Cancel contract negotiation within the process

[SebastianOpriel]

We know that an EDC extension can hook into events, e.g. shown via the old Clearing House or old Broker extension.

Is it possible to hook into the contract negotiation process and can the process be stopped via a hook, e.g. when some conditions are not met? Thus, going into terminated state, see here?

@ip312 @DanielHeiderMDS @jkbquabeck

[SebastianOpriel]

More info:
Related #605
Requirement: Usage Policy shall avoid auto transition between DSP negotiation states.

[tmberthold]

Maybe this API helps you with your use-case:
https://app.swaggerhub.com/apis/eclipse-edc-bot/management-api/0.2.1#/Contract%20Negotiation/terminateNegotiation

[ununhexium]

Quick PoC

https://github.com/sovity/edc-extensions/tree/823-cancel-contract-negotiation-within-the-process

With the guard, the negotiation process stops at the REQUESTED state:

DSP: Incoming catalog request.
[CONSUMER] ContractNegotiation CONTRACT1 is now in state INITIAL.
[CONSUMER] ContractNegotiation CONTRACT1 is now in state REQUESTING.
ContractNegotiation: ID CONTRACT. [Consumer] Send ContractRequestMessage message
DSP: Incoming ContractRequestMessage for contract negotiation process
[Provider] Contract offer received.
[PROVIDER] ContractNegotiation CONTRACT2 is now in state REQUESTED.
ContractNegotiation: ID CONTRACT. [Consumer] Send ContractRequestMessage message
[CONSUMER] ContractNegotiation CONTRACT1 is now in state REQUESTED.
[PROVIDER] ContractNegotiation CONTRACT2 is now in state REQUESTED.

And the process waits there.

[SebastianOpriel]

Awesome PoC! I think the process can be resumed and we would also be able to transition to terminated from what the code looks like or?

[ununhexium]

I should be resumable by changing the condition of the guard, yes.