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https://github.com/ches/docker-kafka

Apache Kafka on Docker
https://github.com/ches/docker-kafka

apache-kafka docker docker-image kafka

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Apache Kafka on Docker

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Apache Kafka on Docker

======================



This repository holds a build definition and supporting files for building a

[Docker] image to run [Kafka] in containers. It is published as an Automated

Build [on Docker Hub], as `ches/kafka`.



This build intends to provide an operator-friendly Kafka deployment suitable for

usage in a production Docker environment:



  - It runs one service, no bundled ZooKeeper (for more convenient development,

    use [Docker Compose]!).

  - Configuration is parameterized, enabling a Kafka cluster to be run from

    multiple container instances.

  - Kafka data and logs can be handled outside the container(s) using volumes.

  - JMX is exposed, for Kafka and JVM metrics visibility.



If you find any shortcomings with the build regarding operability, pull requests

or feedback via GitHub issues are welcomed.



[Docker Compose]: https://docs.docker.com/compose/



Usage Quick Start

-----------------



Here is a minimal-configuration example running the Kafka broker service, then

using the container as a client to run the basic producer and consumer example

from [the Kafka Quick Start]:



```

# A non-default bridge network enables convenient name-to-hostname discovery

$ docker network create kafka-net



$ docker run -d --name zookeeper --network kafka-net zookeeper:3.4

$ docker run -d --name kafka --network kafka-net --env ZOOKEEPER_IP=zookeeper ches/kafka



$ docker run --rm --network kafka-net ches/kafka \

>   kafka-topics.sh --create --topic test --replication-factor 1 --partitions 1 --zookeeper zookeeper:2181

Created topic "test".



# In separate terminals:

$ docker run --rm --interactive --network kafka-net ches/kafka \

>   kafka-console-producer.sh --topic test --broker-list kafka:9092



$ docker run --rm --network kafka-net ches/kafka \

>   kafka-console-consumer.sh --topic test --from-beginning --bootstrap-server kafka:9092

```



### Volumes



The container exposes two volumes that you may wish to bind-mount, or process

elsewhere with `--volumes-from`:



- `/data`: Path where Kafka's data is stored (`log.dirs` in Kafka configuration)

- `/logs`: Path where Kafka's logs (`INFO` level) will be written, via log4j



### Ports and Linking



The container publishes two ports:



- `9092`: Kafka's standard broker communication

- `7203`: JMX publishing, for e.g. jconsole or VisualVM connection



Kafka requires Apache ZooKeeper. You can satisfy the dependency by simply

linking another container that exposes ZooKeeper on its standard port of 2181,

as shown in the above example, **ensuring** that you link using an alias of

`zookeeper`.



Alternatively, you may configure a specific address for Kafka to find ZK. See

the Configuration section below.



### A more complex local development setup



This example shows more configuration options and assumes that you wish to run a

development environment with Kafka ports mapped directly to localhost, for

instance if you're writing a producer or consumer and want to avoid rebuilding a

container for it to run in as you iterate. This requires that localhost is your

Docker host, i.e. your workstation runs Linux. If you're using something like

boot2docker, substitute the value of `boot2docker ip` below.



```bash

$ mkdir -p kafka-ex/{data,logs} && cd kafka-ex

$ docker run -d --name zookeeper --publish 2181:2181 zookeeper:3.4

$ docker run -d \

    --hostname localhost \

    --name kafka \

    --volume ./data:/data --volume ./logs:/logs \

    --publish 9092:9092 --publish 7203:7203 \

    --env KAFKA_ADVERTISED_HOST_NAME=127.0.0.1 --env ZOOKEEPER_IP=127.0.0.1 \

    ches/kafka

```



Configuration

-------------



Some parameters of Kafka configuration can be set through environment variables

when running the container (`docker run -e VAR=value`). These are shown here

with their default values, if any:



- `KAFKA_BROKER_ID=0`



  Maps to Kafka's `broker.id` setting. Must be a unique integer for each broker

  in a cluster.

- `KAFKA_PORT=9092`



  Maps to Kafka's `port` setting. The port that the broker service listens on.

  You will need to explicitly publish a new port from container instances if you

  change this.

- `KAFKA_ADVERTISED_HOST_NAME=`



  Maps to Kafka's `advertised.host.name` setting. Kafka brokers gossip the list

  of brokers in the cluster to relieve producers from depending on a ZooKeeper

  library. This setting should reflect the address at which producers can reach

  the broker on the network, i.e. if you build a cluster consisting of multiple

  physical Docker hosts, you will need to set this to the hostname of the Docker

  *host's* interface where you forward the container `KAFKA_PORT`.

- `KAFKA_ADVERTISED_PORT=9092`



  As above, for the port part of the advertised address. Maps to Kafka's

  `advertised.port` setting. If you run multiple broker containers on a single

  Docker host and need them to be accessible externally, this should be set to

  the port that you forward to on the Docker host.

- `KAFKA_DEFAULT_REPLICATION_FACTOR=1`



  Maps to Kafka's `default.replication.factor` setting. The default replication

  factor for automatically created topics.

- `KAFKA_NUM_PARTITIONS=1`



  Maps to Kafka's `num.partitions` setting. The default number of log partitions

  per topic.

- `KAFKA_AUTO_CREATE_TOPICS_ENABLE=true`



  Maps to Kafka's `auto.create.topics.enable`.

