App Revisions

App revisions represent code and configuration used by an app at a specific point in time. The latest app revision represents the code and config that are currently running in your app.

Note that this feature is currently in Beta.

Why would I use App Revisions?

You might use revisions if:

  • You want to view revisions for an app: This can help you understand how your app has changed over time.
  • You want to roll back to a previous revision: You can redeploy an older version of the app without needing to track its previous state yourself or have multiple apps running. When you create a deployment and reference a revision, the revision deploys as the current version of your app.

When is a Revision Triggered?

Revisions are triggered automatically whenever the following events occur:

  • A new droplet is created for an app
  • An app’s environment variables are changed
  • A custom start command for an app is added or changed
  • An app rolls back to a prior revision

By default the Cloud Foundry API retains a maximum of 100 revisions per app.

List the Revisions on an App

To list the revisions for an app, we need to retrieve that app’s guid and then perform a cf curl against the API.

Let’s take a look at the revisions for the training-app.

cf revisions training-app

Whenever a new revision is created, the details of the event that triggered that revision are included in its description field. For example, say you update an environment variable with cf set-env and then restart the app in question. The revision would then include a description similar to:

"New droplet deployed. New environment variables deployed."

The currently deployed revision will be tagged with (deployed). Deployed revisions are revisions linked to started processes in an app

Roll Back to a Previous Revision

To roll back to a previous revision, you’ll need the revision number from the revision column. Pick a previous revision and rollback:

cf rollback training-app --version <REVISION_NUMBER>

Disable Revisions for an App

App revisions are enabled by default. If you want to disable revisions for an app, you can manually turn them off using cf curl:

cf curl /v3/apps/<APP-GUID>/features/revisions -X PATCH -d '{ "enabled": false }'

Try disabling app revisions for the training app and then trying to select another revision.

You can re-enable app revisions by amending the cf curl command slightly.

cf curl /v3/apps/<APP-GUID>/features/revisions -X PATCH -d '{ "enabled": true }'