Introduce syntax for specifying max number of pending events on delayed connections and actions

[erlingrj]

In reactor-uc we statically allocate all events which means that there is a bound on the number of outstanding events that can be buffered for each action and eached delayed/physical connection.

We need a syntax for specifying these bounds.

Proposal 1 for Actions: Change LF syntax

reactor R {
  logical action a(0, 10 msec, defer, 15) // We add it as an LF argument together with a policy
}

Proposal 2 for Actions: Use annotation

reactor R {
  @num_events=15
   logical action a(0, 10 msec)

  @buffer=15
   logical action a(0, 10 msec)
   
   @max_pending_events=15
   logical action a(0, 10 msec)
}

Proposals 3 for connections: Change LF syntax

src.out -> sink.in after 100 msec buffer 15
src.out -> sink.in after 100 msec pending 15
src.out -> sink.in after 100 msec allocate 15

Proposals 4 for connections: Use annotations

@num_events=15
src.out -> sink.in after 100 msec

@buffer=15
src.out -> sink.in after 100 msec

@max_pending_events=15
src.out -> sink.in after 100 msec

[erlingrj]

@tanneberger what do you think?

[edwardalee]

Without a strong preference, I like:

   @max_pending_events=15
   logical action a(0, 10 msec)

and

@buffer=15
src.out -> sink.in after 100 msec

[erlingrj]

Thanks, I also realize that we need a "policy" for buffer overflows, either we "drop" the event, or we "replace" an existing. We might also need to specify which event to replace, I think either you want to replace to earliest event, the last event, or the event with the closest tag.