How to update stack to cflinuxfs4 in SAP BTP Application [CAP using Postgres database]

I recently came across a helpful blog post by Veli, Beyhan regarding the deprecation of the Cloud Foundry cflinuxfs3 stack and the need to migrate to cflinuxfs4.

In my case , our fiori applications on BTP is using the Postgres database instance  . To deploy and create postgrace database artifacts , along with nodejs buildpack , apt-buildpack (https://github.com/cloudfoundry/apt-buildpack) is also neccessary .

Therefore to change the stack to cflinuxfs4 for Postgres, it is not possible to change it directly

from the BTP Cockpit . Why ? 

Because In this case , we also need to check if the apt-buildpack version that we use is compatible with the new stack cflinuxfs4 or we need to upgrade.

Stack Change Option – BTP Cockpit

The steps we took for the change –

1. Check for the compatible apt-buildpack version .We used v0.2.10 , but found this version was not compatible with stack cflinuxfs4. 
2. The version compatible with cflinuxfs4 is v0.3.0 .
3. Changes in mta.yaml
   1. In the module section with name – <customname>-db-deployer . Adding parameters  to db-deployer section also affects the service.
      1. parameters
         1. stack : cflinusfs4
         2. buildpacks :
            1. -nodejs_buildpack
            2. -https://github.com/cloudfoundry/apt-buildpack#v0.3.0

4. Before deploying this change , the postgres db instance needs to be deleted for the change to affect.  Therefore if the change has to be deployed  in the acceptance or the production environment , take a backup of the data as deletion of db instance means loss of data .

BTP – Postgres db instance

5. Once the change is deployed , the service and deployer application in BTP reflects the change of stack cflinusfs4.

Conclusion : To change stack for postgres db always check if apt-buildpack compatible version and before deploying the changes to productive environment take a backup of the data in the postgres db else there is a data loss as mentioned in Step 4.

References –

Deprecation of Cloud Foundry Stack cflinuxfs3 and Migration to cflinuxfs4

How to update stack to cflinuxfs4 in SAP BTP Cloud Foundry Applications [CAP , NodeJS ,Java]

Thanks in advance to everyone for reading the blog !!.