Supported tags and respective Dockerfile links
3.4.14,3.4,latest(3.4.14/Dockerfile)3.5.4-beta,3.5(3.5.4-beta/Dockerfile)
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 Zookeeper server instance
$ docker run --name some-zookeeper --restart always -d 31z4/zookeeper
This image includes EXPOSE 2181 2888 3888 (the zookeeper client port, follower port, election port respectively), so standard container linking will make it automatically available to the linked containers. Since the Zookeeper "fails fast" it's better to always restart it.
Connect to Zookeeper from an application in another Docker container
$ docker run --name some-app --link some-zookeeper:zookeeper -d application-that-uses-zookeeper
Connect to Zookeeper from the Zookeeper command line client
$ docker run -it --rm --link some-zookeeper:zookeeper 31z4/zookeeper zkCli.sh -server zookeeper
... via docker stack deploy or docker-compose
Example stack.yml for 31z4/zookeeper:
version: '3.1'
services:
zoo1:
image: 31z4/zookeeper
restart: always
hostname: zoo1
ports:
- 2181:2181
environment:
ZOO_MY_ID: 1
ZOO_SERVERS: server.1=0.0.0.0:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
zoo2:
image: 31z4/zookeeper
restart: always
hostname: zoo2
ports:
- 2182:2181
environment:
ZOO_MY_ID: 2
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=0.0.0.0:2888:3888 server.3=zoo3:2888:3888
zoo3:
image: 31z4/zookeeper
restart: always
hostname: zoo3
ports:
- 2183:2181
environment:
ZOO_MY_ID: 3
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=0.0.0.0:2888:3888This will start Zookeeper in replicated mode. Run docker stack deploy -c stack.yml zookeeper (or docker-compose -f stack.yml up) and wait for it to initialize completely. Ports 2181-2183 will be exposed.
Please be aware that setting up multiple servers on a single machine will not create any redundancy. If something were to happen which caused the machine to die, all of the zookeeper servers would be offline. Full redundancy requires that each server have its own machine. It must be a completely separate physical server. Multiple virtual machines on the same physical host are still vulnerable to the complete failure of that host.
Consider using Docker Swarm when running Zookeeper in replicated mode.
Configuration
Zookeeper configuration is located in /conf. One way to change it is mounting your config file as a volume:
$ docker run --name some-zookeeper --restart always -d -v $(pwd)/zoo.cfg:/conf/zoo.cfg 31z4/zookeeper
Environment variables
ZooKeeper recommended defaults are used if zoo.cfg file is not provided. They can be overridden using the following environment variables.
$ docker run -e "ZOO_INIT_LIMIT=10" --name some-zookeeper --restart always -d 31z4/zookeeper
ZOO_TICK_TIME
Defaults to 2000. ZooKeeper's tickTime
The length of a single tick, which is the basic time unit used by ZooKeeper, as measured in milliseconds. It is used to regulate heartbeats, and timeouts. For example, the minimum session timeout will be two ticks
ZOO_INIT_LIMIT
Defaults to 5. ZooKeeper's initLimit
Amount of time, in ticks (see tickTime), to allow followers to connect and sync to a leader. Increased this value as needed, if the amount of data managed by ZooKeeper is large.
ZOO_SYNC_LIMIT
Defaults to 2. ZooKeeper's syncLimit
Amount of time, in ticks (see tickTime), to allow followers to sync with ZooKeeper. If followers fall too far behind a leader, they will be dropped.
ZOO_MAX_CLIENT_CNXNS
Defaults to 60. ZooKeeper's maxClientCnxns
Limits the number of concurrent connections (at the socket level) that a single client, identified by IP address, may make to a single member of the ZooKeeper ensemble.
ZOO_STANDALONE_ENABLED
Defaults to false. Zookeeper's standaloneEnabled
Prior to 3.5.0, one could run ZooKeeper in Standalone mode or in a Distributed mode. These are separate implementation stacks, and switching between them during run time is not possible. By default (for backward compatibility) standaloneEnabled is set to true. The consequence of using this default is that if started with a single server the ensemble will not be allowed to grow, and if started with more than one server it will not be allowed to shrink to contain fewer than two participants.
ZOO_AUTOPURGE_PURGEINTERVAL
Defaults to 0. Zookeeper's autoPurge.purgeInterval
New in 3.4.0: The time interval in hours for which the purge task has to be triggered. Set to a positive integer (1 and above) to enable the auto purging. Defaults to 0.
ZOO_AUTOPURGE_SNAPRETAINCOUNT
Defaults to 3. Zookeeper's autoPurge.snapRetainCount
New in 3.4.0: When enabled, ZooKeeper auto purge feature retains the autopurge.snapRetainCount most recent snapshots and the corresponding transaction logs in the dataDir and dataLogDir respectively and deletes the rest. Defaults to 3. Minimum value is 3.
Replicated mode
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. Do note that this variable will not have any effect if you start the container with a /data directory that already contains the myid file.
ZOO_SERVERS
This variable allows you to specify a list of machines of the Zookeeper ensemble. Each entry has the form of server.id=host:port:port. Entries are separated with space. Do note that this variable will not have any effect if you start the container with a /conf directory that already contains the zoo.cfg file.
In 3.5, the syntax of this has changed. Servers should be specified as such: server.id=<address1>:<port1>:<port2>[:role];[<client port address>:]<client port> Zookeeper Dynamic Reconfiguration
Where to store data
This image is configured with volumes at /data and /datalog to hold the Zookeeper in-memory database snapshots and the transaction log of updates to the database, respectively.
Be careful where you put the transaction log. A dedicated transaction log device is key to consistent good performance. Putting the log on a busy device will adversely affect performance.
How to configure logging
By default, ZooKeeper redirects stdout/stderr outputs to the console. You can redirect to a file located in /logs by passing environment variable ZOO_LOG4J_PROP as follows:
$ docker run --name some-zookeeper --restart always -e ZOO_LOG4J_PROP="INFO,ROLLINGFILE" 31z4/zookeeper
This will write logs to /logs/zookeeper.log. Check ZooKeeper Logging for more details.
This image is configured with a volume at /logs for your convenience.
License
View license information for the software contained in this image.