Managing Topics

On this section you will learn how to create, list, delete topics within your Kafka cluster

What is a Topic ?

A topic is described as a Stream of messages of a particular type. For example:

• Debit Transactions

• Credit Transactions

Topics are broken down one level more of granularity, they are formed by partitions.

Messages are written to it in an append-only fashion, and are read in order from beginning to end. There are no guarantee of ordering in a topic, but there is guarantee of ordering on the partition

Anatomy of a Topic

Docker hint

To start working with your cli, enter to the docker container by executing the following commands

docker ps | grep wurstmeister/kafka
docker exec -it [container_name] bash

From you bin folder, there is an script called kafka-topics.sh or kafka-topics.bat , and it will facilitate for you the creation of a Topic in your cluster

Go ahead and explore the options available for working with Topics via CLI

Kafka Topics Help

./kafka-topics.sh --help

Create a Topic

Now that you have explored a bit the command line, go ahead and create a topic with the following conditions:

• Topic name: wwcode

• Number of Partitions: 2

• Replicas: 1

Hint

./kafka-topics.sh --create ....

Bonus exercise

Try to create the same topic only if it doesn't exist.

List a Topic

When working with Kafka, you are most likely curious to see what is going on with your topic, if It was already created/updated/deleted, if the replicas are in sync or what is the partition leader.

Go ahead and list your topics by executing:

./kafka-topics.sh --list --zookeeper localhost:2181

Info

When listing your topics, we need to provide the zookeeper list, since Zookeeper is the one who keeps a record of the topics and Kafka underneath goes and query zookeeper to retrieve the topics for your cluster.

Bonus Exercise

Try to gather a full detailed description of the topic, specifically retrieve, PartitionCount, ReplicationFactor, and ISR ( In Sync Replicas)

Delete a Topic ( Danger )

There might be cases when you would like to delete a Topic. For example, there is type of event that will be retired from your application and you would like to delete this topic to avoid writing to a topic that won't be used anymore.

Go ahead and try to delete the topic you just have created before.

Bonus Exercise

Try to delete a topic that does not exist and see what happens. How you could solve this issue?