updated to latest revision 'hello-knative' is available at URL:
      http://hello.default.127.0.0.1.sslip.io
      

   2. Check

      curl http://hello.default.127.0.0.1.sslip.io
      Hello Knative!
      

   3. Splitting Traffic

      kn revisions list
      
      NAME            SERVICE   TRAFFIC   TAGS   GENERATION   AGE     CONDITIONS   READY           REASON
      hello-knative   hello     100%             2            2m12s   3 OK / 4     True
      hello-world     hello                      1            120m    3 OK / 4     True
      

      kn service update hello \
      --traffic hello-world=50 \
      --traffic @latest=50
      

      kn revisions list
      
      NAME            SERVICE   TRAFFIC   TAGS   GENERATION   AGE    CONDITIONS   READY   REASON
      hello-knative   hello     50%              2            3m1s   3 OK / 4     True
      hello-world     hello     50%              1            121m   3 OK / 4     True
      

   4. Check

      ± curl http://hello.default.127.0.0.1.sslip.io
      Hello Knative!
      
      ± curl http://hello.default.127.0.0.1.sslip.io
      Hello Knative!
      
      ± curl http://hello.default.127.0.0.1.sslip.io
      Hello Knative!
      
      ± curl http://hello.default.127.0.0.1.sslip.io
      Hello World!
      

7. Clean up

   kn service delete hello
   

8. Clean up cluster

   kind delete clusters knative