Overview

Apache Kafka is an open source project for a distributed publish-subscribe messaging system rethought as a distributed commit log.

Kafka stores messages in topics that are partitioned and replicated across multiple brokers in a cluster. Producers send messages to topics from which consumers read.

Created by LinkedIn and is now an Open Source project maintained by Confluent.

Kafka Use Cases

Some use cases for using Kafka:

Messaging System
Activity Tracking
Gathering metrics from many different sources
Application Logs gathering
Stream processing (with the Kafka Streams API or Spark for example)
De-coupling of system dependencies
Integration with Spark, Flink, Storm, Hadoop and many other Big Data technologies

Architecture

Source Connectors pull data from sources
Data is sent to Kafka cluster
Transformation of topic data into another topic can be done with Streams
Sink Connectors in Connect cluster pull data from Kafka
Sink Connectors push data to sinks

Kafka

Topics and Partitions

Topics: a particular stream of data

similar to a table in a database(without constraints)
you can have as many topics as you want
a topic is identified by it's name

Topics are split into partitions

each partition is ordered
each message with a partition gets an incremental id, called offset.
offsets are only relevant for a particular partition
order is guaranteed only in a partition (not across partitions)
data is assigned to a random partition unless a key is provided
you can have as many partitions per topic as you want
specifying a key, ensures that your message is written to the same partition (which ensures order).

Kafka Brokers

Consumers (still relevant? - moved to Kafka Connect?)

Data Replication

topics should have a replication factor greater than 1 (usually 2 or 3)
this ensures that if a broker goes down, another broker can serve the data
ISR - in-synch replica

Kafka Connect

Overview

Source connectors to get data from common data sources
Sink connectors to publish that data in common data sources
Make it easy for non-experienced dev to quickly get their data reliably into Kafka
Re-usable code!

Installation on Kubernetes

See https://github.com/confluentinc/cp-helm-charts

$ helm repo add confluentinc https://confluentinc.github.io/cp-helm-charts/

"confluentinc" has been added to your repositories

> helm repo update
Hang tight while we grab the latest from your chart repositories...
...Skip local chart repository
...Successfully got an update from the "confluentinc" chart repository
...Successfully got an update from the "stable" chart repository
Update Complete. ⎈ Happy Helming!⎈

$ helm install confluent-kafka confluentinc/cp-helm-charts

NAME: confluent-kafka
LAST DEPLOYED: Tue Jul 27 18:42:52 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1
NOTES:
## ------------------------------------------------------
## Zookeeper
## ------------------------------------------------------
Connection string for Confluent Kafka:
  confluent-kafka-cp-zookeeper-0.confluent-kafka-cp-zookeeper-headless:2181,confluent-kafka-cp-zookeeper-1.confluent-kafka-cp-zookeeper-headless:2181,...

To connect from a client pod:

1. Deploy a zookeeper client pod with configuration:

    apiVersion: v1
    kind: Pod
    metadata:
      name: zookeeper-client
      namespace: default
    spec:
      containers:
      - name: zookeeper-client
        image: confluentinc/cp-zookeeper:6.1.0
        command:
          - sh
          - -c
          - "exec tail -f /dev/null"

2. Log into the Pod

  kubectl exec -it zookeeper-client -- /bin/bash

3. Use zookeeper-shell to connect in the zookeeper-client Pod:

  zookeeper-shell confluent-kafka-cp-zookeeper:2181

4. Explore with zookeeper commands, for example:

  # Gives the list of active brokers
  ls /brokers/ids

  # Gives the list of topics
  ls /brokers/topics

  # Gives more detailed information of the broker id '0'
  get /brokers/ids/0## ------------------------------------------------------
## Kafka
## ------------------------------------------------------
To connect from a client pod:

1. Deploy a kafka client pod with configuration:

    apiVersion: v1
    kind: Pod
    metadata:
      name: kafka-client
      namespace: default
    spec:
      containers:
      - name: kafka-client
        image: confluentinc/cp-enterprise-kafka:6.1.0
        command:
          - sh
          - -c
          - "exec tail -f /dev/null"

2. Log into the Pod

  kubectl exec -it kafka-client -- /bin/bash

3. Explore with kafka commands:

  # Create the topic
  kafka-topics --zookeeper confluent-kafka-cp-zookeeper-headless:2181 --topic confluent-kafka-topic --create --partitions 1 --replication-factor 1 --if-not-exists

