If we pack the nursery parent task's error into the `errors` table
directly in the handler, we don't need to specially handle packing that
same error into any exception group raised while handling sub-actor
cancellation; drops some ugly indentation ;)
Pretty sure this is the final touch to alleviate all our debug lock
headaches! Instead of trying to revert to the "last" handler (as `pdb`
does internally in the stdlib) we always just revert to the handler
`trio` registers during startup. Further this seems to allow cancelling
the root-side locking task if it's detected as stale IFF we only do this
when the root actor is in a "no more IPC peers" state.
Deatz:
- (always) set `._debug.Lock._trio_handler` as the `trio` version, not
some last used handler to make sure we're getting the ctrl-c handling
we want when not in debug mode.
- assign the trio handler in `open_root_actor()`
`._runtime._async_main()` to be sure it's applied in subactors as well
as the root.
- only do debug lock blocking and root-side-locking-task cancels when
a "no peers" condition is detected in the root actor: i.e. no IPC
channels are detected by the root meaning it's impossible any actor
has a sane lock-state ongoing for debug mode.
This is a lingering debugger locking race case we needed to handle:
- child crashes acquires TTY lock in root and attaches to `pdb`
- child IPC goes down such that all channels to the root are broken
/ non-functional.
- root is stuck thinking the child is still in debug even though it
can't be contacted and the child actor machinery hasn't been
cancelled by its parent.
- root get's stuck in deadlock with child since it won't send a cancel
request until the child is finished debugging, but the child can't
unlock the debugger bc IPC is down.
To avoid this scenario add debug lock blocking list via
`._debug.Lock._blocked: set[tuple]` which holds actor uids for any actor
that is detected by the root as having no transport channel connections
with said root (of which at least one should exist if this sub-actor at
some point acquired the debug lock). The root consequently checks this
list for any actor that tries to (re)acquire the lock and blocks with
a `ContextCancelled`. When a debug condition is tested in
`._runtime._invoke` the context's `._enter_debugger_on_cancel` which
is set to `False` if the actor is on the block list in which case the
post-mortem entry is skipped.
Further this adds a root-locking-task side cancel scope to
`Lock._root_local_task_cs_in_debug` which can be cancelled by the root
runtime when a stale lock is detected after all IPC channels for the
actor have been torn down. NOTE: right now we're NOT doing this since it
seems to cause test failures likely due because it may cause pre-mature
cancellation and maybe needs a bit more experimenting?
In the case of a callee-side context cancelling itself it can be handy
to let the caller-side task know (even if through logging) that the
cancel was due to some known reason. Make `.cancel()` accept such
a message on the callee side and have it included in the
`._runtime._invoke()` raised `ContextCancelled` emission.
Also add a `Context._trigger_debugger_on_cancel: bool` flag which can be
set to `False` to avoid the debugger post-mortem crash mode from
engaging on cross-context tasks which cancel themselves for a known
reason (as is needed for blocked tasks in the debug TTY-lock machinery).
Turns out the lifetime mgmt of separate nurseries per delegate manager
is tricky; a new nursery can't be naively allocated on cache-misses since
it may get closed by some early terminating task instead of by the "last
using" consumer task. In theory if we allocate using the same logic as
that used for the last-task-triggers-exit then this should work?
For now just go back to a single global nursery per `_Cache` which still
avoids use of the internal actor service nursery.
Instead of sticking all `trionics.maybe_open_context()` tasks inside the
actor's (root) service nursery, open a unique one per manager function
instance (id).
Further, accept a callable for the `key` such that a user can have
more flexible control on the caching logic and move the
`maybe_open_nursery()` helper out of the portal mod and into this
trionics "managers" module.
Instead of the logic branching create a table `._spawn._methods`
which is used to lookup the desired backend framework (in this case
still only one of `multiprocessing` or `trio`) and make the top level
`.new_proc()` do the lookup and any common logic. Use a `typing.Literal`
to define the lookup table's key set.
Repair and ignore a bunch of type-annot related stuff todo with `mypy`
updates and backend-specific process typing.
The common logic to both remove our custom SIGINT handler as well
as signal the actor global event that pdb is complete. Call this
whenever we exit a post mortem call and thus any time some rpc task
get's debugged inside `._actor._invoke()`.
Further, we have to manually print the REPL prompt on 3.9 for some wack
reason, so stick a version guard in the sigint handler for that..
When in an uncertain teardown state and in debug mode a context can be
popped from actor runtime before a child finished debugging (the case
when the parent is tearing down but the child hasn't closed/completed
its tty lock IPC exit phase) and the child sends the "stop" message to
unlock the debugger but it's ignored bc the parent has already dropped
the ctx. Instead we call `._debug.maybe_wait_for_deugger()` before these
context removals to avoid the root getting stuck thinking the lock was
never released.
Further, add special `Actor._cancel_task()` handling code inside
`_invoke()` which continues to execute the method despite the IPC
channel to the caller being broken and thus avoiding potential hangs due
to a target (child) actor task remaining alive.
Tyler Goodlet