Lifecycle Management with Helm

  • Each time we pull in a chart and install it, a release is created.

    • A release is a package or collection of Kubernetes objects.

      • The good thing about this system, is that upgrades, downgrades and uninstalls can be performed without touching other releases.

      • Each release can be managed independently, even if they are all based on the same chart.

  • How to install a specific version of a release, you can do:

helm install nginx-release bitnami/nginx --version 7.1.0

  • For example, if there are security vulnerabilities in a web app, have to make changes to more nginx objects. Or if a secret needs to be created for a while.

    • This can cause issues when tracking the changes.

  • Helm can automatically upgrade all objects with one command.

  • Use the kubectl describe pod <pod_name> to find out more about the version of the image in use.

  • In order to upgrade, we tell helm we need to upgrade and then specify the chart that it is released on.

  • We run the following command: helm upgrade nginx-release bitnami/nginx

  • During the upgrade process, the old pod is destroyed and a new one is created.

    • Then we can see the new version of the pod by finding the name, then check the kubectl describe.

  • helm can keep track of its current state and past states.

  • Run the helm list commands to show the current releases.

  • Run the helm history <nginx-release (for example)> to see more information about a particular release.

  • Helm allows for rollback.

  • To rollback to a previous revision, run helm rollback <nginx-release (for example)> <revision number>

    • Technically however it does not go back to revision 1, it creates a new revision called revision 3.

      • There will be a note in the description of what is changed.

  • helm cannot upgrade everything without administrative passwords.

  • Depending on the app, helm may need access to passwords (of a database for example), it order to rollback and make changes.

  • helm backs up the declaration files or persistent objects.

  • Regarding rollbacks and data, a rollback won’t restore the data.

    • For example, a MySQL database. The pods will be rolled back, however the actual database, its data will remain the same.

  • There are options to take consistent backups of a database before a rollback, these are done by chart hooks.

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