(from-zero-to-hero-write-your-first-kubernetes-charm)=
# From zero to hero: Write your first Kubernetes charm

This tutorial will introduce you to the official way to write a Kubernetes charm --- that is, how to equip an application with all the operational logic that it needs so that you can manage it on any Kubernetes cloud with just a few commands, using Juju. 

```{important}

**Did you know?** Writing a charm is also known as 'charming'!

```

<!--
We will charm a simple web application  based on the Python FastAPI framework.

The web application uses the PostgreSQL database and has a Prometheus metrics scrape target. As such, we will also integrate it with -->

<!--You will go through the process of *charming a web application.  
What does *charming* and *Charmed Operator* mean? *Charmed Operator* means all of the domain knowledge and expertise about an application distilled in clean and maintainable Python code.  

The  application that we will charm in this tutorial is based on the Python FastAPI framework, uses the PostgreSQL database, and has a Prometheus metrics scrape target. Once it is *charmed*, we will integrate our charm with the existing PostgreSQL charm and the Canonical Observability Stack (COS) bundle, for monitoring purposes.
-->

**What you'll need:** 

- A working station, e.g., a laptop with amd64 architecture. 
- Familiarity with Juju.
- Familiarity with the Python programming language, Object-Oriented Programming, event handlers.
- Understanding of Kubernetes fundamentals.


**What you'll do:**

<!--
- {ref}`Study your application <study-your-application>`
- {ref}`Set up your development environment <set-up-your-development-environment>`  
- Develop your charm:
    1. {ref}`Create a minimal Kubernetes charm <create-a-minimal-kubernetes-charm>`
    1. {ref}`Make your charm configurable <make-your-charm-configurable>`
    1. {ref}`Expose the version of the application behind your charm <expose-the-version-of-the-application-behind-your-charm>`
    1. {ref}`Integrate your charm with PostgreSQL <integrate-your-charm-with-postgresql>`
    1. {ref}`Preserve your charm's data <preserve-your-charms-data>`
    1. {ref}`Expose your charm's operational tasks via actions <expose-operational-tasks-via-actions>`
    1. {ref}`Observe your charm with COS Lite and set up cross-model integrations <observe-your-charm-with-cos-lite>`
    1. {ref}`Write unit tests for your charm <write-unit-tests-for-your-charm>`
    1. {ref}`Write scenario tests for your charm <write-scenario-tests-for-your-charm>`
    1. {ref}`Write integration tests for your charm <write-integration-tests-for-your-charm>`
    1. {ref}`Open a Kubernetes port in your charm <open-a-kubernetes-port-in-your-charm>`
    1. {ref}`Publish your charm on Charmhub <publish-your-charm-on-charmhub>`
-->


```{toctree}
:maxdepth: 1

set-up-your-development-environment
study-your-application
create-a-minimal-kubernetes-charm
make-your-charm-configurable
expose-the-version-of-the-application-behind-your-charm
integrate-your-charm-with-postgresql
preserve-your-charms-data
expose-operational-tasks-via-actions
observe-your-charm-with-cos-lite
write-unit-tests-for-your-charm
write-scenario-tests-for-your-charm
write-integration-tests-for-your-charm
open-a-kubernetes-port-in-your-charm
publish-your-charm-on-charmhub
```



(tutorial-kubernetes-next-steps)=
## Next steps

By the end of this tutorial you will have built a machine charm and evolved it in a number of typical ways. But there is a lot more to explore:

| If you are wondering... | visit...             |
|-------------------------|----------------------|
| "How do I...?"          | {ref}`how-to-guides` |
| "What is...?"           | {ref}`reference`     |
| "Why...?", "So what?"   | {ref}`explanation`   |