Zookeeper

juju deploy zookeeper

16.04 LTS

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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. Use it off-the-shelf to implement consensus, group management, leader election, and presence protocols. Learn more at zookeeper.apache.org.

This charm provides version 3.4.6 of the Zookeeper component from Apache Bigtop.

Deploying

This charm requires Juju 2.0 or greater. If Juju is not yet set up, please follow the getting-started instructions prior to deploying this charm.

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

juju deploy zookeeper

Network-Restricted Environments

Charms can be deployed in environments with limited network access. To deploy in this environment, configure a Juju model with appropriate proxy and/or mirror options. See Configuring Models for more information.

Configuring Network Interfaces

In some network environments, zookeeper may need to be restricted to listen for incoming connections on a specific network interface (e.g.: for security reasons). To do so, configure zookeeper with either a network interface name or a CIDR range specifying a subnet. For example:

juju config zookeeper network_interface=eth0
juju config zookeeper network_interface=10.0.2.0/24

Each zookeeper unit in the cluster will lookup the IP address of that network interface, or find the first network interface with an IP address in the specified subnet, and bind Zookeeper to that address.

If a mistake is made and an invalid name for the network interface is configured, recover by re-configuring with the correct name and then run "juju resolved" on any failed units:

juju config zookeeper network_interface=eth0
juju resolved zookeeper/0

To go back to listening on all interfaces, configure zookeeper with network_interface=0.0.0.0:

juju config zookeeper network_interface=0.0.0.0

Verifying

Status

Apache Bigtop charms provide extended status reporting to indicate when they are ready:

juju status

This is particularly useful when combined with watch to track the on-going progress of the deployment:

watch -n 2 juju status

The message column will provide information about a given unit's state. This charm is ready for use once the status message indicates that it is ready.

Smoke Test

This charm provides a smoke-test action that can be used to verify the application is functioning as expected. Run the action as follows:

juju run-action zookeeper/0 smoke-test

Watch the progress of the smoke test actions with:

watch -n 2 juju show-action-status

Eventually, the action should settle to status: completed. If it reports status: failed, the application is not working as expected. Get more information about a specific smoke test with:

juju show-action-output <action-id>

Utilities

This charm includes Zookeeper command line utilities that can also be used to verify that the application is running as expected. Check the status of the Zookeeper daemon with zkServer.sh:

juju run --application=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).

Scaling

Running ZooKeeper in standalone mode is convenient for evaluation, some development, and testing. In production, however, ZooKeeper should be run 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.

In order to add new Zookeeper servers to the quorum, simply add more units. For example, add two more zookeeper units with:

juju add-unit -n 2 zookeeper

The Zookeeper nodes will automatically perform a rolling restart to update the Zookeeper quorum without losing any jobs in progress. Once the rolling restart has completed, all of the Zookeeper nodes should report the following status:

ready (n units)

(Where 'n' is the total number of Zookeeper units in the quorum.)

Integrating

To integrate Zookeeper into solutions with other charms, update the charms that require Zookeeper as follows:

1) Add following lines to metadata.yaml:

requires:
  zookeeper:
     interface: zookeeper

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

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

Issues

Apache Bigtop tracks issues using JIRA (Apache account required). File an issue for this charm at:

https://issues.apache.org/jira/secure/CreateIssue!default.jspa

Ensure Bigtop is selected as the project. Typically, charm issues are filed in the deployment component with the latest stable release selected as the affected version. Any uncertain fields may be left blank.

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