How to operate during DSP contract negotiations

[jima-r20]

Hello.

I am looking for a mechanism that allows the data provider to manually check the contract negotiations before the CN state is “AGREED” and then make a contract agreement (i.e., continue the DSP process).

Is it possible for EDC to implement such a mechanism?

I understand from the Contributors Manual that it is not possible to directly change the state, but I am wondering if it is possible to pause the CN, visually check the request contents, and if there are no problems, continue processing.

• they cannot be changed by the user directly
• users can only decline, terminate or cancel them

[jimmarino]

It sounds like you are trying to create a manual workflow. A PendingGuard can be implemented to do this, cf. #4460.

[jima-r20]

Oh, Thanks!
I think what I wanted to know is probably about PendingGuard!

However, I am not sure how to use this...
For example, when ContractNegotiation is REQUESTED, how do I implement pending to run an external API service (e.g. https://example.com) and continue or terminate the contract negotiation based on the results ? What is the best way to do this?

I understand that I need to implement a ContractNegotiationPendingGuard, but I don't know how to register an implementation class.

I would appreciate it if you could give me some tips in my ignorance.

[jimmarino]

There are two approaches.

The first is to call out to the service, immediately return a result, and change the entity state accordingly. The second is to call the service, return, and the result returned in a callback. The callback allows for an async result to be passed back at a future time. When the result is received, you will need to use a CommandHandler to transition the entity.

Registering implementation classes as extensions is extensively documented, so I will not go over that here.

[ndr-brt]

In addition there's the DR about how guards were implemented:
https://github.com/eclipse-edc/Connector/tree/bfe92d537217474f9e7c8e4d8758b16714ec3f0e/docs/developer/decision-records/2023-07-20-state-machine-guards

unfortunately this hasn't been documented in the website. I created an issue for this: eclipse-edc/eclipse-edc.github.io#75