AMQ Streams with Kafka Connect

In the previous article in this series, we discussed the basics of Red Hat AMQ Streams on Red Hat OpenShift. Here are a few key points to keep in mind before we proceed:

  • AMQ Streams is based on Apache Kafka.
  • AMQ Streams for the OpenShift Container Platform is based on the Strimzi project.
  • AMQ Streams on containers has multiple components, such as the Cluster Operator, Entity Operator, Mirror Maker, Kafka connect, and Kafka Bridge.

Now, let's continue on to setting up Kafka Connect, the Kafka Bridge, and Mirror Maker.

Kafka Connect

Kafka Connect is mainly used to stream data in and out of Kafka clusters; for instance, getting a Twitter feed and then pushing it to the cluster. We need to understand Kafka Connect's concepts before continuing:

  • Connectors define where the data should be copied to or from.
  • Tasks are the actors that actually copy the data.
  • Workers are used to schedule units of work for connectors and tasks.
  • Converters are used by task units to change data format.
  • Transforms are used by connector units to do simple data adjustments, routing, and chain transformations.

Note: For more details on the basic concepts, I recommend reading Kafka Connect Concepts.

Creating a simple Kafka Connect instance

A Kafka Connect instance in OpenShift can be created using two different Kube objects: KafkaConnect and KafkaConnectS2I. By default, Kafka Connect includes two built-in connectors: FileStreamSourceConnector and FileStreamSinkConnector. However, before you build a new connector, first check the catalog of existing connectors.

Let us set up a simple Kafka Connect instance and then perform the source and sink operations. Then, we can add a default producer sample app and a consumer sample app. This process will show multiple publishers and multiple consumers, as shown in Figure 1:

The structure for our example.
Figure 1: The overall structure for this example.

Begin by creating the Kafka Connect config amq-kafka-connect.yml. The example file present in examples/kafka-connect/kafka-connect.yml was used as a reference for this config file:

kind: KafkaConnect
  name: simple-connect-cluster
  version: 2.3.0
  replicas: 1
  bootstrapServers: simple-cluster-kafka-bootstrap:9093
      - secretName: simple-cluster-cluster-ca-cert
        certificate: ca.crt

Next, execute the YAML:

$ oc create -f amq-kafka-connect.yml

You can see the result in Figure 2:

Kafka Connect is is deployed.
Figure 2: The new deployment is in place.

Preparing to test your new Kafka Connect instance

Let us set up to test the new instance by doing the following:

  1. Create a new config, which will sink from the redhat-demo-topics topic content to the file amq-demo-sink.txt:
$ oc rsh simple-cluster-kafka-0
sh-4.2$ curl -X POST -H "Content-Type: application/json" --data '{"name": "redhat-file-sink-demo", "config": {"connector.class":"FileStreamSinkConnector", "tasks.max":"1", "file":"/tmp/amq-demo-sink.txt", "topic":"redhat-demo-topics", "value.converter.schemas.enable" : "false", "value.converter" : "", "value.converter.schemas.enable" : "false", "key.converter" : "", "key.converter.schemas.enable" : "false"}}' http://simple-connect-cluster-connect-api.amq-streams.svc:8083/connectors

Here is the output:

  1. Create a new config that will source into the redhat-demo-topics topic content from the file amq-demo-source.txt:
$ oc rsh simple-cluster-kafka-0
sh-4.2$ curl -X POST -H "Content-Type: application/json" --data '{"name": "redhat-file-source-demo", "config": {"connector.class":"FileStreamSourceConnector", "tasks.max":"1", "file":"/tmp/amq-demo-source.txt", "topic":"redhat-demo-topics", "value.converter.schemas.enable" : "false", "value.converter" : "", "value.converter.schemas.enable" : "false", "key.converter" : "", "key.converter.schemas.enable" : "false"}}' http://simple-connect-cluster-connect-api.amq-streams.svc:8083/connectors

Here is the output:

  1. In a new terminal start the producer sample app:
$ oc run kafka-producer -ti --rm=true --restart=Never -- bin/ --broker-list simple-cluster-kafka-bootstrap:9092 --topic redhat-demo-topics
  1. In a new terminal start the consumer sample app:
$ oc run kafka-consumer -ti --rm=true --restart=Never -- bin/ --bootstrap-server simple-cluster-kafka-bootstrap:9092 --topic redhat-demo-topics --from-beginning

