Test new kafka streams application on K8S with prod data

Or how to pipe messages from one kafka cluster to another cluster through kubectl and your local machine

Aug 27 · 3 min read


Here is a typical situation in enterprises that recently took on streaming and kubernetes in their Big Data infrastructure: Two environments for production and testing, each with their own K8S cluster and their own MSK (kafka) cluster and a firewall in between. In our case, it’s all on AWS and you cannot reach the kafka clusters directly. Now the testing environment has a new version of an application installed but the prod data doesn’t get routed to that environment. How do you test the application with prod data?

We have 3 raw incoming streams from an on-premise environment that feeds our production kafka. I want to feed 10k messages of each stream into the test environment to see if everything works out as expected. We have a dashboard that shows the message streams of each of the three streams in prod and if everything looks clean, raw messages on the left lead to a lot of traffic in our egress. I’m aiming for the same case with our testing environment

plenty of traffic in prod
nothing yet in testing

Now some shell magic with kubectl kafka-console-consumer and kafka-console-producer . The core idea: tail -n 10000 kafka1:/topic{1,2,3} kafka2:/topic{1,2,3}

Pull data from kafka prod

For this, I deploy a small helper container

kubectl run -i --rm --tty kafka-helper --image="confluentinc/cp-kafka" --command "/bin/bash"

Now inside of this container, I execute some commands to collect messages.

mkdir messages
cd messages
kafka-console-consumer --bootstrap-server "$SERVER" --topic people-raw-v1 --from-beginning | head -n 10000 > people-raw-v1
kafka-console-consumer --bootstrap-server "$SERVER" --topic cars-raw-v1 --from-beginning | head -n 10000 > cars-raw-v1
kafka-console-consumer --bootstrap-server "$SERVER" --topic clicks-raw-v1 --from-beginning | head -n 10000 > clicks-raw-v1

This creates three files in /messages which we can now grab. In a new terminal window run the copy command

kubectl cp kafka-helper-977c4988d-p78gb:/messages ./messages

You will have to change the container name here. Check it with kubectl get pods .

Push data to kafka test

Now, connect to the different cluster. In my case, I have to update my kubeconfig for this so I run

aws eks update-kubeconfig --name clientx-datalake-eks-cluster-dev --region eu-central-1 --profile clientX-dev

Now my kubectl is linked to the new cluster. Same procedure as above, I

  1. create a new kafka-helper with an interactive shell
cd /messages
cat people-raw-1 | kafka-console-producer --broker-list "$SERVER" --topic people-raw-v1
cat cars-raw-1 | kafka-console-producer --broker-list "$SERVER" --topic cars-raw-v1
cat clicks-raw-v1 | kafka-console-producer --broker-list "$SERVER" --topic clicks-raw-v1

Et voilà:

All messages went through our flow and the results look good in our egress.


Run all of this in a single script from your machine. For this, you can use something like

kubectl run tail -i --rm --restart=Never --image=confluentinc/cp-kafka:5.1.2 -- <COMMAND_ON_POD> > file


Better data engineering


Written by

Software Developer, Tech enthusiast, student, board sports and food lover


Better data engineering

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade