> I think that's the core of event-driven architecture that events drive the process, i.e. will trigger certain actions.
In an event-driven system, there is neither guarantee not expectation that an event will trigger an action; it might, but it might not. Events are simply a log [0] of "things" happening in various subsystems, published to various channels for other subsystems to ignore or act upon on their own terms.
Let say that we have two subsystems - A and B. When something happens on A, it will emit a corresponding event (e.g. SomethingHappened) to a specific channel (e.g. EventsFromA); if B is listening to that channel, it can "recognise" that event and initiate (i.e. "trigger") some action of its own.
However, if A explicitly wants B to do something, it's a command, i.e. a direct coupling by definition. As GP states, that is better handled as a direct request from A to B.
Theoretically, there is a possible scenario where A "knows" that a certain action needs to happen in the system, but does not know which subsystem has that capability, i.e. has no knowledge that B can do that. In that case it can "request" something to happen, e.g. by submitting an event like "UserCreationRequested"; however, there is no guarantee that any service will "see" that event and act upon it.
In an event-driven system, there is neither guarantee not expectation that an event will trigger an action; it might, but it might not. Events are simply a log [0] of "things" happening in various subsystems, published to various channels for other subsystems to ignore or act upon on their own terms.
Let say that we have two subsystems - A and B. When something happens on A, it will emit a corresponding event (e.g. SomethingHappened) to a specific channel (e.g. EventsFromA); if B is listening to that channel, it can "recognise" that event and initiate (i.e. "trigger") some action of its own.
However, if A explicitly wants B to do something, it's a command, i.e. a direct coupling by definition. As GP states, that is better handled as a direct request from A to B.
Theoretically, there is a possible scenario where A "knows" that a certain action needs to happen in the system, but does not know which subsystem has that capability, i.e. has no knowledge that B can do that. In that case it can "request" something to happen, e.g. by submitting an event like "UserCreationRequested"; however, there is no guarantee that any service will "see" that event and act upon it.
[0] https://engineering.linkedin.com/distributed-systems/log-wha...