apache zookeeper #0

Supports: xenial trusty

Description

Apache ZooKeeper is a centralized, reliable, service for maintaining configuration information, naming, providing distributed synchronization, and group services. All of these kinds of services are used in some form or another by distributed applications. In order to install and configure Apache HBase and other Hadoop ecosystem components, you must start the ZooKeeper service.


Overview

Apache ZooKeeper is a high-performance coordination service for distributed applications. It exposes common services such as naming, configuration management, synchronization, and group services in a simple interface so you don't have to write them from scratch. You can use it off-the-shelf to implement consensus, group management, leader election, and presence protocols.

Usage

Deploy a Zookeeper unit. With only one unit, the service will be running in standalone mode:

juju deploy apache-zookeeper zookeeper

Scaling

Running ZooKeeper in standalone mode is convenient for evaluation, some development, and testing. But in production, you should run ZooKeeper in replicated mode. A replicated group of servers in the same application is called a quorum, and in replicated mode, all servers in the quorum have copies of the same configuration file.

Scaling Zookeeper to create a quorum is trivial. The following will add two additional Zookeeper units and will automatically configure them with knowledge of the other quorum members based on their peer relation to one another:

juju add-unit -n 2 zookeeper

Test the deployment

Test if the Zookeeper service is running by using the zkServer.sh script:

juju run --service=zookeeper '/usr/lib/zookeeper/bin/zkServer.sh status'

A successful deployment will report the service mode as either standalone (if only one Zookeeper unit has been deployed) or leader / follower (if a Zookeeper quorum has been formed).

REST API

Zookeeper REST Api can be enabled/disabled either through an action or via a config variable:

juju action do zookeeper/0 start-rest
juju action do zookeeper/0 stop-rest

or

juju set zookeeper rest=true

Integrate Zookeeper into another charm

1) Add following lines to your charm's metadata.yaml:

requires:
  zookeeper:
     interface: zookeeper

2) Add a zookeeper-relation-changed hook to your charm. Example contents:

from charmhelpers.core.hookenv import relation_get
ZK_hostname = relation_get('private-address')
ZK_port = relation_get('port')

Contact Information

bigdata@lists.ubuntu.com

Help


Configuration

network_interface
(string) A string containing the name of a network interface, or a CIDR range. For split network environments, or for other secure environments, you may wish to bind to a specific network interface. You may either name the interface here, or specify a CIDR range that contains the IP of the network interface. The charm will translate that into a specific IP address to bind to, and drop that into the Zookeeper config. To reset the bindings, pass in 0.0.0.0.
resources_mirror
(string) URL from which to fetch resources (e.g., Hadoop binaries) instead of Launchpad.
rest
(boolean) Set to true/false to enable/disable the REST Api server.