Overview
Duration: 3:00
Before you get started!
Welcome to the world of operators! In this series of tutorials, we will walk you through all the necessary steps to explore and learn operators through some basic examples. Starting with just your laptop, you will learn how to use operators for sophisticated application management at scale, across multiple Kubernetes clusters, cloud virtual machines, and ultimately bare metal.
This tutorial assumes you have successfully completed the previous tutorial - “6. Updates”.
What are operators?
Operators are pieces of software designed to drive other software. They encapsulate the operational code of applications, shifting the burden of lifecycle management from configuration files and manual steps to an operator instance. Operators are a form of automation that is gaining popularity in the Kubernetes domain where traditional configuration management does not work. However, operators work with traditional virtual and bare metal machines as well.
What is Juju OLM?
Juju is a universal Operator Lifecycle Manager (OLM) which provides services to operators. It provides resources for operators, deploys them, manages their lifecycle, delivers configuration updates, etc. Juju OLM is universal, meaning that it supports container substrates like Kubernetes as well as traditional machine substrates like bare metal, VMware, OpenStack, or public cloud instances.
In this tutorial, you will learn how to:
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Remove an application unit with an operator
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Remove an application with all its units and relations
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Remove all deployed applications with their units and relations
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Remove Juju controller that was previously bootstrapped
You will only need:
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A machine with 8 GB of RAM
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Microk8s and Juju installed
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Juju controller bootstrapped on MicroK8s
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The Prometheus and Grafana operators deployed to Microk8s
Remove an application unit
Duration: 5:00
Operators and Juju OLM provide lifecycle management capabilities so that applications can be torn down in a fully automated way.
In the following steps, we will remove one of the deployed application units, the application itself, and finally, the entire Juju model. We will also outline how to remove the Juju controller.
First, let’s see what the current status of the model is:
$ juju status
Model Controller Cloud/Region Version SLA Timestamp
monitoring mk8s microk8s/localhost 2.9.9 unsupported 14:13:42+01:00
App Version Status Scale Charm Store Channel Rev OS Address Message
grafana-k8s grafana/grafana@7f26ece active 1 grafana-k8s local 0 kubernetes 10.152.183.126
prometheus-k8s prom/prometheus:latest active 2 prometheus-k8s charmhub stable 1 kubernetes 10.152.183.7
Unit Workload Agent Address Ports Message
grafana-k8s/0* active idle 10.1.98.62 3000/TCP
prometheus-k8s/0* active idle 10.1.98.51 9090/TCP
prometheus-k8s/1 active idle 10.1.98.5 9090/TCP
As we can see, there are two units of the Prometheus application. We can remove one of the units by executing the following command:
$ juju remove-unit prometheus-k8s --num-units=1
scaling down to 1 units
and watch the changes by running the juju status command in the “watch” loop:
$ watch --color 'juju status --color'
Model Controller Cloud/Region Version SLA Timestamp
monitoring mk8s microk8s/localhost 2.9.9 unsupported 14:30:03+01:00
App Version Status Scale Charm Store Channel Rev OS Address Message
grafana-k8s grafana/grafana@7f26ece active 1 grafana-k8s local 0 kubernetes 10.152.183.126
prometheus-k8s prom/prometheus:latest waiting 1 prometheus-k8s charmhub stable 1 kubernetes 10.152.183.7
Unit Workload Agent Address Ports Message
grafana-k8s/0* active executing 10.1.98.17 3000/TCP
prometheus-k8s/0* active idle 10.1.98.51 9090/TCP
prometheus-k8s/1 terminated executing 10.1.98.4 9090/TCP unit stopped by the cloud
Relation provider Requirer Interface Type Message
grafana-k8s:grafana grafana-k8s:grafana grafana-peers peer
grafana-k8s:grafana-source prometheus-k8s:grafana-source grafana-datasource regular
After a while the “prometheus/1” unit should be removed, resulting in the following output:
$ juju status
Model Controller Cloud/Region Version SLA Timestamp
monitoring mk8s microk8s/localhost 2.9.9 unsupported 14:30:35+01:00
App Version Status Scale Charm Store Channel Rev OS Address Message
grafana-k8s grafana/grafana@7f26ece active 1 grafana-k8s local 0 kubernetes 10.152.183.126
prometheus-k8s prom/prometheus:latest active 1 prometheus-k8s charmhub stable 1 kubernetes 10.152.183.7
Unit Workload Agent Address Ports Message
grafana-k8s/0* active idle 10.1.98.17 3000/TCP
prometheus-k8s/0* active idle 10.1.98.51 9090/TCP
Relation provider Requirer Interface Type Message
grafana-k8s:grafana grafana-k8s:grafana grafana-peers peer
grafana-k8s:grafana-source prometheus-k8s:grafana-source grafana-datasource regular
Remove an application
Duration: 5:00
In a similar way, we can remove the entire Prometheus application. When removing an application, Juju will clean up all relations setup by that application and remove all units containing that application.
