Given it's a fairly simple yet useful abstraction, it makes sense to
offer this sub-sys alongside the core `tractor` runtime lib.
Without going into extreme detail on the impl changes (it'll come in
the commit that moves to the other repo) here is the high level summary:
------ - ------
- rename `Services` -> `ServiceMngr` and use an factory `@acm`
to guarantee a single-instance-per-actor using a niche approach for a
singleton object using a default keyword-arg B)
- the mod level `open_service_mngr()` and `get_service_mngr()` are the
new allocation/access API.
- add a `ServiceMngr.start_service()` method which does the work of both
spawning a new subactor (for the daemon) and uses its portal to start
the mngr side supervision task.
- open actor/task nurseries inside the `@acm` allocator.
Adjust other dependent subsystems to match:
------ - ------
- use `open_service_mngr()` when first allocated in `open_pikerd()`.
- use `get_service_mngr()` instead of importing the class ref inside
`.service.maybe_spawn_daemon()`, `.brokers._daemon.spawn_brokerd()`
and `.data._sampling.spawn_samplerd()` using a `partial` to pack in
the endpoint ctx kwargs (unpacked inside `.start_service()` XD).
Since service daemon actors may be cancelled remotely by clients (who
maybe also requested said daemon-actor's spawn in the first place) we
specifically ignore `tractor.ContextCancelled`s from the `ctx.wait()`
inside `Services.start_service_task()` to avoid crashing the service
mngr, and thus for now `pikerd`, (which **does** happen now due to
updated and more explicit remote cancellation semantics implemented in
`tractor`) since the `.canceller` field is not going to match the
`pikerd` uid in such cases!
This explicit check makes sense since the `Services` mngr is built to
allow remote requests to "spawn-n-supervise service actors" where the
services can remain persistent but also cancelled later as requested. We
may want to consider only allowing cancellation by actors who requested
spawn in the future tho?
Also change to more explicit imports to `tractor` types for annots
throughout the sub-pkg.
Allows for using the `Services.cancel_service()` api for explicit
cancellation in tests and eventually for remote teardown. Change
`.start_ahab()` to an `@acm` `start_ahab_service()` and just yield back
the same values we were returning prior. Also fix the logging (level) to
actually reflect what's passed in - we weren't using the correct name
/ instance from the `.sevice` subpkg..
If you want a sub-actor to write console logs (with the right level) the
`get_console_log()` call has to be made somewhere during service task
startup. Previously this wasn't well formalized nor used (depending on
daemon) so passing `loglevel` to the service's root-task-endpoint (eg.
`_setup_persistent_brokerd()`) encourages that the daemon's logging is
configured during init according to the spawner's requesting logging
config. The previous `get_console_log()` call happening inside
`maybe_spawn_daemon()` wasn't actually doing anything in the target
daemon XD, so obviously remove that and instead passthrough loglevel
to the ctx endpoints and service manager methods.
Tyler Goodlet