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).
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')
Deploying in Network-Restricted Environments
This charm can be deployed in environments with limited network access. To
deploy in this environment, you will need a local mirror to serve the packages
and resources required by this charm.
Mirroring Packages
You can setup a local mirror for apt packages using squid-deb-proxy.
For instructions on configuring juju to use this, see the
Juju Proxy Documentation.
Mirroring Resources
In addition to apt packages, this charm requires a few binary resources
which are normally hosted on Launchpad. If access to Launchpad is not
available, the jujuresources library makes it easy to create a mirror
of these resources:
sudo pip install jujuresources
juju resources fetch --all apache-zookeeper/resources.yaml -d /tmp/resources
juju resources serve -d /tmp/resources
This will fetch all of the resources needed by this charm and serve them via a
simple HTTP server. You can then set the resources_mirror config option to
have the charm use this server for retrieving resources.
Contact Information
Help
Configuration
- resources_mirror
- (string) URL from which to fetch resources (e.g., Hadoop binaries) instead of Launchpad.
