Sveltos: Automate Configuration Updates for Kubernetes Applications
Tags: kubernetes, opensource, management, showdev
Published: 2023-08-10 10:18:11

ConfigMaps and Secrets are Kubernetes resources designed to decouple configuration details from application code, fostering a clear separation between configuration data and the application logic. This separation yields several compelling advantages, making the practice of mounting ConfigMaps and Secrets a crucial component of Kubernetes deployments.

1. **Configuration Flexibility**: Applications often require various configuration settings to function optimally across different environments. By mounting ConfigMaps, developers can modify configuration parameters without altering the application code. This not only streamlines the development process but also allows for on-the-fly adjustments, facilitating smooth transitions between development, testing, and production environments.
2. **Enhanced Security**: Secrets, such as sensitive authentication tokens, passwords, and API keys, contain critical information that must be safeguarded. Instead of hardcoding these sensitive details directly into the application code, they can be stored as Secrets and mounted into pods only when necessary. This mitigates the risk of inadvertent exposure and helps maintain a higher level of security.

## React to ConfigMap/Secret changes

[Sveltos](https://projectsveltos.github.io/sveltos/) is an open-source Kubernetes project to deploy add-ons in a multitude of Kubernetes cluster. Sveltos can also be instructed to watch for changes in ConfigMaps and Secrets and triggers rolling upgrades for the associated resources, ensuring that applications stay up-to-date.

To enable this functionality, simply set the **reloader** field to true in the ClusterProfile, as demonstrated in the following example YAML configuration:

```yaml
apiVersion: config.projectsveltos.io/v1alpha1
kind: ClusterProfile
metadata:
  name: nginx
spec:
  clusterSelector: env=fv
  reloader: true
  policyRefs:
  - name: nginx-data
    namespace: default
    kind: ConfigMap
  - name: nginx
    namespace: default
    kind: ConfigMap
```


![Sveltos: triggering rolling upgrades when ConfigMaps/Secrets change](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/lmuvio878hw0qb4p7niu.gif)

## How this works

Sveltos has the capability to monitor changes within ConfigMap and Secret resources and facilitate rolling upgrades for Deployments, StatefulSets, and DaemonSets.

1. When you create a ClusterProfile with the reloader field set to true, Sveltos [deploys all listed add-ons](https://medium.com/p/b9d4b48fc819) in each matching cluster. Sveltos will also get the list of Deployments, StatefulSets, and DaemonSets that are deployed because of the profile;
2. Sveltos will pass such list to the sveltos-agent running in each managed cluster. The sveltos-agent is responsible for monitoring ConfigMaps and Secrets for changes;
3. The sveltos-agent will build a list of ConfigMap and Secret instances that are mounted by Deployments, StatefulSets, and DaemonSets deployed by Sveltos. It then monitors those ConfigMaps and Secrets for changes. When a change is detected, the sveltos-agent will trigger a rolling upgrade for the affected resources.

By automating the configuration update process, Sveltos eliminates the need for manual intervention and reduces the risk of errors. This can help you to improve the reliability and security of your Kubernetes applications.

## 👏 Support this project

If you enjoyed this article, please check out the GitHub repo for the [project](https://github.com/projectsveltos). 

You can also [star 🌟 the project](https://github.com/projectsveltos/addon-controller) if you found it helpful.

The GitHub repo is a great resource for getting started with the project. It contains the code, documentation, and examples. You can also find the latest news and updates on the project on the GitHub repo.

Thank you for reading!