5.0 KiB
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/
cat /kafka/config/server.properties
ls -l /kafka/bin
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/zookeeper.properties
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 .\messaging\kafka\zookeeper
docker build . -t aimvector/zookeeper:2.7.0
Let's create a kafka network and run 1 zookeeper instance
docker network create kafka
docker run -d --rm --name zookeeper --net kafka zookeeper
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
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 bash
Create the Topic:
/kafka/bin/kafka-topics.sh \
--create \
--zookeeper zookeeper:2181 \
--replication-factor 1 \
--partitions 3 \
--topic Orders
Describe our Topic:
/kafka/bin/kafka-topics.sh \
--describe \
--topic Orders \
--zookeeper zookeeper:2181
We can take a look at how Kafka stores data
apt install -y tree
tree /tmp/kafka-logs/
Simple Producer & Consumer
The Kafka installation also ships with a script that allows us to produce and consume messages to our Kafka network:
echo "New Order: 1" | \
/kafka/bin/kafka-console-producer.sh \
--broker-list kafka-1:9092 \
--topic Orders > /dev/null
We can then run the consumer that will receive that message on that Orders topic:
/kafka/bin/kafka-console-consumer.sh \
--bootstrap-server kafka-1:9092 \
--topic Orders --from-beginning
Once we have a message in Kafka, we can explore where it got stored in which partition:
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
Building a Producer: Go
docker run -it `
--net kafka `
-e KAFKA_PEERS="kafka-1:9092,kafka-2:9092,kafka-3:9092" `
-e KAFKA_TOPIC="Orders" `
-e KAFKA_PARTITION=1 `
-p 80:80 `
kafka-producer
Building a Consumer: Go
cd messaging\kafka\applications\consumer
docker build . -t kafka-consumer
docker run -it `
--net kafka `
-e KAFKA_PEERS="kafka-1:9092,kafka-2:9092,kafka-3:9092" `
-e KAFKA_TOPIC="Orders" `
kafka-consumer
High Availability + Replication
Next up, we'll take a look at achieving high availability using replication techniques and taking advantage of Kafka's distributed architecture.