kafka-docker

Dockerfile for Apache Kafka

The image is available directly from Docker Hub

Pre-Requisites

• install docker-compose https://docs.docker.com/compose/install/
• set an environment variable DOCKER_HOST_IP to match your docker host IP (Note: Do not use localhost or 127.0.0.1 as the host ip if you want to run multiple brokers.)
• if you want to customize any Kafka parameters, simply add them as environment variables in docker-compose.yml, e.g. in order to increase the message.max.bytes parameter set the environment to KAFKA_MESSAGE_MAX_BYTES: 2000000. To turn off automatic topic creation set KAFKA_AUTO_CREATE_TOPICS_ENABLE: 'false'
• Kafka's log4j usage can be customized by adding environment variables prefixed with LOG4J_. These will be mapped to log4j.properties. For example: LOG4J_LOGGER_KAFKA_AUTHORIZER_LOGGER=DEBUG, authorizerAppender

Usage

Start a cluster:

• docker-compose up -d

Add more brokers:

• docker-compose scale kafka=3

Destroy a cluster:

• docker-compose stop

Note

The default docker-compose.yml should be seen as a starting point. By default each broker will get a new port number and broker id on restart. Depending on your use case this might not be desirable. If you need to use specific ports and broker ids, modify the docker-compose configuration accordingly, e.g. docker-compose-single-broker.yml:

• docker-compose -f docker-compose-single-broker.yml up

Broker IDs

You can configure the broker id in different ways

1. explicitly, using KAFKA_BROKER_ID
2. via a command, using BROKER_ID_COMMAND, e.g. BROKER_ID_COMMAND: "hostname | awk -F'-' '{print $2}'"

If you don't specify a broker id in your docker-compose file, it will automatically be generated (see https://issues.apache.org/jira/browse/KAFKA-1070. This allows scaling up and down. In this case it is recommended to use the --no-recreate option of docker-compose to ensure that containers are not re-created and thus keep their names and ids.

Automatically create topics

If you want to have kafka-docker automatically create topics in Kafka during creation, a KAFKA_CREATE_TOPICS environment variable can be added in docker-compose.yml.

Here is an example snippet from docker-compose.yml:

    environment:
      KAFKA_CREATE_TOPICS: "Topic1:1:3,Topic2:1:1:compact"

Topic 1 will have 1 partition and 3 replicas, Topic 2 will have 1 partition, 1 replica and a cleanup.policy set to compact.

Advertised hostname

You can configure the advertised hostname in different ways

1. explicitly, using KAFKA_ADVERTISED_HOST_NAME
2. via a command, using HOSTNAME_COMMAND, e.g. HOSTNAME_COMMAND: "route -n | awk '/UG[ \t]/{print $$2}'"

When using commands, make sure you review the "Variable Substitution" section in https://docs.docker.com/compose/compose-file/

If KAFKA_ADVERTISED_HOST_NAME is specified, it takes precedence over HOSTNAME_COMMAND

For AWS deployment, you can use the Metadata service to get the container host's IP:

HOSTNAME_COMMAND=wget -t3 -T2 -qO-  http://169.254.169.254/latest/meta-data/local-ipv4

Reference: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html

Broker Rack

You can configure the broker rack affinity in different ways

1. explicitly, using KAFKA_BROKER_RACK
2. via a command, using RACK_COMMAND, e.g. RACK_COMMAND: "curl http://169.254.169.254/latest/meta-data/placement/availability-zone"

In the above example the AWS metadata service is used to put the instance's availability zone in the broker.rack property.

JMX

For monitoring purposes you may wish to configure JMX. Additional to the standard JMX parameters, problems could arise from the underlying RMI protocol used to connect

• java.rmi.server.hostname - interface to bind listening port
• com.sun.management.jmxremote.rmi.port - The port to service RMI requests

For example, to connect to a kafka running locally (assumes exposing port 1099)

  KAFKA_JMX_OPTS: "-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Djava.rmi.server.hostname=127.0.0.1 -Dcom.sun.management.jmxremote.rmi.port=1099"
  JMX_PORT: 1099

Jconsole can now connect at jconsole 192.168.99.100:1099

Listener Configuration

Newer versions of Kafka have deprecated advertised.host.name and advertised.port in favor of a more flexible listener configuration that supports multiple listeners using the same or different protocols. This image supports up to three listeners to be configured automatically as shown below.

