during/spawn used not to add linkage assertions to its
initial-assertion set. In addition, if a spawned actor died in its
initial boot procedure, its initial assertions would never be visible.
These two problems interlocked to cause a space leak in during/spawn,
where monitoring facets would never be cleaned up.
This change does two things:
- adds linkage assertions to the initial-assertion set in during/spawn
- properly briefly signals initial-assertions even when a new actor
immediately crashes.
Together, these repair the space leak in during/spawn with a crashy
child startup procedure.
The `add-endpoint!` call is changed in two ways:
- the old `assertion-fn` has become `update-fn`, yielding both
an assertion *and* an optional handler, because if the handler
depends on a field which changes, previously the handler wasn't
being updated
- a new parameter, `dynamic?`, can be set to #f (it's usually #t)
to ensure that the assertion and skeleton-interest are calculated
only once ever, and are not connected to the dataflow machinery.
The first change makes it possible for the `(later-than (deadline))`
pattern, where `deadline` is a field, to work; the second change makes
`during` and `during/spawn` work correctly in the face of field
updates.
This repairs a bug regarding crashes in a new actor's boot-proc.
Previously, if boot-proc raised an exception, the initial assertions
would stick around forever. By changing adhoc-assertions to a bag
rather than a set, and putting the initial assertions in the bag, we
put them somewhere they are guaranteed to be processed during actor
termination, even when an exception is signalled during boot.
This is an API change wrt the previous Syndicate implementation:
assert!/retract! now have bag semantics, not set semantics. We can add
set-semantics APIs if we end up needing them, of course, layered on
top of the bag implementation.
Tony Garnock-Jones