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Replicator Tutorial on Docker

In this section, we provide a tutorial for running Replicator which replicates data from two source Kafka clusters to a destination Kafka cluster. By the end of this tutorial, you will have successfully run Replicator and replicated data for two topics from different source clusters to a destination cluster. Furthermore, you will have also set up a Kafka Connect cluster because Replicator is built on Connect.

Note

In this tutorial, Kafka and ZooKeeper are configured to store data locally in the Docker containers. For production deployments (or generally whenever you care about not losing data), you should use mounted volumes for persisting data in the event that a container stops running or is restarted. This is important when running a system like Kafka on Docker, as it relies heavily on the filesystem for storing and caching messages. For an example of how to add mounted volumes to the host machine, see the documentation on Docker external volumes.

Installing and Running Docker

For this tutorial, Docker is run using the Docker client.

To get started, you’ll need to first install Docker and get it running. The Confluent Platform Docker Images require Docker version 1.11 or greater.

Docker Client: Setting Up a Three Node Kafka Cluster

If you’re running on Windows or Mac OS X, you’ll need to use Docker Machine to start the Docker host. Docker runs natively on Linux, so the Docker host will be your local machine if you go that route. If you are running on Mac or Windows, be sure to allocate at least 4 GB of ram to the Docker Machine.

Now that you have all of the Docker dependencies installed, you can create a Docker machine and begin starting up Confluent Platform.

Note

In the following steps, each Docker container is run in detached mode and you are shown how to access to the logs for a running container. You can also run the containers in the foreground by replacing the -d flags with -it.

1. Create and configure the Docker machine.

   docker-machine create --driver virtualbox --virtualbox-memory 6000 confluent
   

   Next, configure your terminal window to attach it to your new Docker Machine:

   eval $(docker-machine env confluent)
   

2. Clone the git repository:

   git clone https://github.com/confluentinc/cp-docker-images
   cd cp-docker-images
   

3. Start the services by using the example Docker Compose file. It will start up 2 source Kafka clusters, one destination Kafka cluster and a Kafka Connect cluster. Navigate to cp-docker-images/examples/enterprise-replicator, where it is located:

   cd cp-docker-images/examples/enterprise-replicator
   

4. Start the Kafka and Kafka Connect clusters using Docker Compose create and start commands.

   docker-compose create
   

   You should see the following

   Creating enterprisereplicator_kafka-1-src-b_1
   Creating enterprisereplicator_kafka-1-src-a_1
   Creating enterprisereplicator_kafka-2-dest_1
   Creating enterprisereplicator_zookeeper-src-b_1
   Creating enterprisereplicator_zookeeper-src-a_1
   Creating enterprisereplicator_connect-host-1_1
   Creating enterprisereplicator_kafka-2-src-a_1
   Creating enterprisereplicator_kafka-2-src-b_1
   Creating enterprisereplicator_kafka-1-dest_1
   Creating enterprisereplicator_zookeeper-dest_1
   Creating enterprisereplicator_connect-host-2_1
   

   Start all the services

   docker-compose start
   

   You should see the following

   Starting kafka-1-src-b ... done
   Starting kafka-1-src-a ... done
   Starting kafka-2-dest ... done
   Starting zookeeper-src-b ... done
   Starting zookeeper-src-a ... done
   Starting connect-host-1 ... done
   Starting kafka-2-src-a ... done
   Starting kafka-2-src-b ... done
   Starting kafka-1-dest ... done
   Starting zookeeper-dest ... done
   Starting connect-host-2 ... done
   

   Before we move on, let’s make sure the services are up and running:

   docker-compose ps
   

   You should see the following:

     Name                             Command            State   Ports
   ----------------------------------------------------------------------------------
   enterprisereplicator_connect-host-1_1    /etc/confluent/docker/run   Up
   enterprisereplicator_connect-host-2_1    /etc/confluent/docker/run   Up
   enterprisereplicator_kafka-1-dest_1      /etc/confluent/docker/run   Up
   enterprisereplicator_kafka-1-src-a_1     /etc/confluent/docker/run   Up
   enterprisereplicator_kafka-1-src-b_1     /etc/confluent/docker/run   Up
   enterprisereplicator_kafka-2-dest_1      /etc/confluent/docker/run   Up
   enterprisereplicator_kafka-2-src-a_1     /etc/confluent/docker/run   Up
   enterprisereplicator_kafka-2-src-b_1     /etc/confluent/docker/run   Up
   enterprisereplicator_zookeeper-dest_1    /etc/confluent/docker/run   Up
   enterprisereplicator_zookeeper-src-a_1   /etc/confluent/docker/run   Up
   enterprisereplicator_zookeeper-src-b_1   /etc/confluent/docker/run   Up
   

   Now check the ZooKeeper logs for destination cluster to verify that ZooKeeper is healthy.

   docker-compose logs zookeeper-dest | grep -i binding
   

   You should see the following in your terminal window:

   zookeeper-dest_1   | [2016-10-20 17:31:40,784] INFO binding to port 0.0.0.0/0.0.0.0:42181 (org.apache.zookeeper.server.NIOServerCnxnFactory)
   

   Next, check the Kafka logs for the destination cluster to verify that it is healthy:

   docker-compose logs kafka-1-dest | grep -i started
   

   You should see message a message that looks like the following:

   kafka-1-dest_1     | [2016-10-20 17:31:45,364] INFO [Socket Server on Broker 1002], Started 1 acceptor threads (kafka.network.SocketServer)
   kafka-1-dest_1     | [2016-10-20 17:31:45,792] INFO [Kafka Server 1002], started (kafka.server.KafkaServer)
   ....
   

