Distributed workflows for Guardian policy chain

[anvabr]

Problem description

2075 introduced the capability of linking independently executed policies (or modules) into a chain, the execution of each link in such chains can be automatically triggered by the previous link via publishing a document of the type which has been configured to be the 'source' for the link. This allows for the creation of the distributed policy chains, where 'execution' can be passed from one Guardian instance to another via publishing the corresponding artefacts.

However practical execution of most real-world Policies requires more powerful coordination features such as requests (approvals etc), events, and notifications which exists within a single policy instance but cannot be visible externally.

Requirements

• Revamp the implementation of Guardian workflow coordination features to 'externalise' them such that from the point of view of individual users (defined in the policy) it would not matter whether the policy chain in its entirety is run on a single instance or across multiple instances
• Adapt, if necessary, policy definition language to make it compatible with the distributed view of policy execution
• Make sure Tools, Modules etc are compatible with distributed policy chains

Definition of done

• The implemented functionality is capable of delivering on requirements specified above
• Corresponding documentation set is created
• Some of the policies packaged with Guardian are implemented as policy chains with instructions on how they could be combined into a distributed workflow

Acceptance criteria

Real-world policies can be implemented/deployed as chains across multiple guardian instances and operated by users conveniently as if these were executed on the same instance.

[MarcAntoineLebourgeois]

I share the needs of Alex here. Between Straatos <> Evercity, we have a case in which each of use own a guardian instance. Ours is used for doing the proper collection and validation workflow of a policy, including third party like VVB. Evercity's one has a complementary module of the same policy adding a Carbon Forwards capacity. At current stage, the VVB validation could trigger a "data migration" towards the second instance but we lost the view/control of the workflow. Conceptually, the proposition of Alex could help us having one single workflow shares by two guardian instances, coming closer to the business perspective.