In order to completely remove Prometheus, execute the following command:
$ juju remove-application prometheus-k8s
removing application prometheus-k8s
- will detach storage database/0
Again, we can watch the changes by running the “watch” loop with the juju status command:
$ watch --color 'juju status --color'
After a period of time, Prometheus is fully removed from our deployment:
$ juju status
Model Controller Cloud/Region Version SLA Timestamp
monitoring mk8s microk8s/localhost 2.9.9 unsupported 14:32:05+01:00
App Version Status Scale Charm Store Channel Rev OS Address Message
grafana-k8s grafana/grafana@7f26ece active 1 grafana-k8s local 0 kubernetes 10.152.183.126
Unit Workload Agent Address Ports Message
grafana-k8s/0* active idle 10.1.98.56 3000/TCP
Relation provider Requirer Interface Type Message
grafana-k8s:grafana grafana-k8s:grafana grafana-peers peer
Remove the model
Duration: 5:00
In order to remove all deployed applications with their units and relations, we can use juju destroy-model command. We will cover Juju models in detail in the next tutorial, but as of now, simply execute the following command, which is an interactive prompt, so enter y to continue as there is no way to recover after this has been done:
$ juju destroy-model monitoring --release-storage
WARNING! This command will destroy the "monitoring" model.
This includes all containers, applications, data and other resources.
Continue [y/N]? y
Destroying model
Waiting for model to be removed, 1 application(s), 5 volume(s), 5 filesystems(s)...
Waiting for model to be removed, 1 application(s), 1 volume(s), 1 filesystems(s)....
Waiting for model to be removed, 1 application(s)......
Waiting for model to be removed...
Model destroyed.
The “monitoring” is the name of the current model that we created in previous tutorials. We can see that all deployed applications with their units and relations are being removed. Finally, the model itself is removed too:
$ juju models
Controller: mk8s
Model Cloud/Region Type Status Access Last connection
controller microk8s/localhost kubernetes available admin just now
We can also verify that all containers have been cleaned up by running the “kubectl: command:
$ microk8s.kubectl get pods -n monitoring
No resources found in monitoring namespace.
Remove the controller
Duration: 3:00
In some situations, you may want to remove the entire Juju controller. That will result in removing all models created under this controller, all applications, applications units, and their relations.
NOTE: The following instructions are provided for informational purposes only. The next tutorials assume you have Juju controller bootstrapped. In case you accidentally remove it, refer to the following tutorial - 1. Ready! Steady! Go! - for exact instructions on how to bootstrap a Juju controller.
In order to remove Juju controller, execute the following command:
$ juju destroy-controller --destroy-all-models --release-storage mk8s
WARNING! This command will destroy the "mk8s" controller.
This includes all machines, applications, data and other resources.
Continue? (y/N):y
Destroying controller
Waiting for hosted model resources to be reclaimed
All hosted models reclaimed, cleaning up controller machines
The “mk8s” is the name of the controller that we bootstrapped in previous tutorials. Once the command stops executing, the controller is removed:
$ juju controllers
Next steps
Duration: 2:00
Congratulations! You have reached the end of this tutorial.
You can now move to the next tutorial - “8. Models”
In this tutorial you have learnt how to:
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Remove an application unit with an operator
-
Remove an application with all its units and relations
-
Remove all deployed applications with their units and relations
-
Remove Juju controller that was previously bootstrapped