App Revisions

This topic describes app revisions and provides procedures for working with them.

For additional information, see Revisions in the Cloud Foundry API (CAPI) documentation.

Note: CAPI v3 is the recommended API version for revisions. While revisions work with CAPI v2, there are several inconsistencies. For example, revision descriptions for apps with multiple processes may be inaccurate because CAPI v2 does not support apps with multiple processes. Additionally, pushing an app for the first time with revisions in CAPI v2 creates two revisions.

Note: The App Revisions API is experimental, and future releases may have breaking changes.

Overview

A revision represents code and configuration used by an app at a specific time. It is a CAPI object that can contain references to a droplet, custom start command, and environment variables. The most recent revision for a running app represents code and configuration currently running in Ops Manager.

Some use cases for revisions include:

Viewing revisions for an app: This can help you understand how your app has changed over time.
Rolling back to a previous revision: This allows you to deploy a version of the app that you had running previously without needing to track that 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.

Events that Trigger Revisions

Revisions are generated automatically through these events:

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

By default, CAPI retains a maximum of 100 revisions per app.

Revision Descriptions

Each revision includes a description of what changed in your app at the time the revision was created. The description includes one or more of these descriptions:

Process type removed
New process type added
Rolled back to revision X
Custom start command removed
Custom start command updated
Custom start command added
New environment variables deployed
New droplet deployed

Droplet Storage Considerations

By default, Ops Manager retains the five most recent staged droplets in its droplets bucket. This means that you can roll back to revisions as long as they are using one of those five droplets. Not all revisions include a change in droplet.

Operators can configure Ops Manager to retain more droplets if necessary using the Maximum staged droplets per app field in the File Storage pane of the VMware Tanzu Application Service for VMs (TAS for VMs) tile.

View Revisions

This section describes how to use CAPI endpoints for viewing revisions.

List Revisions for an App

To list revisions for an app:

Retrieve the GUID of the app by running:
```
cf app APP-NAME --guid
```
Where APP-NAME is the name of your app.
Run:
```
cf curl /v3/apps/GUID/revisions
```
Where GUID is the GUID you retrieved in the previous step.

List Deployed Revisions for an App

Deployed revisions are revisions linked to started processes in an app. To list deployed revisions:

Retrieve the GUID of the app by running:
```
cf app APP-NAME --guid
```
Where APP-NAME is the name of your app.
Run:
```
cf curl /v3/apps/GUID/revisions/deployed
```
Where GUID is the GUID you retrieved in the previous step.

Retrieve a Revision

To retrieve a revision:

Run:
```
cf curl /v3/revisions/GUID
```
Where GUID is the GUID of the revision.

Roll Back to a Previous Revision

To roll back to a previous revision:

Retrieve the GUID of the app by running:
```
cf app APP-NAME --guid
```
Where APP-NAME is the name of your app.
Retrieve the GUID of the revision. For more information, see Retrieve a Revision.

Create a deployment using CAPI by running:

cf curl v3/deployments \
-X POST \
-d '{
  "revision": {
    "guid": "REVISION-GUID"
  },
  "relationships": {
    "app": {
      "data": {
        "guid": "APP-GUID"
      }
    }
  }
}'

Where:

REVISION-GUID is the GUID of the revision.
APP-GUID is the GUID of the app.

Add Metadata to a Revision

To add metadata to a revision, see Add Metadata to an Object.

Disable Revisions for an App

CAPI enables app revisions by default. To disable revisions for an app, you must manually turn them off.

To disable revisions for an app:

Retrieve the GUID of the app by running:
```
cf app APP-NAME --guid
```
Where APP-NAME is the name of your app.

Run:

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

Where GUID is the GUID you retrieved in the previous step.