By mabulgu August 25, 2020

Strimzi Kafka CLI: Managing Strimzi in a Kafka Native Way

Apache Kafka today, is a popular distributed streaming technology providing pub/sub mechanism, storing, and processing streams in a distributed way.

As Kubernetes becomes more and more popular day by day, it is inevitable for a technology like Apache Kafka to run on Kubernetes platform natively. Using some capabilities of Kubernetes like Operator Framework or Statefulsets, a group of people from Red Hat, started an open-source community project called Strimzi which is one of the most popular and reliable Kubernetes operators as a CNCF sandbox project.

It has been almost a year since I gave a speech about Strimzi with the topic “Strimzi: Distributed Streaming with Apache Kafka in Kubernetes” at Istanbul JUG community. Since then a lot has been changed both in the Apache Kafka and the Strimzi world. Zookeeper has now TLS support, and Strimzi is improved with many features like SCRAM-SHA authentication, MirrorMaker2, and many more. Strimzi is more powerful now and this -as the upstream project- is what makes Red Hat AMQ Streams stronger.

Besides many features and improvements on Strimzi aka. (Strimzi Kafka Operator), today I want to introduce you to a tool that I’ve been working on for a while, aiming of making traditional Apache Kafka administrators’ or developers’ life easier while using Kubernetes-Cloud Native Kafka: Strimzi. But before that, let me tell you my short story about meeting with Kafka and Strimzi and experiences afterward. Don’t worry, we will come to a point:)

Meeting Apache Kafka

It was a few years ago I was working as a developer at sahibinden.com a classified ad and e-commerce company. At Sahibinden, we welcomed very high numbers of concurrent visitors at that time including the ones who are not logged in. One of the biggest challenges was actually this because one can surf through all the site content anonymously and do any actions with the classified ads, and other components by viewing details, clicking, etc. And my Apache Kafka journey began with one of those challenges.

The job was: each classified ad visit had to be saved to a list that had to be created for each user -including the anonymous ones- as Last Visited Classified Ads. Before that project, I had no idea of any messaging technology, and its usage or their differences. Kafka had been used for a time in the company and architects had already decided what technology to use for that kind of project. So by getting the basic info and discussing the architecture with the fellow architects I started the project. I won’t go in details but the structure was roughly this: when a user visits a classified ad, put it into a Kafka topic, then consume it to save it into MongoDB database. Easy-peasy!

I made the first implementation. The code is reviewed, and released with the next release and BOOM! The guy form the architect/system team came to me and said something like “consumer lag”. What the hell was this consumer lag?!

I went with him to his desk to see what is happening and he wrote a couple of commands starting with “kafka-consumer-groups” and show me the offset difference for each partition per topic. I knew what a topic was but what was a partition? Did I use an ID for data consistency? What? The guy was talking like in a language that I’d never heard of.

Yeah, I have to admit that since all the code structure was ready and thought Kafka as a simple message broker without thinking about its distributed structure, I did not even move a finger to know more about Kafka itself. Anyways, the status was bad and since MongoDB could not handle too many upserts in a queue that comes from the Kafka consumers, the producer could produce data -because visitors kept visiting classified ads- but the consumer could not consume after some time because of the non-responding MongoDB.

For the “how did we solve this?” part which is not too much important for this article: We put the data to the cache, while producing it for Kafka, saved the data in bulks for each consume, and did upserts in bulks to MongoDB. And a few tweaks like changing the data retention time later.

Importance of a CLI

However, the reason behind I wanted to share with you this short story is not the solution. Apart from its being a system design problem that had to be solved, I just wanted you to notice -even if you are a very experienced person about Kafka itself- administrating and monitoring Apache Kafka is important and it has the very basic and easy to use tools bundled in itself. I am not talking about the detailed monitoring but mostly the administration itself because with just one command, having just Kafka binaries and its other relevant files itself you can do anything allowed in the whole Kafka cluster.

