Introduction to Kafka
Official Docs
Building a Docker file
As always, we start with a dockerfile
We can build our dockerfile
cd .\messaging\kafka\
docker build . -t aimvector/kafka:2.7.0
Exploring the Kafka Install
We can then run it to explore the contents:
docker run --rm --name kafka -it aimvector/kafka:2.7.0 bash
ls -l /kafka/bin/
cat /kafka/config/server.properties
We can use the docker cp command to copy the file out of our container:
docker cp kafka:/kafka/config/server.properties ./server.properties
docker cp kafka:/kafka/config/zookeeper.properties ./zookeeper.properties
Note: We'll need the Kafka configuration to tune our server and Kafka also requires at least one Zookeeper instance in order to function. To achieve high availability, we'll run multiple kafka as well as multiple zookeeper instances in the future
Zookeeper
Let's build a Zookeeper image. The Apache folks have made it easy to start a Zookeeper instance the same way as the Kafka instance by simply running the start-zookeeper.sh script.
cd ./zookeeper
docker build . -t aimvector/zookeeper:2.7.0
cd ..
Let's create a kafka network and run 1 zookeeper instance
docker network create kafka
docker run -d `
--rm `
--name zookeeper-1 `
--net kafka `
-v ${PWD}/config/zookeeper-1/zookeeper.properties:/kafka/config/zookeeper.properties `
aimvector/zookeeper:2.7.0
docker logs zookeeper-1
Kafka - 1
docker run -d `
--rm `
--name kafka-1 `
--net kafka `
-v ${PWD}/config/kafka-1/server.properties:/kafka/config/server.properties `
aimvector/kafka:2.7.0
docker logs kafka-1
Kafka - 2
docker run -d `
--rm `
--name kafka-2 `
--net kafka `
-v ${PWD}/config/kafka-2/server.properties:/kafka/config/server.properties `
aimvector/kafka:2.7.0
Kafka - 3
docker run -d `
--rm `
--name kafka-3 `
--net kafka `
-v ${PWD}/config/kafka-3/server.properties:/kafka/config/server.properties `
aimvector/kafka:2.7.0
Topic
Let's create a Topic that allows us to store Order information.
To create a topic, Kafka and Zookeeper have scripts with the installer that allows us to do so.
Access the container:
docker exec -it zookeeper-1 bash
Create the Topic:
/kafka/bin/kafka-topics.sh \
--create \
--zookeeper zookeeper-1:2181 \
--replication-factor 1 \
--partitions 3 \
--topic Orders
Describe our Topic:
/kafka/bin/kafka-topics.sh \
--describe \
--topic Orders \
--zookeeper zookeeper-1:2181
Simple Producer & Consumer
The Kafka installation also ships with a script that allows us to produce
and consume messages to our Kafka network:
We can then run the consumer that will receive that message on that Orders topic:
docker exec -it zookeeper-1 bash
/kafka/bin/kafka-console-consumer.sh \
--bootstrap-server kafka-1:9092,kafka-2:9092,kafka-3:9092 \
--topic Orders --from-beginning
With a consumer in place, we can start producing messages
docker exec -it zookeeper-1 bash
echo "New Order: 1" | \
/kafka/bin/kafka-console-producer.sh \
--broker-list kafka-1:9092,kafka-2:9092,kafka-3:9092 \
--topic Orders > /dev/null
Once we have a message in Kafka, we can explore where it got stored in which partition:
docker exec -it kafka-1 bash
apt install -y tree
tree /tmp/kafka-logs/
ls -lh /tmp/kafka-logs/Orders-*
/tmp/kafka-logs/Orders-0:
total 4.0K
-rw-r--r-- 1 root root 10M May 4 06:54 00000000000000000000.index
-rw-r--r-- 1 root root 0 May 4 06:54 00000000000000000000.log
-rw-r--r-- 1 root root 10M May 4 06:54 00000000000000000000.timeindex
-rw-r--r-- 1 root root 8 May 4 06:54 leader-epoch-checkpoint
/tmp/kafka-logs/Orders-1:
total 4.0K
-rw-r--r-- 1 root root 10M May 4 06:54 00000000000000000000.index
-rw-r--r-- 1 root root 0 May 4 06:54 00000000000000000000.log
-rw-r--r-- 1 root root 10M May 4 06:54 00000000000000000000.timeindex
-rw-r--r-- 1 root root 8 May 4 06:54 leader-epoch-checkpoint
/tmp/kafka-logs/Orders-2:
total 8.0K
-rw-r--r-- 1 root root 10M May 4 06:54 00000000000000000000.index
-rw-r--r-- 1 root root 80 May 4 06:57 00000000000000000000.log
-rw-r--r-- 1 root root 10M May 4 06:54 00000000000000000000.timeindex
-rw-r--r-- 1 root root 8 May 4 06:54 leader-epoch-checkpoint
By seeing 0 bytes in partition 0 and 1, we know the message is sitting in partition 2 as it has 80 bytes.
We can check the message with :
cat /tmp/kafka-logs/Orders-2/*.log
Docker Compose with Kafka
So far we've taken a look at staring up Kafka and Zookeeper instances with
docker commands.
We've explored the kafka configuration and how to produce and consume messages.
Let's put it all together in a docker compose file.
With compose we'd like to be able to build our containers, pointing to a
dockerfile folder with build.context.
We'll also use volumes to mount config files.
Important note that producers and consumers are running kafka images because kafka installation comes prepacked with example consumers and producers as scripts. We override the kafka entrypoint with bash and stdin so it starts in a paused state so that we have run scripts on these instances.
Let's start with an empty docker-compose.yaml file :
version: "3.8"
services:
Zookeeper
zookeeper-1:
container_name: zookeeper-1
image: aimvector/zookeeper:2.7.0
build:
context: ./zookeeper
volumes:
- ./config/zookeeper-1/zookeeper.properties:/kafka/config/zookeeper.properties
Kafka-1 to 3
We run 3 kafka instances.
Changing the service name, container name and config mount folder:
kafka-1:
container_name: kafka-1
image: aimvector/kafka:2.7.0
build:
context: .
volumes:
- ./config/kafka-1/server.properties:/kafka/config/server.properties
- ./data/kafka-1/:/tmp/kafka-logs/
Producer
kafka-producer:
container_name: kafka-producer
image: aimvector/kafka:2.7.0
build:
context: .
working_dir: /kafka
entrypoint: /bin/bash
stdin_open: true
tty: true
Consumer
kafka-consumer:
container_name: kafka-consumer
image: aimvector/kafka:2.7.0
build:
context: .
working_dir: /kafka
entrypoint: /bin/bash
stdin_open: true
tty: true
Start the containers
cd messaging\kafka
docker compose build
docker compose up