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Description

This image was created with the intention of adding extra configuration options to the deployment of Apache Zookeeper component on Docker. We are not associated with Apache or Zookeeper in anyway. You can find the official docker image here.

Quick reference

What is Apache Zookeeper?

Apache ZooKeeper is a software project of the Apache Software Foundation, providing an open source distributed configuration service, synchronization service, and naming registry for large distributed systems. ZooKeeper was a sub-project of Hadoop but is now a top-level project in its own right.

How to use this image

Start a single node Zookeeper server

docker run -itd --name zookeeper -p 2181:2181 -p 2888:2888 -p 3888:3888 -p 8080:8080 --restart on-failure gsiopen/zookeeper:3.6.1

Persist data

This image is runned using a non root user zookeeper who owns the /opt/zookeeper folder.

By default, zookeeper's data and datalog are stored in /opt/zookeeper/data and /opt/zookeeper/datalog. You can bind local volumes to each as follows:

docker run -itd --name zookeeper -v /path/to/store/data:/opt/zookeeper/data -v /path/to/store/datalog:/opt/zookeeper/datalog -p 2181:2181 -p 2888:2888 -p 3888:3888 -p 8080:8080 --restart on-failure gsiopen/zookeeper:3.6.1

Connect to Zookeeper from the command line client

docker exec -it zookeeper zkCli.sh

Logging

By default, ZooKeeper redirects stdout/stderr outputs to the console so you can run the next command to find logs:

docker logs zookeeper

However you can redirect logs to files in /opt/zookeeper/logs by passing the environment variable ZOO_LOG4J_PROP as follows:

docker run -itd --name zookeeper -e ZOO_LOG4J_PROP="INFO,ROLLINGFILE" -p 2181:2181 -p 2888:2888 -p 3888:3888 -p 8080:8080 --restart on-failure gsiopen/zookeeper:3.6.1

Check ZooKeeper Logging for more details.

Deploy a cluster

Environment variables below are mandatory if you want to run Zookeeper in replicated mode.

ZOO_MY_ID

The id must be unique within the ensemble and should have a value between 1 and 255.

ZOO_SERVERS

This variable allows you to specify a list of machines of the Zookeeper ensemble. Each entry has the form of server.id=<address1>:<port1>:<port2>[:role];[<client port address>:]<client port> and are separated by spaces.

Check Zookeeper Dynamic Reconfiguration for more details.

Example using docker-compose:

version: "3.7"

networks:
  private-net:
    name: private-net
    driver: bridge
    ipam:
      driver: default
      config:
        - subnet: 192.168.1.0/24

services:
  zoo-1:
    image: gsiopen/zookeeper:3.6.1
    container_name: zoo-1
    hostname: zoo-1
    environment:
      - ZOO_MY_ID=1
      - ZOO_SERVERS=server.1=0.0.0.0:2888:3888;2181 server.2=zoo-2:2888:3888;2181 server.3=zoo-3:2888:3888;2181
    restart: on-failure
    networks:
      private-net:
        ipv4_address: 192.168.1.2

  zoo-2:
    image: gsiopen/zookeeper:3.6.1
    container_name: zoo-2
    hostname: zoo-2
    environment:
      - ZOO_MY_ID=2
      - ZOO_SERVERS=server.1=zoo-1:2888:3888;2181 server.2=0.0.0.0:2888:3888;2181 server.3=zoo-3:2888:3888;2181
    restart: on-failure
    networks:
      private-net:
        ipv4_address: 192.168.1.3

  zoo-3:
    image: gsiopen/zookeeper:3.6.1
    container_name: zoo-3
    hostname: zoo-3
    environment:
      - ZOO_MY_ID=3
      - ZOO_SERVERS=server.1=zoo-1:2888:3888;2181 server.2=zoo-2:2888:3888;2181 server.3=0.0.0.0:2888:3888;2181
    restart: on-failure
    networks:
      private-net:
        ipv4_address: 192.168.1.4

Configuration

Volumes

Zookeeper uses default configuration files in the /opt/zookeeper/conf folder. You can bind an external folder with your configuration files as follows:

docker run -itd --name zookeeper -v /path/to/conf:/opt/zookeeper/conf -p 2181:2181 -p 2888:2888 -p 3888:3888 -p 8080:8080 --restart on-failure gsiopen/zookeeper:3.6.1

Environment variables

The environment configuration is controlled via the following environment variable groups or PREFIX:

CONF_ZOO: affects zoo.cfg
CONF_LOG4J: affects log4j.properties

Set environment variables with the appropriated group in the form PREFIX_PROPERTY.

Due to restriction imposed by docker and docker-compose on environment variable names the following substitution are applied to PROPERTY names:

_ => .
__ => _
___ => -

Following are some illustratory examples:

CONF_ZOO_dataLogDir=/opt/zookeeper/datalog: sets the dataLogDir property in zoo.cfg
CONF_ZOO_admin_enableServer=true: sets the admin.enableServer property in zoo.cfg

Java

Another option would be using JVMFLAGS environment variable. Many of the Zookeeper advanced configuration options can be set there using Java system properties in the form of -Dproperty=value. For example, you can use Netty instead of NIO (default option) as a server communication framework:

docker run -itd --name zookeeper -e JVMFLAGS="-Dzookeeper.serverCnxnFactory=org.apache.zookeeper.server.NettyServerCnxnFactory" -p 2181:2181 -p 2888:2888 -p 3888:3888 -p 8080:8080 --restart on-failure gsiopen/zookeeper:3.6.1

See Advanced Configuration for the full list of supported Java system properties.

Another example use case for the JVMFLAGS is setting a maximum JVM heap size of 1 GB:

docker run -itd --name zookeeper -e JVMFLAGS="-Xmx1024m" -p 2181:2181 -p 2888:2888 -p 3888:3888 -p 8080:8080 --restart on-failure gsiopen/zookeeper:3.6.1

License

View license information for the software contained in this image.

As with all Docker images, these likely also contain other software which may be under other licenses (such as Bash, etc from the base distribution, along with any direct or indirect dependencies of the primary software being contained).

As for any pre-built image usage, it is the image user's responsibility to ensure that any use of this image complies with any relevant licenses for all software contained within.