- `KAFKA_INTER_BROKER_PROTOCOL_VERSION`



  Maps to Kafka's `inter.broker.protocol.version`. If you have a cluster that

  runs brokers with different Kafka versions make sure they communicate with

  the same protocol version.

- `KAFKA_LOG_MESSAGE_FORMAT_VERSION`



  Maps to Kafka's `log.message.format.version`. Specifies the protocol version

  with which your cluster communicates with its consumers.

- `KAFKA_LOG_RETENTION_HOURS=168`



  Maps to Kafka's `log.retention.hours`. The number of hours to keep a log file

  before deleting it.



- `KAFKA_MESSAGE_MAX_BYTES`



  Maps to Kafka's `message.max.bytes`. The maximum size of message that the

  server can receive. Default: 1000012



- `KAFKA_REPLICA_FETCH_MAX_BYTES`



  Maps to Kafka's `replica.fetch.max.bytes`. The number of bytes of messages to 

  attempt to fetch for each partition. This is not an absolute maximum, if 

  the first message in the first non-empty partition of the fetch is larger 

  than this value, the message will still be returned to ensure that progress 

  can be made. The maximum message size accepted by the broker is defined via 

  message.max.bytes (broker config) or max.message.bytes (topic config). 

  Default: 1048576



- `JAVA_RMI_SERVER_HOSTNAME=$KAFKA_ADVERTISED_HOST_NAME`



  Maps to the `java.rmi.server.hostname` JVM property, which is used to bind the

  interface that will accept remote JMX connections. Like

  `KAFKA_ADVERTISED_HOST_NAME`, it may be necessary to set this to a reachable

  address of *the Docker host* if you wish to connect a JMX client from outside

  of Docker.

- `ZOOKEEPER_IP=`



  **Required** if no container is linked with the alias "zookeeper" and

  publishing port 2181, or not using `ZOOKEEPER_CONNECTION_STRING` instead. Used

  in constructing Kafka's `zookeeper.connect` setting.

- `ZOOKEEPER_PORT=2181`



  Used in constructing Kafka's `zookeeper.connect` setting.

- `ZOOKEEPER_CONNECTION_STRING=`



  Set a string with host:port pairs for connecting to a ZooKeeper Cluster. This

  setting overrides `ZOOKEEPER_IP` and `ZOOKEEPER_PORT`.

- `ZOOKEEPER_CHROOT`, ex: `/v0_8_1`



  ZooKeeper root path used in constructing Kafka's `zookeeper.connect` setting.

  This is blank by default, which means Kafka will use the ZK `/`. You should

  set this if the ZK instance/cluster is shared by other services, or to

  accommodate Kafka upgrades that change schema. Starting in Kafka 0.8.2, it

  will create the path in ZK automatically; with earlier versions, you must

  ensure it is created before starting brokers.



JMX

---



Remote JMX access can be a bit of a pain to set up. The start script for this

container tries to make it as painless as possible, but it's important to

understand that if you want to connect a client like VisualVM from outside other

Docker containers (e.g. directly from your host OS in development), then you'll

need to configure RMI to be addressed *as the Docker host IP or hostname*. If

you have set `KAFKA_ADVERTISED_HOST_NAME`, that value will be used and is

probably what you want. If not (you're only using other containers to talk to

Kafka brokers) or you need to override it for some reason, then you can instead

set `JAVA_RMI_SERVER_HOSTNAME`.



For example in practice, if your Docker host is VirtualBox run by Docker

Machine, a `run` command like this should allow you to connect VisualVM from

your host OS to `$(docker-machine ip docker-vm):7203`:



    $ docker run -d --name kafka -p 7203:7203 \

        --link zookeeper:zookeeper \

        --env JAVA_RMI_SERVER_HOSTNAME=$(docker-machine ip docker-vm) \

        ches/kafka



Note that it is fussy about port as well—it may not work if the same port

number is not used within the container and on the host (any advice for

workarounds is welcome).



Finally, please note that by default remote JMX has authentication and SSL

turned off (these settings are taken from Kafka's own default start scripts). If

you expose the JMX hostname/port from the Docker host in a production

environment, you should make make certain that access is locked down

appropriately with firewall rules or similar. A more advisable setup in a Docker

setting would be to run a metrics collector in another container, and link it to

the Kafka container(s).



If you need finer-grained configuration, you can totally control the relevant

Java system properties by setting `KAFKA_JMX_OPTS` yourself—see `start.sh`.



Fork Legacy

-----------



This image/repo was originally forked from [relateiq/kafka]. My original

motivations for forking were:



- Change the Kafka binary source to an official Apache artifact. RelateIQ's was

  on a private S3 bucket, and this opaqueness is not suitable for a

  publicly-shared image for reasons of trust.

- Changes described in [this pull request](https://github.com/relateiq/docker-kafka/pull/4).



After a period of unresponsiveness from upstream on pull requests and my repo

tallying far more downloads on Docker Hub, I have made further updates and

changes with the expectation of maintaining independently from here on. This

project's changelog file describes these in detail.



[Docker]: http://www.docker.io

[Kafka]: http://kafka.apache.org

[on Docker Hub]: https://hub.docker.com/r/ches/kafka/

[relateiq/kafka]: https://github.com/relateiq/docker-kafka

[the Kafka Quick Start]: http://kafka.apache.org/documentation.html#quickstart