  # Create a message
  MESSAGE="`date -u`"

  # Produce a test message to the topic
  echo "$MESSAGE" | kafka-console-producer --broker-list confluent-kafka-cp-kafka-headless:9092 --topic confluent-kafka-topic

  # Consume a test message from the topic
  kafka-console-consumer --bootstrap-server confluent-kafka-cp-kafka-headless:9092 --topic confluent-kafka-topic --from-beginning --timeout-ms 2000 --max-messages 1 | grep "$MESSAGE"

$ kubectl get pods

$ kubectl get pods
NAME                                                 READY   STATUS    RESTARTS   AGE
confluent-kafka-cp-control-center-5cf9477c94-6j2tz   1/1     Running   7          49m
confluent-kafka-cp-kafka-0                           2/2     Running   0          49m
confluent-kafka-cp-kafka-1                           2/2     Running   0          38m
confluent-kafka-cp-kafka-2                           2/2     Running   0          38m
confluent-kafka-cp-kafka-connect-7646bbff9-hhdqq     2/2     Running   3          49m
confluent-kafka-cp-kafka-rest-57588d5cb5-4sfnp       2/2     Running   6          49m
confluent-kafka-cp-ksql-server-5bdd6b999c-djrj2      2/2     Running   5          49m
confluent-kafka-cp-schema-registry-8db5569b8-2qgm9   2/2     Running   6          49m
confluent-kafka-cp-zookeeper-0                       2/2     Running   0          49m
confluent-kafka-cp-zookeeper-1                       2/2     Running   0          38m
confluent-kafka-cp-zookeeper-2                       2/2     Running   0          38m

Kafka Configuration

https://docs.confluent.io/platform/current/installation/configuration/broker-configs.html#

Sample values.yaml

cp-zookeeper:
  prometheus:
    jmx:
      enabled: false
  securityContext:
    runAsUser: 1000

cp-kafka:
  nodeport:
    enabled: true
    servicePort: 19092
    firstListenerPort: 31090
  persistence:
    enabled: true
    size: 10Gi
  configurationOverrides:
    "log.retention.bytes": "7516192768"
    "delete.topic.enable": "true"
    "message.max.bytes": "1048588"
    "advertised.listeners": |-
     EXTERNAL://localhost:$((31090 + ${KAFKA_BROKER_ID}))
  prometheus:
    jmx:
      enabled: false
  securityContext:
    runAsUser: 1000

cp-schema-registry:
  prometheus:
    jmx:
      enabled: false

cp-kafka-rest:
  prometheus:
    jmx:
      enabled: false

cp-ksql-server:
  prometheus:
    jmx:
      enabled: false

cp-control-center:
  prometheus:
    jmx:
      enabled: false

Connectors

Connector	Type	URL
Azure	Kafka Sink Connector	https://www.confluent.de/hub/chaitalisagesh/kafka-connect-log-analytics
Fluent	Output Plugin for fluentbit	https://github.com/fluent/fluent-plugin-kafka
Elasticsearch	Kafka Source Connector	https://www.confluent.io/hub/dariobalinzo/kafka-connect-elasticsearch-source
Elasticsearch	Kafka Sink Connector	https://github.com/confluentinc/kafka-connect-elasticsearch
*Fluent	Output Plugin for fluentbit	https://docs.fluentbit.io/manual/pipeline/outputs/kafka

Functions

These call can all be made from the kafka-connect pod

Login to the kafka-connect pod

kubectl exec -it kafka-cp-kafka-connect-<ID> -c cp-kafka-connect-server bash

List Connectors

$ curl -s -X GET -H "Content-Type: application/json" http://kafka-cp-kafka-connect:8083/connectors

["azure-sink-connector"]

Enable a Connector

$ curl -s -X POST -H "Content-Type: application/json" --data '{"name":"azure-sink-connector","config": {"connector.cla
ss": "io.kafka.connect.log.anlaytics.sink.LogAnalyticsSinkConnector","topics" : "john-test", "key.converter": "org.apache.kafka.connect.storage.StringConverter", "value.
converter": "org.apache.kafka.connect.json.JsonConverter", "value.converter.schemas.enable": "false", "workspace.id" : "7e0d2c8e-a46c-4fd9-b274-4b07f0ba555c", "workspace
.key" : "y3n6lvRaKhDIaV6UuGn6+nuh/BoRsQI0fy9S13ZdrL/w56LUOuqrRK3ajAAnxjo8W4PAzxId0V09bJWxmtrNLA==" }}' http://kafka-cp-kafka-connect:8083/connectors