   Similarly verify that the source-a and source-b Kafka clusters are ready by running the following commands and verifying the output as described in the steps above.

   docker-compose logs zookeeper-src-a | grep -i binding
   docker-compose logs zookeeper-src-b | grep -i binding
   docker-compose logs kafka-1-src-a | grep -i started
   docker-compose logs kafka-1-src-b | grep -i started
   

   Now, you can make sure that the Connect worker is up by running the following command to search the logs:

   docker-compose logs connect-host-1 | grep started
   

   You should see the following

   connect-host-1_1   | [2016-10-20 17:31:48,942] INFO Kafka Connect started (org.apache.kafka.connect.runtime.Connect)
   connect-host-1_1   | [2016-10-20 17:31:50,403] INFO Worker started (org.apache.kafka.connect.runtime.Worker)
   connect-host-1_1   | [2016-10-20 17:31:50,988] INFO Herder started (org.apache.kafka.connect.runtime.distributed.DistributedHerder)
   

5. You will now create our first Kafka Connect Replicator connector for replicating topic “foo” from source cluster source-a.

   First, create a topic named foo.

   docker run \
     --net=host \
     --rm confluentinc/cp-kafka:5.1.4 \
     kafka-topics --create --topic foo --partitions 3 --replication-factor 2 --if-not-exists --zookeeper localhost:22181
   

   You should see the following output in your terminal window:

   Created topic "foo".
   

   Before moving on, verify that the topic was created successfully:

   docker run \
     --net=host \
     --rm confluentinc/cp-kafka:5.1.4 \
     kafka-topics --describe --topic foo --zookeeper localhost:22181
   

   You should see the following output in your terminal window:

   Topic:foo           PartitionCount:3        ReplicationFactor:2     Configs:
   Topic: foo          Partition: 0    Leader: 1002    Replicas: 1002,1001     Isr: 1002,1001
   Topic: foo          Partition: 1    Leader: 1001    Replicas: 1001,1002     Isr: 1001,1002
   Topic: foo          Partition: 2    Leader: 1002    Replicas: 1002,1001     Isr: 1002,1001
   

6. Next, we’ll try generating some data to our new topic:

   docker run \
     --net=host \
     --rm \
     confluentinc/cp-kafka:5.1.4 \
     bash -c "seq 1000 | kafka-console-producer --request-required-acks 1 --broker-list localhost:9092 --topic foo && echo 'Produced 1000 messages.'"
   

   This command will use the built-in Kafka Console Producer to produce 100 simple messages to the topic. Upon running it, you should see the following:

   Produced 1000 messages.
   

7. Now create the connector using the Kafka Connect REST API. First, let’s exec into the Connect container.

   docker-compose exec connect-host-1 bash
   

   You should see a bash prompt now. We will call this the docker exec command prompt:

   root@confluent:/#
   

   The next step is to create the Replicator connector. Run the following command on the docker exec command prompt.

   curl -X POST \
        -H "Content-Type: application/json" \
        --data '{
           "name": "replicator-src-a-foo",
           "config": {
             "connector.class":"io.confluent.connect.replicator.ReplicatorSourceConnector",
             "key.converter": "io.confluent.connect.replicator.util.ByteArrayConverter",
             "value.converter": "io.confluent.connect.replicator.util.ByteArrayConverter",
             "src.zookeeper.connect": "localhost:22181",
             "src.kafka.bootstrap.servers": "localhost:9092",
             "dest.zookeeper.connect": "localhost:42181",
             "topic.whitelist": "foo",
             "topic.rename.format": "${topic}.replica"}}'  \
        http://localhost:28082/connectors
   

   Upon running the command, you should see the following output in your docker exec command prompt:

   {"name":"replicator-src-a-foo","config":{"connector.class":"io.confluent.connect.replicator.ReplicatorSourceConnector","key.converter":"io.confluent.connect.replicator.util.ByteArrayConverter","value.converter":"io.confluent.connect.replicator.util.ByteArrayConverter","src.zookeeper.connect":"localhost:22181","src.kafka.bootstrap.servers":"localhost:9092","dest.zookeeper.connect":"localhost:42181","topic.whitelist":"foo","topic.rename.format":"${topic}.replica","name":"replicator-src-a-foo"},"tasks":[]}
   

   Before moving on, let’s check the status of the connector using curl on the docker exec command prompt.

   curl -X GET http://localhost:28082/connectors/replicator-src-a-foo/status
   

   You should see the following output including the state of the connector as RUNNING:

   {"name":"replicator-src-a-foo","connector":{"state":"RUNNING","worker_id":"localhost:38082"},"tasks":[{"state":"RUNNING","id":0,"worker_id":"localhost:28082"}]}
   

Exit the docker exec command prompt by typing exit on the prompt.

exit

1. Now that the connector is up and running, it should replicate data from foo topic on source-a cluster to foo.replica topic on the dest cluster.