Testing your new Kafka Connect instance

To test your instance, do the following:

  1. Log into the Kafka Connect pod and watch the /tmp/amq-demo-sink.txt file:
$ oc get po | grep connect
simple-connect-cluster-connect-7479b86c7-tmdbp 1/1 Running 0 3h
$ oc rsh simple-connect-cluster-connect-7479b86c7-tmdbp
sh-4.2$ tail -100f /tmp/amq-demo-sink.txt

hello world
from pramod

Here, you can see that the connector has already sunk two messages into the file.

  1.  Log into the Kafka Connect pod in a different terminal, then add content into /tmp/amq-demo-source.txt:
$ oc rsh simple-connect-cluster-connect-7479b86c7-tmdbp
sh-4.2$ echo redhat-is-my-world > /tmp/amq-demo-source.txt

This set of commands writes a message in /tmp/amq-demo-sink.txt, and also to the consumer sample app. Figure 3 shows the connector source push and sink output:

The connector's push and sink output.
Figure 3: The connector source pushing the message redhat-is-my-world in the second terminal.

Figure 4 shows the sample app consuming the message:

The sample app consuming the message.
Figure 4: The results on the consuming side.
  1. Now, send a message from the producer sample app. Figure 5 shows how this message flows through the system in three parts. From top to bottom, these are the connector sink, the consumer sample app, and then the producer sample app pushing the message kafka connect sample app:
The message flowing through each step.
Figure 5: The message kafka connect sample app passing through each stage.

Kafka Bridge

The Bridge component helps us connect to the Kafka Cluster using the HTTP or AMQP protocol. In this article, we demo the HTTP usage as shown in Figure 6:

Our structure including the Kafka Bridge.
Figure 6: How the Kafka Bridge fits in through the HTTP protocol.

Kafka Bridge produces a REST API for the HTTP protocol, through which it provides multiple operations, such as:

  • Sending messages.
  • Subscribing to topics.
  • Receiving messages.
  • Committing offsets.
  • Seeking specific positions.

Creating your Kafka Bridge

  1. Create the kafka-bridge config file amq-kafka-bridge.yml. The example file present in examples/kafka-bridge/kafka-bridge.yaml was used as a reference for the following config:
kind: KafkaBridge
  name: simple-bridge
  replicas: 1
  bootstrapServers: simple-cluster-kafka-bootstrap:9092
    port: 8080
  1. Create the bridge in OCP:
$ oc create -f amq-kafka-bridge.yml

You can see the results in Figure 7:

The Kafka Bridge is deployed.
Figure 7: Your new Kafka Bridge.
  1. Create a route so that we can access the bridge from outside the cluster:
$ oc expose svc simple-bridge-bridge-service --name=simple-bridge-route

Testing your HTTP protocol-based Kafka Bridge

  1. Create the Kafka topic config amq-kafka-topic.yml and apply it to the cluster:
kind: KafkaTopic
  name: simple-topic
  labels: simple-cluster
  partitions: 5
  replicas: 1
  config: 7200000
    segment.bytes: 1073741824
oc create -f amq-kafka-topic.yml
  1. Get the route URL for the bridge endpoints:
#get the route to do the curl command

oc get route

simple-bridge-route simple-bridge-bridge-service rest-api None
  1. Publish a message on simple-topic:
curl -X POST \ \
-H 'content-type: application/vnd.kafka.json.v2+json' \
-d '{
"records": [
"value": "all hail the shadowman"

Here is the output:

  1. Create the consumer group simple-rh-bridge-consumer-group and the instance simple-rh-bridge-consumer. For this task, we set the message format to JSON:
curl -X POST \ \
-H 'content-type: application/vnd.kafka.v2+json' \
-d '{
"name": "simple-rh-bridge-consumer",
"auto.offset.reset": "earliest",
"format": "json",
"": false,
"fetch.min.bytes": 512,
"": 30000
  1. Create a subscriber for the simple-topic created in step one:
curl -X POST \
-H 'content-type: application/vnd.kafka.v2+json' \
-d '{
"topics": [
  1. Consume the messages (note that the first request will register and the subsequent calls will provide the array of messages):
curl -X GET \
-H 'accept: application/vnd.kafka.json.v2+json'

Here is the output:

curl -X GET \
-H 'accept: application/vnd.kafka.json.v2+json'

And the additional output:

[{"topic":"simple-topic","key":null,"value":"all hail the shadowman","partition":0,"offset":0}]

Mirror Maker

Kafka Mirror Maker replicates data from one Kafka cluster to another. The usual use case is across different data centers.

