Juju is an Open Source Charmed Operator Framework. It helps you move from configuration management to application management and has two main components:
Charmed Operator Lifecycle Manager (OLM) - a hybrid-cloud application management and orchestration system that helps you from Day 0 to Day 2. Deploy, configure, scale, integrate, maintain and manage Kubernetes native, container-native and VM-native applications – and the relations between them.
- Charmed Operators, packaged as “Charms”, are software that encapsulate a single application and all the code and know-how it takes to operate it on Kubernetes or machines.
Charmed Operator SDK - a guide to help you build Charmed Operators for use with the Charmed OLM.
This guide introduces you to Juju and charmed operators deployment on a local Ubuntu machine. If you are using MS Windows or macOS you can still follow this tutorial by installing Multipass. By the end of this guide you will have a running web application backed by a database.
Alternatively, if you would like to start with Juju on Kubernetes, please follow the Getting Started on Kubernetes guide.
The following sections provide a basic overview of using Juju, from installation to deploying and relating charmed operator.
Create the test environment
MS Windows and macOS users. Optional step for Ubuntu users.
- Install Juju CLI
- Create a local cloud
- Bootstrap the Juju OLM controller
- Deploy a charmed operator
- Relate charmed operators
1. Creating the test environment
The instructions in this tutorial are based on an Ubuntu system. This section details how to quickly create a test environment on MS Windows and macOS using a virtual machine deployed by Multipass.
This section is also useful for those that are already running Ubuntu, but would like to create an isolated test environment that could be easily removed.
Info: Multipass is a tool for quickly running virtual machines from any host operating system. This will allow you to create a fully-isolated test environment that won’t impact your host system.
You can find system specific information on how to install Multipass at multipass.run.
It only takes a few minutes!
Create a virtual machine
To start a virtual machine
microcloud that has 8 GB RAM allocated to it, execute:
multipass launch -n microcloud -m 8g -c 2 -d 20G
Multipass will confirm the creation:
multipass has downloaded the latest Long Term Support version of the Ubuntu operating system, you will be able to enter a command-line with the
multipass shell microcloud
This gives you access to the shell (you may see a different prompt, depending on the version installed):
You are now ready to follow the rest of this guide in our newly created Ubuntu machine. All commands should be typed in this shell. Once you are done, you can run ‘$ multipass destroy microcloud’ and uninstall Multipass to remove any trace of this guide.
2. Install Juju CLI
We will install Juju CLI via a snap package: this is the easiest and fastest way to get started with Juju. We also provide installation instruction on several other systems.
Other installation methods
You can find a comprehensive list of all the ways you have to install Juju at https://juju.is/docs/installing.
The following command will install Juju CLI:
sudo snap install juju --classic
If the installation was successful, you will see the following message:
juju 2.8.10 from Canonical✓ installed
3. Create a local cloud
We will use LXD for creating a cloud on the localhost. LXD should be already installed in your Ubuntu system.
LXD is a system container and virtual machine manager. Juju uses it to instantiate the containers need for the app.
Need to install LXD? Visit the LXD docs for installation instructions.
Juju speaks directly to the local LXD daemon, which also requires lxd group membership.
newgrp lxd sudo adduser $USER lxd
LXD then needs to be configured for its environment:
lxd init --auto
Verify that the localhost cloud is available
localhost cloud is now established. We can verify that by running
Juju should have detected the presence of LXD and has added it as the
[...] localhost 1 localhost lxd LXD Container Hypervisor
4. Bootstrap the Juju controller
Juju uses an active software agent, called the controller, to manage applications. The controller is installed on a machine through the bootstrap process:
juju bootstrap localhost overlord
During the bootstrap process, Juju connects with the cloud, then provision a machine to install the controller on, then install it.
Creating Juju controller "overlord" on localhost/localhost Looking for packaged Juju agent version 2.6.8 for amd64 [...]
5. Deploying a charmed operator: Hello Juju!
The first workload that you’ll deploy is a simple web application. You’ll deploy an application that uses the Flask microframework to send “Hello Juju!” via HTTP.
juju deploy hello-juju
The charmed operator name
hello-juju is resolved into an actual charmed operator version by contacting the charmhub.io. This charmed operator is then downloaded by the controller and used as the source of the application that was created with the same name:
Located charm "cs:hello-juju-4". Deploying charm "cs:hello-juju-4".
The next step is to use
juju expose to configure the necessary security groups and firewall rules and make the
hello-world application publicly available over the network:
juju expose hello-juju
Checking the deployment
Now that a workload is in place, use
juju status to inspect what is happening. It can take a few minutes for the application to start up, but once it’s ready, the output will show that the status of the
hello-juju app is active:
Model Controller Cloud/Region Version SLA Timestamp default overlord localhost/localhost 2.8.10 unsupported 16:24:04+12:00 App Version Status Scale Charm Store Rev OS Notes hello-juju active 1 hello-juju jujucharms 4 ubuntu Unit Workload Agent Machine Public address Ports Message hello-juju/0* active idle 0 10.47.112.215 80/tcp Machine State DNS Inst id Series AZ Message 0 started 10.47.112.215 juju-646ac9-0 bionic Running
Connecting to the application
juju status output above provided the “Public address” of the
hello-juju/0 unit as
10.47.112.215 and its Ports column as
80/tcp. Let’s connect!
If the connection was successful, you will see:
6. Relating another application: adding PostgreSQL to the deployment
Relations are Juju’s defining concept and its main point of difference with other systems in its class. They enable the simplicity, security and stability offered by the whole project.
hello-juju web server maintains a count for each greeting that it has sent out via the
By default, this state is maintained within a SQLite database that is set up by the
hello-juju charmed operator itself. In this section, we will deploy a PostgreSQL database and relate it to our hello-juju charmed operator.
To deploy the PostgreSQL database, we will use the same
juju deploy postgresql
Located charm "cs:postgresql-199". Deploying charm "cs:postgresql-199".
The PostgreSQL charm may take a few moments to be deployed. You can check the status of the deployment by running:
When ready, the field
status will ready
active. You should wait for the charm deployment to finish before following the next steps.
To relate the two charmed operators, all we need to do is run:
juju relate postgresql:db hello-juju
The applications will auto-configure themselves. You now have a web application and a database deployed and ready to use without having to deal with application specific configuration!
Find more information about relations and how they work.
Re-checking the deployment status
Now that the new application and a relation are in place, the
juju status output has expanded.
juju status --relations
--relations option include relations information:
Model Controller Cloud/Region Version SLA Timestamp default overlord localhost/localhost 2.8.10 unsupported 16:24:04+12:00 App Version Status Scale Charm Store Rev OS Notes hello-juju active 1 hello-juju jujucharms 3 ubuntu postgresql 10.10 active 1 postgresql jujucharms 199 ubuntu Unit Workload Agent Machine Public address Ports Message hello-juju/0* active idle 0 10.47.112.215 80/tcp postgresql/0* active idle 0 10.47.112.216 5432/tcp Live master (10.10) Machine State DNS Inst id Series AZ Message 0 started 10.47.112.215 juju-646ac9-0 bionic Running 1 started 10.47.112.216 juju-646ac9-1 bionic Running Relation provider Requirer Interface Type Message postgresql:coordinator postgresql:coordinator coordinator peer postgresql:db hello-juju:db pgsql regular postgresql:replication postgresql:replication pgpeer peer