Deploying and Managing Applications with Flux: A Technical Guide
Published: 2024-07-11 13:38:08

Flux is a powerful tool for managing and automating the deployment and configuration of applications and infrastructure within Kubernetes clusters. This blog post will delve into the technical aspects of deploying and managing applications using Flux, covering key concepts, setup, and configuration.

### Core Concepts

Before diving into the deployment and management of applications, it is essential to understand the core concepts of Flux. Flux is built around the principles of GitOps, which involves managing infrastructure and applications declaratively and version-controlled in a Git repository. This approach ensures that the deployed environment matches the state specified in the repository, promoting a declarative and version-controlled approach to operations.

### Setting Up Flux

To get started with Flux, you need a Kubernetes cluster and a GitHub personal access token with repository permissions. You can use Kubernetes kind for a local development environment. For production use, it is recommended to have a dedicated GitHub account for Flux and use fine-grained access tokens with the minimum required permissions.

### Installing the Flux CLI

The Flux command-line interface (CLI) is used to bootstrap and interact with Flux. You can install the CLI using Homebrew by running the following command:

```bash
brew install fluxcd/tap/flux
```

For other installation methods, refer to the CLI install documentation.

### Bootstrapping Flux

To bootstrap Flux onto your Kubernetes cluster, you need to export your GitHub personal access token and username:

```bash
export GITHUB_TOKEN=<your-token>
export GITHUB_USER=<your-username>
```

Then, run the bootstrap command:

```bash
flux bootstrap github \
  --owner=$GITHUB_USER \
  --repository=fleet-infra \
  --branch=main \
  --path=./clusters/my-cluster \
  --personal
```

This command creates a Git repository, adds Flux component manifests to the repository, deploys Flux components to your Kubernetes cluster, and configures Flux components to track the specified path in the repository.

### Cloning the Git Repository

Clone the `fleet-infra` repository to your local machine:

```bash
git clone https://github.com/$GITHUB_USER/fleet-infra
cd fleet-infra
```

### Adding a Podinfo Repository to Flux

Create a GitRepository manifest pointing to the podinfo repository’s master branch:

```bash
flux create source git podinfo \
  --url=https://github.com/stefanprodan/podinfo \
  --branch=master \
  --interval=1m \
  --export > ./clusters/my-cluster/podinfo-source.yaml
```

Commit and push the `podinfo-source.yaml` file to the `fleet-infra` repository:

```bash
git add -A && git commit -m "Add podinfo GitRepository"
git push
```

### Customizing Podinfo

To customize the podinfo application, you can create a Kustomization manifest:

```yaml
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: podinfo
  namespace: flux-system
spec:
  interval: 1m
  sourceRef:
    kind: GitRepository
    name: podinfo
  path: ./clusters/my-cluster
```

### Managing Applications with Flux

Flux provides a range of features for managing applications, including continuous deployment and progressive delivery. Continuous deployment involves automatically deploying code changes to production once they have passed through automated testing. Progressive delivery builds on continuous deployment by gradually rolling out new features or updates to a subset of users, allowing developers to test and monitor the new features in a controlled environment and make necessary adjustments before releasing them to everyone.

### Conclusion

In this technical guide, we have covered the key concepts, setup, and configuration of Flux for deploying and managing applications. Flux provides a powerful toolset for managing and automating the deployment and configuration of applications and infrastructure within Kubernetes clusters, promoting a declarative and version-controlled approach to operations. By following these steps, you can effectively [utilize Flux to streamline your application](https://platformengineers.io/blog/continuous-delivery-using-git-ops-principles-with-flux-cd/) management and deployment processes.