For the purpose of this demo, we use two different namespaces and projects, namely amq-streams and amq-streams-dc2. Doing so is the same as having multiple data centers with the same names. This setup is shown in Figure 8:

Our structure for replicating multiple data centers.
Figure 8: Replicating multiple data centers with Kafka Mirror Maker.

Kafka Mirror maker consumes from the active Kafka cluster and produces to the mirror (backup) Kafka cluster.

Setting up for the example

To demo the Kafka Mirror Maker, we need to create another namespace and Kafka cluster. First, create the new namespace amq-streams-dc2:

$ oc new-project amq-streams-dc2

Next, create a new Kafka cluster:

$ sed -i 's/namespace: .*/namespace: amq-streams-dc2/' install/cluster-operator/*RoleBinding*.yaml

On macOS, use the following instead:

$ sed -i '' 's/namespace: .*/namespace: amq-streams-dc2/' install/cluster-operator/*RoleBinding*.yaml
$ oc apply -f install/cluster-operator -n amq-streams-dc2
$ oc apply -f amq-kafka-cluster.yml -n amq-streams-dc2

You can see the result in Figure 9:

All of the components installed so far.
Figure 9: All of the pieces are in place so far.

Creating a mirror with Kafka Mirror Maker

Create a kafka-mirror-maker config amq-kafka-mirror-maker.yml. In this file, we increase the consumer stream to two for faster response and use the group ID simple-source-group-id for the consumer. Additionally, we whitelist all of the topics using wildcards. This example file present in examples/kafka-mirror-maker/kafka-mirror-maker.yaml was used as a reference for the config:

kind: KafkaMirrorMaker
  name: simple-mirror-maker
  version: 2.3.0
  replicas: 1
    bootstrapServers: simple-cluster-kafka-bootstrap:9092
    groupId: simple-source-group-id
    numStreams: 2
    bootstrapServers: simple-cluster-kafka-bootstrap.amq-streams-dc2.svc:9092
  whitelist: ".*"
Create the Mirror Maker in the amq-streams namespace:
$ oc create -f amq-kafka-mirror-maker.yml -n amq-streams

You can see the result in Figure 10:

Mirror Maker is deployed.
Figure 10: Your new Mirror Maker instance.

Testing Kafka Mirror Maker

To test the Mirror Maker, create the following two namespaces: amq-streams and amq-streams-dc2. The amq-streams namespace will contain the producer sample app to produce new messages, and the consumer sample app to consume new messages. The amq-streams-dc2 namespace will contain the consumer sample app so it can consume new messages, so it can show that the messages are getting pushed to the DC2 cluster.

  1. Create a producer sample app and consumer sample app in the amq-streams namespace:
$ oc project amq-streams
$ oc run kafka-producer -ti --rm=true --restart=Never -- bin/ --broker-list simple-cluster-kafka-bootstrap:9092 --topic redhat-demo-topics
$ oc run kafka-consumer -ti --rm=true --restart=Never -- bin/ --bootstrap-server simple-cluster-kafka-bootstrap:9092 --topic redhat-demo-topics
  1. Create a Consumer sample app in the amq-streams-dc2 namespace
$ oc project amq-streams-dc2
$ oc run kafka-consumer -ti --rm=true --restart=Never -- bin/ --bootstrap-server simple-cluster-kafka-bootstrap:9092 --topic redhat-demo-topics
  1. Send a message from the producer sample app.

Is Mirror Maker working? You should see the message in the consumer app in both the namespaces, as shown in Figure 11:

The message flowing through the components.
Figure 11: Your message flowing from the producer to both the consumer and the backup consumer.


In this article, we explored Red Hat AMQ Streams components like Kafka Connect, Kafka Bridge, and Mirror Maker. In the third and final part of the series, we will cover monitoring and administration.


Last updated: March 29, 2023