{"name":"azure-sink-connector","config":{"connector.class":"io.kafka.connect.log.anlaytics.sink.LogAnalyticsSinkConnector","topics":"john-test","key.converter":"org.apache.kafka.connect.storage.StringConverter","value.converter":"org.apache.kafka.connect.json.JsonConverter","value.converter.schemas.enable":"false","workspace.id":"7e0d2c8e-a46c-4fd9-b274-4b07f0ba555c","workspace.key":"y3n6lvRaKhDIaV6UuGn6+nuh/BoRsQI0fy9S13ZdrL/w56LUOuqrRK3ajAAnxjo8W4PAzxId0V09bJWxmtrNLA==","name":"azure-sink-connector"},"tasks":[],"type":"sink"}

Get connector details

$ curl -s -X GET -H "Content-Type: application/json" http://kafka-cp-kafka-connect:8083/connectors/azure-sink-connector

{
  "name": "azure-sink-connector",
  "config": {
    "connector.class": "io.kafka.connect.log.anlaytics.sink.LogAnalyticsSinkConnector",
    "workspace.id": "7e0d2c8e-a46c-4fd9-b274-4b07f0ba555c",
    "topics": "john-test",
    "value.converter.schemas.enable": "false",
    "name": "azure-sink-connector",
    "workspace.key": "y3n6lvRaKhDIaV6UuGn6+nuh/BoRsQI0fy9S13ZdrL/w56LUOuqrRK3ajAAnxjo8W4PAzxId0V09bJWxmtrNLA==",
    "value.converter": "org.apache.kafka.connect.json.JsonConverter",
    "key.converter": "org.apache.kafka.connect.storage.StringConverter"
  },
  "tasks": [
    {
      "connector": "azure-sink-connector",
      "task": 0
    }
  ],
  "type": "sink"
}

Delete a Connector

curl -s -X DELETE -H "Content-Type: application/json" http://kafka-cp-kafka-connect:8083/connectors/azure-sink-connector

Create a Topic

kafka-topics --zookeeper kafka-cp-zookeeper-headless:2181 --topic john-test --create --partitions 1 --replication-factor 1 --if-not-exists

Send Message to a topic

echo '{"test": 213}'| kafka-console-producer --broker-list kafka-cp-kafka-headless:9092 --topic john-test

Consume a Message from a Topic

kafka-console-consumer --bootstrap-server kafka-cp-kafka-headless:9092 --topic john-test --from-beginning --timeout-ms 2000 --max-messages 1

Debugging

Kafka Connect

Should see the following log if running:

[2021-11-16 15:24:32,204] INFO Kafka Connect started (org.apache.kafka.connect.runtime.Connect)

Kafka Broker Details (Bitnami)

Folders

Kafka Home Folder: /opt/bitnami/kafka

$ ls -l

total 48
-rw-rw-r-- 1 root root 14520 Sep 21 09:58 LICENSE
-rw-rw-r-- 1 root root   953 Sep 21 09:58 NOTICE
drwxrwxr-x 1 root root  4096 Sep 21 10:06 bin
drwxrwxr-x 1 root root  4096 Oct  5 03:34 config
drwxrwxr-x 1 root root  4096 Sep 21 10:06 libs
drwxrwxr-x 1 root root  4096 Sep 21 10:06 licenses
drwxrwxr-x 1 root root  4096 Oct  6 17:14 logs
drwxrwxr-x 1 root root  4096 Sep 21 10:06 site-docs

Commands

## Creating new Topics

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --create \
            --topic kafka.learning.tweets \
            --partitions 1 \
            --replication-factor 1

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --create \
            --topic kafka.learning.alerts \
            --partitions 1 \
            --replication-factor 1

## Listing Topics

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --list

## Getting details about a Topic

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --describe


## Publishing Messages to Topics

        ./kafka-console-producer.sh \
            --bootstrap-server localhost:29092 \
            --topic kafka.learning.tweets

## Consuming Messages from Topics

        ./kafka-console-consumer.sh \
            --bootstrap-server localhost:29092 \
            --topic kafka.learning.tweets \
            --from-beginning

