AHMED ZBYR

AHMED ZBYR

Biker, EV Enthusiast

Apache Kafka is publish-subscribe messaging rethought as a distributed commit log. Kafka is a distributed, partitioned, replicated commit log service. It provides the functionality of a messaging system, but with a unique design. What does all that mean?

First let’s review some basic messaging terminology:

  • Kafka maintains feeds of messages in categories called topics.
  • We’ll call processes that publish messages to a Kafka topic producers.
  • We’ll call processes that subscribe to topics and process the feed of published messages consumers..
  • Kafka is run as a cluster comprised of one or more servers each of which is called a broker.

http://kafka.apache.org/documentation.html

Download and Extract

Download the tgz file and extract.

[kafka-admin@kafka Downloads]$ ls
jdk-7u75-linux-x64.rpm  kafka_2.9.2-0.8.2.0.tgz
[kafka-admin@kafka Downloads]$ sudo rpm -ivh jdk-7u75-linux-x64.rpm
...
[kafka-admin@kafka Downloads]$ sudo tar -xzf kafka_kafka_2.9.2-0.8.2.0.tgz -C /opt
[kafka-admin@kafka Downloads]$ cd /opt
[kafka-admin@kafka opt]$ sudo ln -s kafka_2.9.2-0.8.2.0 kafka
[kafka-admin@kafka opt]$ ls
kafka  kafka_2.9.2-0.8.2.0
[kafka-admin@kafka opt]$ sudo chmod kafka-admin:kafka-admin -R kafka

Now we are ready to start all the services required.

[kafka-admin@kafka opt]$ cd kafka
[kafka-admin@kafka kafka]$ ls
bin  config  libs  LICENSE  logs  NOTICE
[kafka-admin@kafka kafka]$ bin/zookeeper-server-start.sh config/zookeeper.properties

This will start us a zookeeper in localhost on port 2181. This configuration can be changed in the config/zookeeper.properties file. NOTE : If you want to run the zookeeper on a separate machine make sure the change in the config/server.properties so that the kafka server points to the correct zookeeper. By default it points to localhost:2181.

Next we start server.

[kafka-admin@kafka kafka]$ bin/kafka-server-start.sh config/server.properties

NOTE : If you want to start multiple make sure you make multiple copies of the server.properties file and change the below information.

  1. broker.id is the unique identifier for the service.
  2. port where this server is going to listen on.

  3. log.dir where to right the log.

    config/server-1.properties: broker.id=1 port=9093 log.dir=/tmp/kafka-logs-1

    config/server-2.properties: broker.id=2 port=9094 log.dir=/tmp/kafka-logs-2

Now our server has started, lets assume we start only one server.

Creating Topics

To create a topic just execute below command, this will create a single partition.

[kafka-admin@kafka kafka]$ bin/kafka-topics.sh --create --zookeeper localhost:2181 \
                                        --replication-factor 1 --partitions 1 --topic test

To check topics currently running. Execute below command.

[kafka-admin@kafka kafka]$ bin/kafka-topics.sh --list --zookeeper localhost:2181
test
[kafka-admin@kafka kafka]$

We see currently we have only one topic. Now we are all set to send and recv messages.

Send some message

Open up a new terminal and fire up the Kafka producer script as below. And start typing some message \n or cr will be end of each message

[kafka-admin@kafka kafka]$ bin/kafka-console-producer.sh --broker-list localhost:9092 \
                                                                                    --topic test
                                                                                    
This is a message
This is a message2

Start a Consumer

Open a new terminal and start the consumer.

Option --from-beginning will give all the messages from the beginning. You will see 2 messages as we typed above This is a message and This is a message2.

[kafka-admin@kafka kafka]$ bin/kafka-console-consumer.sh --zookeeper localhost:2181 \
                                                                --topic test --from-beginning
This is a message
This is a message2

Our single node Kafka cluster is Ready.

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