Define how device-specific parameter values can be provided

[ajcraig]

Feature description

Goal: Define how device-specific parameter values can be provided to the WFM to ensure the application's deployment specification can utilize.

Category

• Application Description File
• Device platform configuration

Provide adequate technical acceptance criteria(s) associated with this feature below:

• Define how the device can report the device specific parameters
• Define how the application instances can be tied to these parameters for usage during deployment
• Describe format and where it is to be included in our current Margo defined artifacts
• Ensure the solution covers Helm lookup functionality.
• This feature applies to both kubernetes, docker, and custom specific runtimes.

Although not required, it is highly encouraged to provide feature use-cases below:

Without some way to indicate that a parameter's value should be provided by the device, the customer will need to be able to find the value to use and manually set the parameter when installing the application. While this may be easy for things like Hostname, finding other values, such as the default storage class name for persistent volumes on the device, is not so easy for a customer to find.

Additional information

• This becomes a much bigger issue if it is decided that Margo does not require the Helm Lookup function be supported (item 13 below) because this means Helm charts would not be able to look up existing values using the Kubernetes API

** Proposed solution **

• We work with the TWG to define a minimal set of expressions for GA1 that can be used in the parameter definition (e.g., {cluster.hostname}, {cluster.storageClass}) to indicate these values should be provided by the device
• Before installing the application, the device evaluates the expression to set the parameter's value
• For cases where the application vendor and device vendor are working together, they have the freedom to define their own expressions

** Additional Comments **
Consider a proposal for specific device supplied parameters. Explore helm capability to fetch resources at runtime (e.g. could use to fetch hostname or properties from a secret).

Storm (SIEMENS): This also applies to the Docker variant, doesn't it?

Storm (SIEMENS): What about a mechanism analogously to "device capabilities" that is introspectable and yields a set of key=value pairs? Avoids hard-coding (which is sensible for mandatory/common parameters). GA1 can start with this set of mandatory parameters and then be extended?