Finally this makes a cancelled root actor nursery not clobber child
tasks which request and lock the root's tty for the debugger repl.
Using an edge triggered event which is set after all fifo-lock-queued
tasks are complete, we can be sure that no lingering child tasks are
going to get interrupted during pdb use and tty lock acquisition.
Further, even if new tasks do queue up to get the lock, the root will
incrementally send cancel msgs to each sub-actor only once the tty is
not locked by a (set of) child request task(s). Add shielding around all
the critical sections where the child attempts to allocate the lock from
the root such that it won't be disrupted from cancel messages from the
root after the acquire lock transaction has started.
This resolves and completes #69 allowing all RPC invocation APIs to pass
function references directly instead of explicit `str` names for the
target namespace and function (this is still done implicitly
underneath). This brings us closer to `trio`'s task running API as well
as acknowledges that any inter-host RPC system (and API) will likely
need to be implemented on top of local RPC primitives anyway. Even if
this ends up **not** being true we can always go to "function stubs" as
part of our IAC protocol or, add a new method to do explicit namespace
calls: `.run_from_module()` or whatever everyone votes on.
Resolves#69
Further, this commit drops `Actor.statespace` from the entire system
since a user can easily get this same functionality using module
level variables. Fix docs to match all these changes (luckily mostly
already done due to example scripts referencing).
It's not like any of this code is really being used anyway since we
aren't indefinitely blocking for cancelled subactors to terminate (yet).
Drop the `do_hard_kill()` bit for now and just rely on the underlying
process api. Oh, and mark the nursery as cancelled asap.
Allow entering and attaching to a `pdb` instance in a child process.
The current hackery is to have the child make an rpc to the parent and
ask it to hijack stdin, once complete the child enters a `pdb` blocking
method. The parent then relays all stdin input to the child thus
controlling the "remote" debugger.
A few things were added to accomplish this:
- tracking the mapping of subactors to their parent nurseries
- in the root actor, cancelling all nurseries under the root `trio` task
on cancellation (i.e. `Actor.cancel()`)
- pass a "runtime vars" map down the actor tree for propagating global state
This is an edit to factor out changes needed for the `asyncio` in guest mode
integration (which currently isn't tested well) so that later more pertinent
changes (which are tested well) can be rebased off of this branch and
merged into mainline sooner. The *infect_asyncio* branch will need to be
rebased onto this branch as well before merge to mainline.
This is an initial solution for #120.
Allow spawning `asyncio` based actors which run `trio` in guest
mode. This enables spawning `tractor` actors on top of the `asyncio`
event loop whilst still leveraging the SC focused internal actor
supervision machinery. Add a `tractor.to_syncio.run()` api to allow
spawning tasks on the `asyncio` loop from an embedded (remote) `trio`
task and return or stream results all the way back through the `tractor`
IPC system using a very similar api to portals.
One outstanding problem is getting SC around calls to
`asyncio.create_task()`. Currently a task that crashes isn't able to
easily relay the error to the embedded `trio` task without us fully
enforcing the portals based message protocol (which seems superfluous
given the error ref is in process). Further experiments using `anyio`
task groups may alleviate this.
The logic in the `ActorNursery` block is critical to cancellation
semantics and in particular, understanding how supervisor strategies are
invoked. Stick in a bunch of explanatory comments to clear up these
details and also prepare to introduce more supervisor strats besides
the current one-cancels-all approach.
Thanks to @salotz for pointing out that the first example in the docs
was broken. Though it's somewhat embarrassing this might also explain
the problem in #79 and certain issues in #59...
The solution here is to import the target RPC module using the its
unique basename and absolute filepath in the sub-actor that requires it.
Special handling for `__main__` and `__mp_main__` is needed since the
spawned subprocess will have no knowledge about these parent-
-state-specific module variables. Solution: map the modules name to the
respective module file basename in the child process since the module
variables will of course have different values in children.
This took a ton of tinkering and a rework of the actor nursery tear down
logic. The main changes include:
- each subprocess is now spawned from inside a trio task
from one of two containing nurseries created in the body of
`tractor.open_nursery()`: one for `run_in_actor()` processes and one for
`start_actor()` "daemons". This is to address the need for
`trio-run-in_process.open_in_process()` opening a nursery which must
be closed from the same task that opened it. Using this same approach
for `multiprocessing` seems to work well. The nurseries are waited in
order (rip actors then daemon actors) during tear down which allows
for avoiding the recursive re-entry of `ActorNursery.wait()` handled
prior.
- pull out all the nested functions / closures that were in
`ActorNursery.wait()` and move into the `_spawn` module such that
that process shutdown logic takes place in each containing task's
code path. This allows for vastly simplifying `.wait()` to just contain an
event trigger which initiates process waiting / result collection.
Likely `.wait()` should just be removed since it can no longer be used
to synchronously wait on the actor nursery.
- drop `ActorNursery.__aenter__()` / `.__atexit__()` and move this
"supervisor" tear down logic into the closing block of `open_nursery()`.
This not only cleans makes the code more comprehensible it also
makes our nursery implementation look more like the one in `trio`.
Resolves#93
Get a few more things working:
- fail reliably when remote module loading goes awry
- do a real hacky job of module loading using `sys.path` stuffsies
- we're still totally borked when trying to spin up and quickly cancel
a bunch of subactors...
It's a small move forward I guess.
If a nursery fails to cancel (some sub-actors presumably) then hard kill
the whole process tree to avoid hangs during a catastrophic failure.
This logic may get factored out (and changed) as we introduce custom
supervisor strategies.
At the expense of a bit more complexity in `ActorNursery.wait()`
(which I commented the heck out of fwiw) this adds far superior and
correct cancellation semantics for when a nursery is cancelled due
to (remote) errors in subactors.
This includes:
- `wait()` will now raise a `trio.MultiError` if multiple subactors
error with the same semantics as in `trio`.
- in `wait()` portals which are paired with `run_in_actor()`
spawned subactors (versus `start_actor()`) are waited on separately
and if the nursery **hasn't** been cancelled but there are errors
those are raised immediately before waiting on `start_actor()`
subactors which will block indefinitely if they haven't been
explicitly cancelled.
- if `wait()` does raise when the nursery hasn't yet been cancelled
it's expected that it will be called again depending on the actor
supervision strategy (i.e. right now we operate with a one-cancels-all
strategy, the same as `trio`, so `ActorNursery.__aexit__() calls
`cancel()` if any error is raised by `wait()`).
Oh and I added `is_main_process()` helper; can't remember why..
Tyler Goodlet
Tyler Goodlet