Running cf push sub-step commands

The Cloud Foundry Command Line Interface (cf CLI) includes commands that provide detailed control over app pushes. When you use these commands, you can follow only some steps of the cf push procedure or you can perform specific actions between the steps that are normally part of running cf push.

Here are some example use cases for the sub-step commands:

Updating a third-party system before staging an app
Retrying failed stagings without incurring downtime
Calling external services to report audit data during push
Scanning a droplet before deploy
Integrating with a change request system
Running droplets built on a different Cloud Foundry deployment

To support these custom push workflows, Cloud Foundry divides apps into smaller building blocks.

The following table describes the building blocks as resources and lists the command associated with each one.

For information about using these commands, see Example workflows.

Resource	Description	Commands
App	The top-level resource that represents an app and its configuration. For more information, see Apps in the CAPI documentation.	`cf app` `cf apps` `cf create-app`
Package	The source code that makes up an app. For more information, see Packages in the CAPI documentation.	`cf create-package` `cf packages`
Build	Staging the app. Creating a build combines a Package with a Buildpack and builds it into an executable resource, called a Droplet. For more information, see Builds in the CAPI documentation.	`cf stage-package`
Droplet	An executable resource that results from a Build. For more information, see Droplet in the CAPI documentation.	`cf download-droplet` `cf droplets` `cf set-droplet`
Manifest	A file used when pushing your app to apply bulk configuration to an app and its underlying processes. For more information, see Space Manifest in the CAPI documentation.	`cf apply-manifest` `cf create-app-manifest`

Example workflows

The following sections describe example workflows for working with the cf push sub-step commands.

Push an app using sub-step commands

This example workflow describes how to push an app using sub-step commands instead of cf push.

Create your app with cf CLI:
```
cf create-app APP-NAME
```
Where APP-NAME is the name you give your app.
From your app directory, create a package for your app.
```
cf create-package APP-NAME
```
Where APP-NAME is the name of your app.

Locate and copy the package guid from the output of an earlier step or by using the cf packages command. See the following example output:

Uploading and creating bits package for app APP-NAME in org test / space test as admin...
 package guid: 0dfca85a-8ed4-4f00-90d0-3ab08852dba8
 OK

Stage the package you created:
```
cf stage-package APP-NAME --package-guid PACKAGE-GUID
```
Where:
- APP-NAME is the name of your app.
- PACKAGE-GUID is the package GUID you recorded in an earlier step.

Locate and copy the droplet guid from the output of an earlier step or by using the cf droplets command. See the following example output:

Staging package for APP-NAME in org test / space test as admin...
...
Package staged
 droplet guid: f60d3464-415a-4202-9d40-26a70373a487
 state: staged
 created: Mon 25 Sep 16:37:45 PDT 2018

Assign the droplet to your app:
```
cf set-droplet APP-NAME DROPLET-GUID
```
Where:
- APP-NAME is the name of your app.
- DROPLET-GUID is the droplet GUID you recorded in an earlier step.
Start your app:
```
cf start APP-NAME
```
Where APP-NAME is the name of your app.

Roll back to a previous droplet

This example workflow describes how to roll back to a previous droplet used by your app. You might want to use this, for example, if you update your app and it has a bug that causes it to fail.

List the droplets for your app:
```
cf droplets APP-NAME
```
Where APP-NAME is the name of your app.

In the output, locate and copy the second-to-last GUID.

In the following example, this is 66524145-5502-40e6-b782-47fe68e13c49.

Listing droplets of app APP-NAME in org test / space test as admin...

guid state created
    66524145-5502-40e6-b782-47fe68e13c49 staged Mon 25 Sep 16:37:34 PDT 2018
    0677ad93-9f77-4aaa-9a6b-44da022dcd58 staged Mon 25 Sep 16:44:55 PDT 2018

Stop your app:
```
cf stop APP-NAME
```
If you wish to avoid incurring downtime when changing your droplet, consider using Rolling deployments instead of stopping and starting your app.
Set the app to use the previous droplet:
```
cf set-droplet APP-NAME PREVIOUS-DROPLET-GUID
```
Where:
- APP-NAME is the name of your app.
- PREVIOUS-DROPLET-GUID is the droplet GUID you recorded in an earlier step.
Start your app:
```
cf start APP-NAME
```
Where APP-NAME is the name of your app.

Downloading and uploading droplets

This example workflow describes how to download a built droplet and then push it to an app. You might want to use this for building apps in one location and then deploying it elsewhere. For instance, you might use this to promote built apps from pre-production environments to production environments without having to re-build the app.

Download the current droplet for your app:
```
cf download-droplet APP-NAME --path PATH
```
Where APP-NAME is the name of your app and PATH is the file path to download the droplet to.
Log in to the desired Cloud Foundry environment and target the organization and space where you want to run the droplet you downloaded.
Push a new or existing app with the downloaded droplet:
```
cf push APP-NAME --droplet PATH
```
Where APP-NAME is the name of your app and PATH is the file path to the downloaded droplet.