There are of course many tools that help people with the administration of Kafka, but it all starts with setting up the cluster and creating maybe a few topics with commands (actually sh files) that Apache Kafka provides or adding ACLs, changing topic configurations, etc. via Command Line Interface (CLI). CLIs always have been the simplest approach that holds the procedural benefits of the administration world. For the example I gave you, consumer lag check or the topic configuration changes like “log.retention.ms” were done via CLI at that time because it was the simplest, and most reliable approach while everything was on fire!

The AMQ Streams Journey

After my first interaction and stormy experience with Kafka, I did not do anything with it since I had my AMQ Streams on RHEL engagement for a customer in Red Hat, this time not as a developer, but as a consultant. That time -it has been about 1.5 years- Red Hat has this brand-new product called AMQ Streams which provided (and still provides) an enterprise-level Apache Kafka support both in RHEL (bare metal or VM) and its enterprise-level Kubernetes platform: OpenShift. While AMQ Streams on RHEL is the pure Apache Kafka that is hardened, extended, and versioned by Red Hat with full support, AMQ Streams on OpenShift is nothing but the Strimzi project which become a CNCF sandbox project in a short time successfully.

I don’t want to make a branch of this topic and steer to another one by talking about the preparation phase for the customer engagement which was tough but shortly I have to say that I learned all Kafka stuff starting with creating a topic, continuing with administration, security, and monitoring lastly in just one week! It was fun and challenging. The first phase of my customer engagement took about one week or two. It was an important customer who wanted Apache Kafka capabilities supported by a strong vendor like Red Hat because the project was a very important and vital government project.

We finished the project successfully, a couple of problems occurred when I was in London for training, but thanks to the time difference between London and Istanbul I was lucky to have a couple of extra times to discuss and solve the issue with the help of my colleagues from the support team and our Kafka and Strimzi hero Jakub Scholz from the Kafka/Strimzi engineering team.

At the end of the engagement -including the preparation phase- I -for the second time- realized Apache Kafka is a middleware that has a strong binary set as CLI that you can use both for setting up the cluster and topics, and most importantly for day-two operations.

Strimzi in Action

While playing with AMQ Streams and Kafka -because I am not only a middleware consultant but also a so-called “AppDev” consultant whose playground is OpenShift- Strimzi got my attention and started to play with it, and fall in love with it and the idea behind it: running Apache Kafka on a Kubernetes platform natively!

It used the Operator Framework which was pretty new for the Red Hat Middleware world back then (because I remember doing stuff with i.e. Infinispan/Data Grid with OpenShift templates even if there is Operator Framework. Gosh, what a struggle that was..!). The operator(s) for Strimzi managed the Kubernetes custom-resources for Kafka cluster itself, users, topics, mirroring, Kafka Connect, etc. which were bare YAML definitions. It was true magic! I had to learn about this, and I had to talk about this; show this to people. So I got my invitation from my fellows from Istanbul JUG, and did a talk about “Strimzi: Distributed Streaming with Apache Kafka in Kubernetes“. It took a little bit long but it was all fun, because most of the audience stayed till the end, and did some mind-bending conversations about messaging and Kafka.

I had this demo part at the end and while doing the demo, I realized as a traditional Apache Kafka user -which that time I could call myself so because had some real-time hands-on experience so far- changing the YAML file for a specific custom-resource for a specific configuration (for example a topic configuration) and calling oc or kubectl apply -f with that YAML file felt like it’s not accessing to Kafka or it’s not Kafka, but its something else, something different.

DevOps Transformation

Because I had been doing stuff around OpenShift AppDev and CI/CD, creating resources or custom-resources for OpenShift applications or components was not a new thing for me. But from a Kafka admin’s perspective it may be pretty hard in the first place because you both want her/him to focus on both the middleware and the platform.

As a consultant and supervisor for customers, I mostly propose the customers I work with to break down the silos by starting with the person(s) first which means: don’t say “this is not part of my business, I can not do OpenShift, Kubernetes, etc. while writing Java, Python, etc. code or dealing with middleware”. Well since infrastructure, middleware and application are closer now -because of the Cloud/Kubernetes Native Era- people who create or manage them should be more closer, which is a reflection of DevOps culture and change and this should start from personal sentience and responsibility. So in short, a Kafka administrator should learn about Openshift or Kubernetes if her/his company started to use Strimzi. She/he should learn about “kubectl” or “oc”, should learn about how a Kubernetes platform works or the Operator Framework.

