I am working on a JAVA program that has to run a very simple workflow made of 5 tasks and executed one by one:

Workflow:   Task(A) -> Task(B) -> Task(C) -> Task(D) -> Task(E)
                                  -------    -------

This workflow is launched, every time that my program receives an input

The only difficulty I have is that the workflow can block at 3rd and 4th tasks

Indeed,

• Task(C) calls/uses Service(C) that can be momentarily down
• Task(D) calls/uses Service(D) that also can be momentarily down

Here is the behavior that I want to reach:

• when a service is down (Service(C) or Service(D)) the current workflow should interrupt
• when a new input is received while a service is down (Service(C) or Service(D)), all tasks of the workflow should be run until the blocked task
• when a down service becomes up once again (and the task unblocks), all interrupted executions should immediately restart

For sure I can develop my own framework to reach what I need but I would like to use an existing framework (preferably in the JDK) in order to benefit from something robust and proven

I found that since Java 8 (very old: sorry for not being up to date) Java provides CompletableFuture that seems to be very powerful… however, I’m not yet very comfortable with it

• is it possible to reach my target behavior with JAVA CompletableFuture?
• or should I use a different Framework? If so, which one?
• whatever is the answer, I would strongly appreciate light examples

Thank you for helping