Kafka cli: Receive messages from a topic

Below statement is used to receive messages from a topic.

kafka-console-consumer --bootstrap-server {serverDetails}--topic {topicName}

Let’s see it with an example.

Step 1: Create a topic.

kafka-topics.sh --bootstrap-server localhost:9092 --topic myFirstTopic --create --partitions 3 --replication-factor 1

$kafka-topics.sh --bootstrap-server localhost:9092 --topic myFirstTopic --create --partitions 3 --replication-factor 1
$
$kafka-topics.sh --bootstrap-server localhost:9092 --list
myFirstTopic
$

Step 2: Start a consumer.

Open terminal and execute command.

kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic myFirstTopic

Step 3: Open other terminal and start sending messages to the topic.

kafka-console-producer.sh --broker-list localhost:9092 --topic myFirstTopic

Whenever you send a message to topic, you can observe that the message is received at consumer end.

At Producer End

$kafka-console-producer.sh --broker-list localhost:9092 --topic myFirstTopic
>My First Message
>My Second Message
>

At Consumer End

$kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic myFirstTopic
My First Message
My Second Message

By default, a consumer reads the messages from the time when it is created, if you want to read all the messages in the topic (Which are there before consumer creation), you need to use ‘--from-beginning’ option. I will explain about this in my next post.

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