Praktikumsblatt 9 - Serverless Computing (Richard Clauss)

 

Task 1 - Definition of serverless computing

How can serverless computing be defined and how can it be distinguished from a kubernetes based PaaS offering?

 

Task 2 - Install knative on your kubernetes cluster

Recommendation: Use minikube or kind to be able to use kn's quickstart plugin

1. Install knative on your kubernetes cluster.
2. Create a knative service with a webapp of your choice and request it by using an http-client.

 

Task 3 - Cold-start-delay

1. Describe the cases in which a cold-start-delay can occur.
2. Create a service in knative that uses the standard knative pod autoscaler and for which the occurrence of cold-start-delays is impossible.
3. Wait one minute to simulate that the service didn't receive any traffic for one minute. Verify that no cold start occurs when sending a request to the service.

 

Task 4 - Revisions and Traffic Splitting

1. Create a knative service responding with http status code 200 to all http GET requests
2. Create a new revision of this knative service, which responds with http status code 201 to all http GET requests
3. Let knative split the incoming traffic 40% to the first revision and 60% to the second revision
4. Test the traffic splitting functionality by using a load generator. (For example, use the tool "hey")

 

Task 5 - Autoscaling

1. Create a knative service with a target concurrency of 10 concurrent requests per replica. Use the default Knative Pod Autoscaler.
2. Let the new service receive 50 concurrent http-requests from a load generator (for example use the tool "hey").
3. You will see that the autoscaling algorithm does not scale the number of replicas to exactly 5 as expected. How many replicas do you see?
4. Describe the reason for the observed behavior and change the configuration so that you see exactly 5 replicas for 50 concurrent requests.

 

Task 6 - Domains

1. Configure that requesting the domain stable.example.de via knative's ingress forwards traffic to the service from task 4 (no https needed)
2. Verify the correct functionality of the domain mapping with an http-client.

 

Task 7 - Knative Eventing

1.  Create a new knative eventing broker, which has the type "Multi-tenant channel-based broker"
2. Create a trigger listening for events on the new broker, which forwards CloudEvents to one of your already created knative services.
   The trigger shall only react to CloudEvents having a type with a value of your choice
3. Verify the correct functionality of the trigger by sending a CloudEvent to your broker.
   (You need to send the event from a pod inside the kubernetes cluster to reach the broker url, or you will get http status code 404 from the ingress controller. I recommend using curl to send a simple event from a pod within the cluster)