Or even further, she/he should learn about GitOps (we will visit this topic later again for Strimzi:) ), writing and dealing with YAMLs, or a source control system like git. Isn’t this too much? Or is there any company that could do this DevOps transformation like a finger snap of Thanos?

DevOps transformation is tough because it is (and must be) a cultural transformation and has to start with peopleor even person-, then process, and lastly technology which most of the companies prefer to start with.

I remember a couple of customers who already implemented most of the DevOps practices but has still huge silos that are hard to break because of the organizational structure -because of the cultural structure. I remember the begging eyes of the Kafka admins or developers while we were doing a meeting about AMQ Streams on Openshift (Strimzi) asking like “isn’t there any other way to do this like traditional Kafka?” in the meetings.

Using the classic Kafka shell binaries for accessing the Strimzi Kafka cluster, of course, partially possible. But as I’ve said “partially”, the best practice to manage Strimzi is to use its custom resources and the operator framework, because this is the way to manage it in a Kubernetes Native way which is the main intention. This is not a classic “best-practice” case, because some parts of Strimzi (for example ACLs), doesn’t support two-way binding intentionally by design and architecture. So accessing to Strimzi Kafka cluster with a Kubernetes native way is vital.

Well, besides its being a part of the “transformation” to DevOps even if it is in reverse order (technology-> process-> people), I felt like these folks need a kind of “ferry” that they can use while building a “bridge” between the traditional middleware coast to Cloud Native and DevOps coast, which needs time to build because -as I’ve said again and again- it is a cultural change in the core.

Idea of a CLI for Strimzi

It was actually about 6 months ago. While I was preparing this workshop, CI/CD with Tekton in a Multi-cluster OpenShift Environment, I was surprised to see that Tekton could be both managed via custom resource definition YAMLs (kubectl/oc apply -f), or one could just use the Tekton CLI (tkn) to create, manipulate any object of Tekton itself; both would be handled by the Tekton’s operator.

So the idea evolved in my mind: why not use the same strategy for Strimzi too, and create an interface -actually, a command-line interface- which has the intention of helping traditional Kafka users (administrators, developers, system engineers) by providing a user experience that Apache Kafka has in terms of command executables that we talked about before.

A ferry ready to use, before building the bridge (or for those who don’t have any intention to build one).

For keeping everything Kubernetes/OpenShift Native and providing Strimzi/AMQ Streams users the closest and most familiar experience for accessing and managing Kafka, I started an open-source project that provides a command-line interface which creates/manipulates Strimzi custom-resources and applies them by using -very mostly- familiar parameters of traditional Kafka commands.

And I named the project Strimzi Kafka CLI.

With Strimzi Kafka CLI, you can create, alter, delete topics, users, manage ACLs, create, and change the configuration of the Kafka cluster, topics, users. Most importantly, you can most of these -with a few differences and additions- just like you do with Kafka shell files. Let’s see an example:

For example to create a Kafka topic with name “messages” let’s say with 24 partitions and 3 replication factors you would normally write this command:

bin/kafka-topics.sh --create --topic messages --partitions 24 --replication-factor 3 --zookeeper [zk_ip_here]:2181

It’s pretty much the same with the Strimzi Kafka CLI:

kfk topics --create --topic messages --partitions 24 --replication-factor 3 -c [strimzi_kafka_cluster_name] -n [kubernetes_namespace_for_cluster]

Please notice that the “kafka-topics.sh” command is transformed to a similar command for Strimzi as “kfk” with the “topics” option which creates the “kfk topics” command together.

Inspired by the CLI of the Tekton project, I wanted to use a three-letter main command both for which will not be hard to remember -like Tekton’s tkn– and will evoke the usage of “kafka-*.sh”.

Basically for the current version, which is 0.1.0-alpha25, the command options are like the following (We get it by running the “kfk –help” command):

kfk --help
Usage: kfk [OPTIONS] COMMAND [ARGS]...

  Strimzi Kafka CLI

Options:
  --help  Show this message and exit.

