Problem: Dealing With the Outside World (we need to get something done in the outisde world)

[ylorph]

As in ... some call needs to be done to say a payment gateway

Options:

• Requested Patterns (@edblackburn or @MerrionComputing term, I like it )

[patryk-marcin-zielinski]

Is there any referential implementation of requested pattern? I would assume this pattern is part of the infrastructure? (or this is an incorrect assumption?) How the result of that communication could be express in a domain? (probably event?)

[ylorph]

Not necessarily infra , it's always dependent on the type of process behind the scene,
=> think of web sites where you reserve a spot & they tell you at one point in time "please fill in the rest of the details within 15min so that we can confirm your spot" (airlines, bookings, ......)

[patryk-marcin-zielinski]

Ok I think I understand do we have any referential implementation?

[MerrionComputing]

There are abstract entities in lots of businesses that do represent a form of saga pattern (with names like "booking" or "transaction" etc.) and for these the state of them depends on what is going on with external (to them) factors. By having a x requested event you can get the state of the saga in terms of "was everything I need done completed" because if the number of requests exceed the number of responses then we are waiting for something.

Dealing with non response to a request is an issue though - do you go with a timeout on the abstract entity (source) side and add a "No response to request" event which then triggers the compensating actions required to undo the saga-style entity?