## Deleting Topics

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --delete \
            --topic kafka.learning.alerts

#Create a Topic with multiple partitions

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --create \
            --topic kafka.learning.orders \
            --partitions 3 \
            --replication-factor 1


#Check topic partitioning

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --topic kafka.learning.orders \
            --describe

## Publishing Messages to Topics with keys

        ./kafka-console-producer.sh \
            --bootstrap-server localhost:29092 \
            --property "parse.key=true" \
            --property "key.separator=:" \
            --topic kafka.learning.orders

## Consume messages using a consumer group

        ./kafka-console-consumer.sh \
            --bootstrap-server localhost:29092 \
            --topic kafka.learning.orders \
            --group test-consumer-group \
            --property print.key=true \
            --property key.separator=" = " \
            --from-beginning

## Check current status of offsets

        ./kafka-consumer-groups.sh \
            --bootstrap-server localhost:29092 \
            --describe \
            --all-groups

## Creating the Topic

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --create \
            --topic kafka.usecase.students \
            --partitions 2 \
            --replication-factor 1

## Describe the Topic

        ./kafka-topics.sh \
            --zookeeper zookeeper:2181 \
            --topic kafka.usecase.students \
            --describe

## Publish to the Topic

        ./kafka-console-producer.sh \
            --bootstrap-server localhost:29092 \
            --property "parse.key=true" \
            --property "key.separator=:" \
            --topic kafka.usecase.students

## Consume Message from the Topic

        ./kafka-console-consumer.sh \
            --bootstrap-server localhost:29092 \
            --topic kafka.usecase.students \
            --group usecase-consumer-group \
            --property print.key=true \
            --property key.separator=" = " \
            --from-beginning

REST Api

Pushing Message to Topic

Publish a Message

curl -X POST -H "Content-Type: application/vnd.kafka.json.v2+json" \
      --data ' { "records": [ { "value": {"log":"value"} }]}' \ 
      "http://localhost:8082/topics/ncyd_test_in"

{"offsets":[{"partition":0,"offset":0,"error_code":null,"error":null}],"key_schema_id":null,"value_schema_id":null}%

Consuming Messages from a Topic

Create a Consumer

curl -X POST -H "Content-Type: application/vnd.kafka.v2+json" \
      --data '{"name": "test_consumer", "format": "json", "auto.offset.reset": "earliest"}' \
      http://localhost:8082/consumers/test_consumer

{"instance_id":"test_consumer","base_uri":"http://ckaf-rest-0.ckaf-rest-headless.default.svc.cluster.local:8082/consumers/test_consumer/instances/test_consumer"}%

Subscribe to a Topic

curl -X POST -H "Content-Type: application/vnd.kafka.v2+json" \
     --data '{"topics":["ncyd_test_in"]}' \
     http://localhost:8082/consumers/test_consumer/instances/test_consumer/subscription

Consume the Messages

curl -X GET -H "Accept: application/vnd.kafka.json.v2+json" \
http://localhost:8082/consumers/test_consumer/instances/test_consumer/records

[{"topic":"ncyd_test_in","key":null,"value":{"log":"value"},"partition":0,"offset":0}]%

References

Reference	URL
Apache Kafka in 5 minutes	https://www.youtube.com/watch?v=PzPXRmVHMxI
Nokia Learning - Kafka	https://nokialearn.csod.com/ui/lms-learning-details/app/course/dc425d19-5642-535f-916c-211768f90a00
Kafka Topics, Partitions and Offsets Explained	https://www.youtube.com/watch?v=_q1IjK5jjyU
Kafka Helm Charts	https://github.com/confluentinc/cp-helm-charts
Confluent for Kubernetes	https://docs.confluent.io/operator/current/overview.html#operator-about-intro

Space shortcuts

Page tree

Overview

Kafka Use Cases

Architecture

Kafka

Topics and Partitions

Kafka Brokers

Consumers (still relevant? - moved to Kafka Connect?)

Data Replication

Kafka Connect

Overview

Installation on Kubernetes

Kafka Configuration

Connectors

Functions

Login to the kafka-connect pod

List Connectors

Enable a Connector

Get connector details

Delete a Connector

Create a Topic

Send Message to a topic

Consume a Message from a Topic

Kafka Broker Details (Bitnami)

Folders

Commands

REST Api

Pushing Message to Topic

Consuming Messages from a Topic

References