docker-development-youtube-series/kubernetes/fluxcd/README.md

# Introduction to Flux CD v2

## Create a kubernetes cluster

In this guide we we''ll need a Kubernetes cluster for testing. Let's create one using [kind](https://kind.sigs.k8s.io/) </br>

```
kind create cluster --name fluxcd --image kindest/node:v1.23.5
```

## Run a container to work in

### run Alpine Linux: 
```
docker run -it --rm -v ${HOME}:/root/ -v ${PWD}:/work -w /work --net host alpine sh
```

### install some tools

```
# install curl 
apk add --no-cache curl

# install kubectl 
curl -sLO https://storage.googleapis.com/kubernetes-release/release/`curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt`/bin/linux/amd64/kubectl
chmod +x ./kubectl
mv ./kubectl /usr/local/bin/kubectl

```

### test cluster access:
```
/work # kubectl get nodes
NAME                    STATUS   ROLES    AGE   VERSION
fluxcd-control-plane   Ready    control-plane,master   3m26s   v1.23.5
```

## Flux CD 

### get flux command-line tool

Let's download the `flux` command-line utility. </br>
We can get this utility from the GitHub [Releases page](https://github.com/fluxcd/flux2/releases) </br>

It's also worth noting that you want to ensure you get a compatible version of flux which supports your version of Kubernetes. Checkout the [prerequisites](https://fluxcd.io/flux/installation/#prerequisites) page. </br>

```
curl -o /tmp/flux.tar.gz -sLO https://github.com/fluxcd/flux2/releases/download/v0.41.1/flux_0.41.1_linux_amd64.tar.gz
tar -C /tmp/ -zxvf /tmp/flux.tar.gz
mv /tmp/flux /usr/local/bin/flux
chmod +x /usr/local/bin/flux
```

Now we can run `flux --help` to see its installed

## Check our cluster

```
flux check --pre
```

## Documentation

As with every guide, we start with the documentation </br>
The [Core Concepts](https://fluxcd.io/flux/concepts/) is a good place to start. </br>

We begin by following the steps under the [bootstrap](https://fluxcd.io/flux/installation/#bootstrap) section for GitHub </br>

We'll need to generate a [personal access token (PAT)](https://github.com/settings/tokens/new) that can create repositories by checking all permissions under `repo`.  </br>

Once we have a token, we can set it: 

```
export GITHUB_TOKEN=<your-token>
```

Then we can bootstrap it using the GitHub bootstrap method

```
flux bootstrap github \
  --owner=marcel-dempers \
  --repository=docker-development-youtube-series \
  --path=kubernetes/fluxcd/repositories/config/clusters/dev-cluster \
  --personal \
  --branch fluxcd-2022

flux check

# flux manages itself using GitOps objects:
kubectl -n flux-system get GitRepository
kubectl -n flux-system get Kustomization
```

Check the source code that `flux bootstrap` created 

```
git pull origin <branch-name>
```

# Repository structure 

https://fluxcd.io/flux/guides/repository-structure/

* Mono Repo
* Repo per team
* Repo per app

```
- apps
  - example-app-1
  - example-app-2
- infrastructure
  - ingress-nginx
  - monitoring
- clusters
  -dev-cluster
  -prod-cluster
```

## build our app

Let's say we have a microservice called `example-app-1` and it has its own GitHub repo somewhere. </br>
For demo, it's code is under `kubernetes/fluxcd/repositories/example-app-1/`

```
# go to our "git repo"
cd kubernetes/fluxcd/repositories/example-app-1
# check the files
ls

cd src
docker build . -t example-app-1:0.0.1

#load the image to our test cluster so we dont need to push to a registry
kind load docker-image example-app-1:0.0.1 --name fluxcd 
```

## setup our gitops pipeline

Now we will also have a "config" GitHub repo where configuration files for GitOps live.

```
cd kubernetes/fluxcd

# tell flux where our Git repo is and where the YAML is
# this is once off
# flux will monitor the example-app-1 Git repo for when any infrastructure changes, it will sync
kubectl -n default apply -f repositories/config/apps/example-app-1/gitrepository.yaml
kubectl -n default apply -f repositories/config/apps/example-app-1/kustomization.yaml

# check our flux resources 
kubectl -n default describe gitrepository example-app-1
kubectl -n default describe kustomization example-app-1

# check deployed resources
kubectl get all

kubectl port-forward svc/example-app-1 80:80

```

Now we have setup CD, let's take a look at CI </br>

## changes to our app

Once we make changes to our `app.py` we can build a new image with a new tag </br>

```
docker build . -t example-app-1:0.0.2

#load the image to our test cluster so we dont need to push to a registry
kind load docker-image example-app-1:0.0.2 --name fluxcd 

# update our kubernetes deployment YAML image tag
# git commit & git push to branch!
```

## deploy by updating manifest 

To update our app, we simply have to update the image tag in our kubernetes YAML
file and `flux` will sync it. </br>
This is generally the role of CI, where `flux` concern is mainly CD. </br>

Here is an example on [how to automate that](https://fluxcd.io/flux/use-cases/gh-actions-manifest-generation/) 

## deploy by image scanning

An alternative method is to use your CI to build and push a newly tagged image to your registry (same as first option) and use Flux image scanner to trigger the rollout instead of automating a commit to your config repo. </br>

We firstly need to enable image scanning as its not enabled by default. </br>
To do this we just need to re-bootstrap `flux` with an addition flag

```
flux bootstrap github \
  --owner=marcel-dempers \
  --repository=docker-development-youtube-series \
  --path=kubernetes/fluxcd/repositories/config/clusters/dev-cluster \
  --components-extra=image-reflector-controller,image-automation-controller \
  --personal \
  --branch fluxcd-2022
```
We need to create a image reigsitry credential where we will push our image:

```
kubectl -n default create secret docker-registry dockerhub-credential --docker-username "" --docker-password "" --docker-email test@test.com

```

We will need to tell Flux how to manage our image deployment

## add image policy and repository

```
kubectl -n default apply -f repositories/config/apps/example-app-1/imagerepository.yaml
kubectl -n default apply -f repositories/config/apps/example-app-1/imagepolicy.yaml

```

https://fluxcd.io/flux/guides/image-update/#configure-image-updates

## Build and push our app

```
docker build . -t aimvector/example-app-1:0.0.2
docker push aimvector/example-app-1:0.0.2

#see changes
kubectl describe imagerepository

```