Defining MTA Extension Descriptors

The Multitarget Application (МТА) extension descriptor is a YAML file that contains data complementary to the deployment descriptor. The data can be environment or deployment specific, for example, credentials depending on the user who performs the deployment. The MTA extension descriptor is a YAML file that has a similar structure to the deployment decriptor. It follows the Multitarger Application Model structure with several limitations and differences. Normally, the extension descriptor extends the deployment descriptor but it is possible to build upon another extension descriptor, making an extension descriptors chain. It can add or overwrite existing data if necessary.

Several extension descriptors can be additionally used after the initial deployment.

Note:

The format and available options within the extension descriptor may change with newer versions of the MTA specification. You must always specify the schema version option when defining an extension descriptor to inform the SAP BTP which MTA specification version should be used. Furthermore, the schema version used within the extension descriptor and the deployment descriptor should always be the same.

In the examples below, we have a deployment descriptor, which has already been defined, and several extension descriptors.

Note:

Each extension descriptor is defined in a separate file with an extension .mtaext.

Deployment descriptor:

Example:

_schema-version: '3.1'
parameters:
  hcp-deployer-version: '1.0'
ID: com.example.extension
version: 0.1.0

resources:
  - name: data-storage
    properties:
      existing-data: value

The example above instructs SAP BTP to:

Validate the extension descriptor against the MTA specification version 3.1
Extend the com.example.extension deployment descriptor

The following is a basic example of an extension descriptor that adds data and overwrites data to another extension descriptor:

Example:

_schema-version: '3.1'
ID: com.example.extension.first
extends: com.example.extension

resources:
  - name: data-storage
    properties:
      existing-data: new-value
      non-existing-data: value

The above instructs SAP BTP to:

Extend the deployment descriptor by its ID com.example.extension
Validate the extension descriptor against the MTA specification version 3.1
Overwrite the data for the existing-data property
Add a new data called non-existing-data to the data-storage properties

The following is an example of another extension descriptor that builds upon the extension descriptor from the previous example:

Example:

_schema-version: '3.1'
ID: com.example.extension.second
extends: com.example.extension.first

resources:
  - name: data-storage
    properties:
      second-non-existing-data: value

The example above instructs the SAP BTP to:

Extend the first extension descriptor by its ID
Add a new data called second-non-existing-data to the data-storage properties
The examples above are incomplete. To deploy a solution, you have to create a deployment descriptor and an MTA archive.

What is possible to do with an extension descriptor?

You can do the following using an extension descriptor:

Add new data in properties and parameters on module level, resource level, provided section level and required section level
Overwrite an existing data (in depth) in modules, resources, parameters, properties, provides, requires sections. This depends on the parameter or property metadata overwritable. See Metadata for Properties and Parameters.
As of schema version 3.xx, by default parameters and properties are overwritable and optional. If you want to make a certain parameter or property non-overwritable or required, you need to add specific metadata. See Metadata for Properties and Parameters.

You cannot use an extension descriptor to:

Add new entities such as modules or resources
Change module or resource type
Alter read-only (system) parameters
Add new provided or required dependencies
Change the processing order of modules and resources with deployed-after and processed-after parameters