How to Reset a Cloud Foundry Droplet to a Previous Version and download the droplet code

In the fast-paced world of software development, rolling out updates is a routine task. However, not every update goes as planned. Sometimes, a newly deployed version of an application introduces unforeseen issues, and rolling back to a previous stable version becomes essential. Cloud Foundry (CF) makes this process straightforward with its built-in support for managing application droplets. In this post, we’ll walk through the steps to reset a CF droplet to a previous version and download a droplet.

What is a Droplet in Cloud Foundry?
A droplet is an immutable snapshot of your application code, its dependencies, and the runtime environment created during the staging process. When you deploy an app to CF, it stages the app, generates a droplet, and assigns it to the app’s instances. Each droplet represents a specific version of your application. CF keeps up to 5 previous droplets in a staged state. Older droplets are marked as expired.

Why Reset a Droplet?
You might want to reset a droplet to a previous version for various reasons:

The new version of the application has critical bugs or performance issues.A misconfiguration was introduced in the latest deployment.There’s a need to quickly restore service stability.

Prerequisites
Before resetting or downloading a droplet, ensure the following:

Install cf cli if it is not already installed. You can download it from the official cf site.Ensure you have access to the Cloud Foundry CLI (cf command-line tool).Make sure you have the necessary permissions to view application history and make updates.Verify that the previous droplets are available and listed in the app’s droplet history.Install the multiapps plugin, if not already installed, using the following command:

cf install-plugin multiapps

Step-by-Step Guide to Reset a Droplet

1. Login to CF
Login to CF using the following command

cf login -u <userId> -a <API_URL>

Or use Single Sign-On (SSO):

cf login -u <userId> -a <API_URL> –sso

Replace <userId> and <API_URL> with your user ID and the public API endpoint

2. List Available Droplets
Retrieve the list of available droplets for your application:

cf droplets <app-name>

This command will display all droplets associated with the application, including their GUID, creation date, and state. Identify the GUID of the droplet you want to reset.

3. Change the Current Droplet
Change the current droplet to a previous one using the following command:

cf set-droplet <app-name> <guid-droplet>

Replace <guid-droplet> with the GUID of the desired droplet.

4.Restart the App
After changing the droplet, restart the application:

cf restart <app-name>

This step is mandatory to apply the changes. After restarting, verify the current droplet with:

cf droplets <app-name>

Downloading a Droplet

Downloading a droplet allows you to retrieve a specific version of your application for debugging, analysis, or redeployment.

1. List Available Droplets
Retrieve the list of available droplets for your application:

cf droplets <app-name>

Identify the GUID of the droplet you want to download.

2. Download the Droplet
Use the cf curl command to download the droplet:

cf curl /v3/droplets/<droplet-guid>/download –output <filename>

Replace <droplet-guid> with the GUID of the desired droplet.
Replace <filename> with the desired file name for saving the droplet locally (e.g., my-droplet.tar).

Example:

cf droplets my-app cf curl /v3/droplets/abc12345-6789-def0-ghij-klmnopqrstuv/download –output my-app-droplet.tar

The downloaded file will be a tarball containing the application code, dependencies, and runtime environment.

Conclusion
Resetting a droplet in Cloud Foundry is a lifesaver when you need to revert to a stable version of your application quickly. Additionally, downloading droplets and examining can provide deeper insights into your application’s state for debugging or analysis. 

Have you faced challenges with rolling back or downloading droplets in Cloud Foundry? Share your experiences and solutions!

​ In the fast-paced world of software development, rolling out updates is a routine task. However, not every update goes as planned. Sometimes, a newly deployed version of an application introduces unforeseen issues, and rolling back to a previous stable version becomes essential. Cloud Foundry (CF) makes this process straightforward with its built-in support for managing application droplets. In this post, we’ll walk through the steps to reset a CF droplet to a previous version and download a droplet.What is a Droplet in Cloud Foundry?A droplet is an immutable snapshot of your application code, its dependencies, and the runtime environment created during the staging process. When you deploy an app to CF, it stages the app, generates a droplet, and assigns it to the app’s instances. Each droplet represents a specific version of your application. CF keeps up to 5 previous droplets in a staged state. Older droplets are marked as expired.Why Reset a Droplet?You might want to reset a droplet to a previous version for various reasons:The new version of the application has critical bugs or performance issues.A misconfiguration was introduced in the latest deployment.There’s a need to quickly restore service stability.PrerequisitesBefore resetting or downloading a droplet, ensure the following:Install cf cli if it is not already installed. You can download it from the official cf site.Ensure you have access to the Cloud Foundry CLI (cf command-line tool).Make sure you have the necessary permissions to view application history and make updates.Verify that the previous droplets are available and listed in the app’s droplet history.Install the multiapps plugin, if not already installed, using the following command: cf install-plugin multiapps  Step-by-Step Guide to Reset a Droplet1. Login to CFLogin to CF using the following command cf login -u <userId> -a <API_URL> Or use Single Sign-On (SSO): cf login -u <userId> -a <API_URL> –sso Replace <userId> and <API_URL> with your user ID and the public API endpoint2. List Available DropletsRetrieve the list of available droplets for your application: cf droplets <app-name> This command will display all droplets associated with the application, including their GUID, creation date, and state. Identify the GUID of the droplet you want to reset.3. Change the Current DropletChange the current droplet to a previous one using the following command: cf set-droplet <app-name> <guid-droplet> Replace <guid-droplet> with the GUID of the desired droplet.4.Restart the AppAfter changing the droplet, restart the application: cf restart <app-name> This step is mandatory to apply the changes. After restarting, verify the current droplet with: cf droplets <app-name>  Downloading a DropletDownloading a droplet allows you to retrieve a specific version of your application for debugging, analysis, or redeployment.1. List Available DropletsRetrieve the list of available droplets for your application: cf droplets <app-name> Identify the GUID of the droplet you want to download.2. Download the DropletUse the cf curl command to download the droplet: cf curl /v3/droplets/<droplet-guid>/download –output <filename> Replace <droplet-guid> with the GUID of the desired droplet.Replace <filename> with the desired file name for saving the droplet locally (e.g., my-droplet.tar).Example: cf droplets my-app cf curl /v3/droplets/abc12345-6789-def0-ghij-klmnopqrstuv/download –output my-app-droplet.tar The downloaded file will be a tarball containing the application code, dependencies, and runtime environment.ConclusionResetting a droplet in Cloud Foundry is a lifesaver when you need to revert to a stable version of your application quickly. Additionally, downloading droplets and examining can provide deeper insights into your application’s state for debugging or analysis. Have you faced challenges with rolling back or downloading droplets in Cloud Foundry? Share your experiences and solutions!   Read More Technology Blogs by SAP articles 

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