   Read a sample of 1000 records from the foo.replica topic to check if the connector is replicating data to the destination Kafka cluster, as expected. Run the following command on your terminal (Make sure you have exited the docker exec command prompt):

   docker run \
     --net=host \
     --rm \
     confluentinc/cp-kafka:5.1.4 \
     kafka-console-consumer --bootstrap-server localhost:9072 --topic foo.replica --from-beginning --max-messages 1000
   

   If everything is working as expected, each of the original messages we produced should be written back out:

   1
   ....
   1000
   Processed a total of 1000 messages
   

   You will now verify that the destination topic is created with correct replication factor and partition count.

   docker run \
     --net=host \
     --rm confluentinc/cp-kafka:5.1.4 \
     kafka-topics --describe --topic foo.replica --zookeeper localhost:42181
   

   You should see that the topic foo.replica is created with 3 partitions and 2 replicas, same as the original topic foo.

   Topic:foo.replica           PartitionCount:3        ReplicationFactor:2     Configs:message.timestamp.type=CreateTime
   Topic: foo.replica          Partition: 0    Leader: 1002    Replicas: 1002,1001     Isr: 1002,1001
   Topic: foo.replica          Partition: 1    Leader: 1001    Replicas: 1001,1002     Isr: 1001,1002
   Topic: foo.replica          Partition: 2    Leader: 1002    Replicas: 1002,1001     Isr: 1002,1001
   

2. Now, we will replicate another topic from a different source cluster.

   First, create a new topic on the cluster source-b and add some data to it. Run the following commands to create and verify the topic. You should see output similar to steps 4 and 5 above:

   docker run \
     --net=host \
     --rm confluentinc/cp-kafka:5.1.4 \
     kafka-topics --create --topic bar --partitions 3 --replication-factor 2 --if-not-exists --zookeeper localhost:32181
   

   docker run \
     --net=host \
     --rm confluentinc/cp-kafka:5.1.4 \
     kafka-topics --describe --topic bar --zookeeper localhost:32181
   

   docker run \
     --net=host \
     --rm \
     confluentinc/cp-kafka:5.1.4 \
     bash -c "seq 1000 | kafka-console-producer --request-required-acks 1 --broker-list localhost:9082 --topic bar && echo 'Produced 1000 messages.'"
   

   Now exec into the Kafka Connect container and run the replicator connector. Enter the following commands on your terminal. You should see output similar to step 6 above.

   Run the following to into the container to get docker exec command prompt.

   docker-compose exec connect-host-1 bash
   

   Run the following command on the docker exec command prompt.

   curl -X POST \
        -H "Content-Type: application/json" \
        --data '{
           "name": "replicator-src-b-bar",
           "config": {
             "connector.class":"io.confluent.connect.replicator.ReplicatorSourceConnector",
             "key.converter": "io.confluent.connect.replicator.util.ByteArrayConverter",
             "value.converter": "io.confluent.connect.replicator.util.ByteArrayConverter",
             "src.zookeeper.connect": "localhost:32181",
             "src.kafka.bootstrap.servers": "localhost:9082",
             "dest.zookeeper.connect": "localhost:42181",
             "topic.whitelist": "bar",
             "topic.rename.format": "${topic}.replica"}}'  \
        http://localhost:28082/connectors
   

   curl -X GET http://localhost:28082/connectors/replicator-src-b-bar/status
   

   Exit the docker exec command prompt by typing exit on the prompt.

   exit
   

3. Now that the second replicator connector is up and running, it should replicate data from bar topic on source-b cluster to bar.replica topic on the dest cluster.

   Read data from bar.replica topic to check if the connector is replicating data properly followed by describing the topic to verify that the destination topic was created properly. You should see output similar to step 7 above. as expected.

   Run the following commands on your terminal (Make sure you have exited the docker exec command prompt):

   docker run \
     --net=host \
     --rm \
     confluentinc/cp-kafka:5.1.4 \
     kafka-console-consumer --bootstrap-server localhost:9072 --topic bar.replica --from-beginning --max-messages 1000
   

   docker run \
     --net=host \
     --rm confluentinc/cp-kafka:5.1.4 \
     kafka-topics --describe --topic bar.replica --zookeeper localhost:42181
   

4. Feel free to experiment with the replicator connector on your own now. When you are done, use the following commands to shutdown all the components.

   docker-compose stop
   

   If you want to remove all the containers, run:

   docker-compose rm