Note: if the below listener configuration is not used, legacy conventions for "advertised.host.name" and "advertised.port" still operate without change.

1. Use KAFKA_LISTENER_SECURITY_PROTOCOL_MAP to configure an INSIDE, OUTSIDE, and optionally a BROKER protocol. These names are arbitrary but used for consistency and clarity.
   • KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: INSIDE:PLAINTEXT,OUTSIDE:SSL,BROKER:PLAINTEXT configures three listener names, but only the listener named OUTSIDE uses SSL. Note this example does not concern extra steps in configuring SSL on a broker.
2. Use KAFKA_ADVERTISED_PROTOCOL_NAME to set the name from the protocol map to be used for the "advertised.listeners" property. This is "OUTSIDE" in this example.
3. Use KAFKA_PROTOCOL_NAME to set the name from the protocol map to be used for the "listeners" property. This is "INSIDE" in this example.
4. Use KAFKA_INTER_BROKER_LISTENER_NAME to set the name from the protocol map to be used for the "inter.broker.listener.name". This defaults to KAFKA_PROTOCOL_NAME if not supplied. This is "BROKER" in the example.
5. Use KAFKA_ADVERTISED_PORT and KAFKA_ADVERTISED_HOST_NAME (or the HOSTNAME_COMMAND option) to set the name and port to be used in the advertised.listeners list.
6. Use KAFKA_PORT and KAFKA_HOST_NAME (optional) to set the name (optional) and port to be used in the listeners list. If KAFKA_HOST_NAME is not defined, Kafka's reasonable default behavior will be used and is sufficient. Note that KAFKA_PORT defaults to "9092" if not defined.
7. Use KAFKA_INTER_BROKER_LISTENER_PORT to set the port number to be used in both advertised.listeners and listeners for the Inter-broker listener. The host name for this listener is not configurable. Kafka's reasonable default behavior is used.

Example

Given the environment seen here, the following configuration will be written to the Kafka broker properties.

HOSTNAME_COMMAND: curl http://169.254.169.254/latest/meta-data/public-hostname
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: INSIDE:PLAINTEXT,OUTSIDE:PLAINTEXT
KAFKA_ADVERTISED_PROTOCOL_NAME: OUTSIDE
KAFKA_PROTOCOL_NAME: INSIDE
KAFKA_ADVERTISED_PORT: 9094

The resulting configuration:

advertised.listeners = OUTSIDE://ec2-xx-xx-xxx-xx.us-west-2.compute.amazonaws.com:9094,INSIDE://:9092
listeners = OUTSIDE://:9094,INSIDE://:9092
inter.broker.listener.name = INSIDE

Rules

• No listeners may share a port number.
• An advertised.listener must be present by name and port number in the list of listeners.
• You must not set "security.inter.broker.protocol" at the same time as using this multiple-listener mechanism.

Best Practices

• Reserve port 9092 for INSIDE listeners.
• Reserve port 9093 for BROKER listeners.
• Reserve port 9094 for OUTSIDE listeners.

Docker Swarm Mode

The listener configuration above is necessary when deploying Kafka in a Docker Swarm using an overlay network. By separating OUTSIDE and INSIDE listeners, a host can communicate with clients outside the overlay network while still benefiting from it from within the swarm.

In addition to the multiple-listener configuration, additional best practices for operating Kafka in a Docker Swarm include:

• Use "deploy: global" in a compose file to launch one and only one Kafka broker per swarm node.
• Use compose file version '3.2' (minimum Docker version 16.04) and the "long" port definition with the port in "host" mode instead of the default "ingress" load-balanced port binding. This ensures that outside requests are always routed to the correct broker. For example:

ports:
   - target: 9094
     published: 9094
     protocol: tcp
     mode: host

Older compose files using the short-version of port mapping may encounter Kafka client issues if their connection to individual brokers cannot be guaranteed.

See the included sample compose file docker-compose-swarm.yml

Tutorial

http://wurstmeister.github.io/kafka-docker/