With Juju 2.0 around the corner we’d like to dedicate this month’s tips section to Leadership. In the Juju context when we say Leadership we mean the Leader election concept as defined for distributed computing. Leadership election provides you (as a charm author) with a means of querying the various nodes of your service for leadership status, setting status, and ensuring that all your units are in a consistent state with regard to an authoritative source for charm configuration settings.
We’ve had documentation for how to use leadership in your charm for a while now, however with the advent of the new layer based approach for charms, we felt now would be a good time to show you the leadership layer. Like all layers, it removes the need to manually write your own hooks.
This layer will initialize charms.reactive states, allowing you to write handlers that will be activated by these states. It allows you to completely avoid writing leader-elected and leader-settings-changed hooks. As a simple example, these two handlers are all that is required to make the leader unit generate a password if it is not already set,
and have the shared password stored in a file on all units:
python import charms.leadership from charmhelpers.core.host import pwgen @when('leadership.is_leader') @when_not('leadership.set.admin_password') def generate_secret(): charms.leadership.leader_set(admin_password=pwgen()) @when('leadership.changed.admin_password') def store_secret(): write_file('/etc/foopass', leader_get('admin_password'))
You can find the rest of the tutorial in the layer README file, which includes instructions on how to get started and advanced usage.
You can find this layer, along with dozens of other reusable layers on interfaces.juju.solutions. If you’re interested in contributing layers, or reusing layers to make your charms simpler and easier to maintain, let us know.
Spicule offer application modelling and deployment service. Spicule can help migrate existing applications on or off premise, provide training to your system administrators or manage the systems themselves. Spicule also offers development services for companies who use or are considering using the Juju platform and require software not currently available in the charm store to be made available to their platform.
WANdisco will be charming their Fusion Platform, which delivers core functionality supporting continuous availability and performance. Fusion guarantees data consistency across Hadoop clusters deployed on any combination of distributions, Hadoop compatible storage systems or cloud environments any distance apart.
The Canonical team will be travelling to Austin, for the OpenStack Summit – a four day conference for developers, users and administrators of OpenStack software.
If you are planning to attend the OpenStack Summit, join us to discuss your cloud strategy and learn about our solutions:
Juju Office Hours is a freeflow meeting where we discuss what’s happening in and around the ecosystem, what hot new changes are landing in charms and Juju itself, and our favorite part, you can join in and ask the team questions about anything Juju related.
Date: Friday, 25 March 2016
Time: 2100 (9pm) UTC, 1600 (4pm) EST, 1300 (1pm) PST
Where: http://ubuntuonair.com for the stream
Participate: #juju on freenode
We will cover as many topics as we can in an hour, and take questions
from the crowd. If you want to participate in the hangout itself ping
me ahead of time and we’d love to have you onboard.
Over 100 Juju enthusiasts gathered this week for our second Juju Charmer Summit in beautiful Gent, Belgium as part of the Config Management Camp. Check out our summary of the event and don’t forget to watch our video sessions online.
Contact us! For more information on the Charm Partner Programme, please visit http://partners.ubuntu.com/programmes/charm
Ubuntu offers all the training, software infrastructure, tools, services and support you need for your public and private clouds.
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