Commands:
  acls              This tool helps to manage ACLs on Kafka.
  clusters          The kafka cluster(s) to be created, altered or...
  configs           Add/Remove entity config for a topic, client, user or...
  console-consumer  The console consumer is a tool that reads data from...
  console-producer  The console producer is a tool that reads data from...
  topics            The kafka topic(s) to be created, altered or described.
  users             The kafka user(s) to be created, altered or described.
  version           Prints the version of Strimzi Kafka CLI

While having similar kinds of commands like acls, configs, console-consumer, console-producer, topics, Strimzi Kafka CLI has some additional commands like clusters, users for managing Strimzi custom resources directly, because of the concern of running the commands towards the Strimzi operator itself. I believe this will also improve the users’ adaptation of using Kafka that lives natively in Kubernetes/OpenShift context while writing the same kind of commands and almost similar options like Kafka binaries provide and learning a few objects’ management that belongs to Strimzi.

For example while one can both create an ACL for a current user with the following command which is more familiar for native Kafka users…:

kfk acls --add --allow-principal User:my-user --topic my-topic --operation describe -n kafka -c my-cluster

…the other may prefer to directly alter the user for changing its ACLs:

kfk users --alter --user my-user --add-acl --resource-type topic --resource-name my-topic --operation describe -c my-cluster -n kafka

Both commands will add the ACL to user “my-user” for the topic “my-topic” in the same way: by changing the User custom resource of Strimzi.

Strimzi Kafka CLI uses YAML examples from the original package of Strimzi, so each Strimzi Kafka CLI version uses a relevant version -usually, the latest one which is currently 0.19.0- of the Strimzi custom resource files.

Apart from this, as a dependency, Strimzi Kafka CLI uses the latest version of the kubectl binary that is downloaded regarding the operating system at the first usage. Strimzi Kafka CLI uses kubectl for accessing Kubernetes/OpenShift cluster(s) and for applying the relevant resources of Strimzi Kafka Operator.

To see the version of these external dependencies or the current version of Strimzi Kafka CLI which is being used following command should be used:

kfk version
CLI Version: 0.1.0a25
Strimzi Version: 0.19.0
Kubectl Version: v1.18.0

Strimzi Kafka CLI is currently in Alpha version since it is not feature-complete yet (but will probably be Beta in a short period of time; fingers crossed:) ).

For each version a PyPi release (since this is a Python project:) ) is created automatically -via Github actions- where anybody can install Strimzi Kafka CLI easily with pip command:

 pip install strimzi-kafka-cli

Each release creation also triggers a container image build which is tagged with the same version of the application for possible usages of using it in as a Tekton step, or any other container-native usage. Containerized versions of Strimzi Kafka CLI is located in quay.io and can be pulled with any container CLI:

docker pull quay.io/systemcraftsman/strimzi-kafka-cli:latest

or

podman pull quay.io/systemcraftsman/strimzi-kafka-cli:latest

So it is possible to get Strimzi Kafka CLI via PyPi as a binary package for direct usage or an image version of it in order to run it on in a container.

There are lots of things to tell here but I think the best way to explain something is not by telling it but by showing about it. Therefore I created this introductory video about Strimzi Kafka CLI which will be the start of a potential video series:

I hope Strimzi Kafka CLI will be useful for those who need a CLI approach to help them while being in their DevOps transformation journey and for those who want to try out a different approach.

And from an open-source developer’s perspective -and of course, as a proud Red Hatter-, I hope Strimzi community can benefit from this project at the end.

Either be a user of Strimzi Kafka CLI, or just a source-code viewer, please feel free to contribute to the project and improve it together.

So since this is about the end of the article, let’s finish it here with a memorable quote by Franz Kafka – the well-known author, whose name is given to Apache Kafka-, from one of his most famous book “The Metamorphosis”:

“As Gregor Samsa awoke one morning from uneasy dreams he found himself transformed in his bed into a gigantic insect.”

― Franz Kafka, The Metamorphosis

For me, it was first Apache Kafka. Then Kafka on Kubernetes with Strimzi. And the creation of a CLI for it. What a process of metamorphosis🙂

Take care👋

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mabulgu