> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Demo Topics Partitions and Brokers

> Guide to creating and inspecting Apache Kafka topics, configuring partitions and replication, and using Kafka CLI tools to view topic and broker metadata.

Hello, and welcome back.

In this lesson we’ll practice creating and inspecting Apache Kafka topics, configuring partitions and replication, and using the Kafka CLI tools to examine topic and broker metadata.

## Lab environment

This lab runs in the KodeKloud environment where Kafka is already installed. Start by navigating to the Kafka installation directory to locate the binaries you'll use:

```bash theme={null}
# change to the Kafka installation directory
cd /root/kafka

# list the top-level files
ls -l
```

The Kafka command-line scripts live in the `bin` directory. Change into `bin` to see helper scripts used for managing Kafka:

```bash theme={null}
cd /root/kafka/bin
ls -l
```

Example excerpt (truncated):

```text theme={null}
-rwxr-xr-x 1 root root   863 Sep 13  2022 kafka-topics.sh
-rwxr-xr-x 1 root root   895 Sep 13  2022 kafka-console-producer.sh
-rwxr-xr-x 1 root root   723 Sep 13  2022 kafka-console-consumer.sh
-rwxr-xr-x 1 root root  1010 Sep 13  2022 kafka-server-start.sh
...
```

## Quick reference: common Kafka CLI commands

| Purpose                    | Command example                                                                                                                        |
| -------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |
| Create or manage topics    | `./kafka-topics.sh --create --topic <name> --bootstrap-server localhost:9092`                                                          |
| Describe topic metadata    | `./kafka-topics.sh --describe --topic <name> --bootstrap-server localhost:9092`                                                        |
| Change topic config        | `./kafka-configs.sh --bootstrap-server localhost:9092 --entity-type topics --entity-name <name> --alter --add-config retention.ms=...` |
| Broker API versions & list | `./kafka-broker-api-versions.sh --bootstrap-server localhost:9092`                                                                     |

## Create a simple topic

Create a topic named `demo_topic` with the Kafka topics script:

```bash theme={null}
# create a topic named demo_topic
./kafka-topics.sh --create --topic demo_topic --bootstrap-server localhost:9092
```

What the flags mean:

* `--create` — create a new topic.
* `--topic demo_topic` — the topic name.
* `--bootstrap-server localhost:9092` — address of a broker to bootstrap against (replace with your cluster's bootstrap server(s)).

Typical response:

```bash theme={null}
WARNING: Due to limitations in metric names, topics with a period ('.') or underscore ('_') could collide. To avoid issues it is best to use either, but not both.
Created topic demo_topic.
```

You can also verify the newly created topic using a web UI such as `Kafdrop` or Confluent Control Center.

<Frame>
  <img src="https://mintcdn.com/kodekloud-c4ac6d9a/lPmuTD3Rx7FZuv6W/images/Event-Streaming-with-Kafka/Building-Blocks-of-Kafka/Demo-Topics-Partitions-and-Brokers/kafdrop-kafka-cluster-overview-screenshot.jpg?fit=max&auto=format&n=lPmuTD3Rx7FZuv6W&q=85&s=95355a673cbd55ee813158ddd0a22623" alt="The image is a screenshot of a Kafdrop interface showing a Kafka Cluster Overview, including details about bootstrap servers, brokers, and topics." width="1920" height="1080" data-path="images/Event-Streaming-with-Kafka/Building-Blocks-of-Kafka/Demo-Topics-Partitions-and-Brokers/kafdrop-kafka-cluster-overview-screenshot.jpg" />
</Frame>

Clicking the topic in the UI will display configuration and partition metadata.

## Create a topic with partitions and replication

Partitions increase throughput and parallelism by spreading data across brokers. Create a topic with three partitions and a replication factor of 1:

```bash theme={null}
./kafka-topics.sh --create --topic partitioned_topic --partitions 3 --replication-factor 1 --bootstrap-server localhost:9092
```

Best practices:

<Callout icon="lightbulb" color="#1CB2FE">
  Align partition counts to your throughput and consumer parallelism needs. More partitions can improve parallelism but add overhead for management, disk usage, and leader elections.
</Callout>

<Callout icon="warning" color="#FF6B6B">
  Replication factor must not exceed the number of available brokers. If you set `--replication-factor` greater than your broker count, topic creation will fail.
</Callout>

## Describe a topic (inspect metadata)

To view topic metadata—partition count, leader, replicas, in-sync replicas (ISR), and per-topic configs—use the `--describe` option:

```bash theme={null}
./kafka-topics.sh --describe --topic partitioned_topic --bootstrap-server localhost:9092
```

Sample output:

```bash theme={null}
Topic: partitioned_topic    TopicId: X8KJGSg5hThQHfo3DTm3eg    PartitionCount: 3    ReplicationFactor: 1    Configs: segment.bytes=1073741824
    Partition: 0    Leader: 1    Replicas: 1    Isr: 1
    Partition: 1    Leader: 1    Replicas: 1    Isr: 1
    Partition: 2    Leader: 1    Replicas: 1    Isr: 1
```

## Change topic configuration (retention example)

Topic-level configurations can be updated with `kafka-configs.sh`. For example, set retention to 2 days (milliseconds):

```bash theme={null}
# set retention to 2 days (in milliseconds)
./kafka-configs.sh --bootstrap-server localhost:9092 --entity-type topics --entity-name partitioned_topic --alter --add-config retention.ms=172800000
```

Expected response:

```bash theme={null}
Completed updating config for topic partitioned_topic.
```

Verify the change by re-describing the topic:

```bash theme={null}
./kafka-topics.sh --describe --topic partitioned_topic --bootstrap-server localhost:9092
```

Sample updated output showing `retention.ms`:

```bash theme={null}
Topic: partitioned_topic    TopicId: X8KJGSg5hThQHfo3DTm3eg    PartitionCount: 3    ReplicationFactor: 1    Configs: segment.bytes=1073741824,retention.ms=172800000
    Partition: 0    Leader: 1    Replicas: 1    Isr: 1
    Partition: 1    Leader: 1    Replicas: 1    Isr: 1
    Partition: 2    Leader: 1    Replicas: 1    Isr: 1
```

## Inspect broker API versions and broker list

To confirm broker identities and supported API versions (useful when troubleshooting compatibility or determining available features), run:

```bash theme={null}
./kafka-broker-api-versions.sh --bootstrap-server localhost:9092
```

Sample output (truncated):

```bash theme={null}
kafka-node:9092 (id: 1 rack: null) ->
    Produce(0): 0 to 9 [usable: 9],
    Fetch(1): 0 to 13 [usable: 13],
    ListOffsets(2): 0 to 7 [usable: 7],
    Metadata(3): 0 to 12 [usable: 12],
    LeaderAndIsr(4): 0 to 6 [usable: 6],
    ...
    CreatePartitions(37): 0 to 3 [usable: 3],
    DescribeCluster(60): 0 [usable: 0]
```

In this lab you have a single broker (sufficient for practicing topic creation and configuration changes). In production, use at least three brokers for fault tolerance and to support replication.

## Further reading and resources

* [Apache Kafka Documentation](https://kafka.apache.org/documentation/)
* [Kafdrop (open-source Kafka web UI)](https://github.com/obsidiandynamics/kafdrop)
* [Confluent Control Center](https://www.confluent.io/product/control-center)

That is it for this lesson. See you in the next one.

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