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.
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.
Deploy a Zookeeper unit. With only one unit, the service will be running in
juju deploy apache-zookeeper zookeeper
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
juju run --service=zookeeper '/usr/lib/zookeeper/bin/zkServer.sh status'
A successful deployment will report the service mode as either
(if only one Zookeeper unit has been deployed) or
a Zookeeper quorum has been formed).
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
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')