Found exactly why trying this won't work when playing around with
opening workspaces in `modden` using a `Portal.open_context()` back to
the 'bigd' root actor: the RPC machinery only registers one entry in
`Actor._contexts` which will get overwritten by each task's side and
then experience race-based IPC msging errors (eg. rxing `{'started': _}`
on the callee side..). Instead make opening a ctx back to the self-actor
a runtime error describing it as an invalid op.
To match:
- add a new test `test_ctx_with_self_actor()` to the context semantics
suite.
- tried out adding a new `side: str` to the `Actor.get_context()` (and
callers) but ran into not being able to determine the value from in
`._push_result()` where it's needed to figure out which side to push
to.. So, just leaving the commented arg (passing) in the runtime core
for now in case we can come back to trying to make it work, tho i'm
thinking it's not the right hack anyway XD
Since apparently `str(KeyboardInterrupt()) == ''`? So instead add little
`<str> or repr(merr)` expressions throughout to avoid blank strings
rendering if various `repr()`/`.__str__()` outputs..
Changes the condition logic to be more strict and moves it to a private
`._is_self_cancelled() -> bool` predicate which can be used elsewhere
(instead of having almost similar duplicate checks all over the
place..) and allows taking in a specific `remote_error` just for
verification purposes (like for tests).
Main strictness distinctions are now:
- obvi that `.cancel_called` is set (this filters any
`Portal.cancel_actor()` or other out-of-band RPC),
- the received `ContextCancelled` **must** have its `.canceller` set to
this side's `Actor.uid` (indicating we are the requester).
- `.src_actor_uid` **must** be the same as the `.chan.uid` (so the error
must have originated from the opposite side's task.
- `ContextCancelled.canceller` should be already set to the `.chan.uid`
indicating we received the msg via the runtime calling
`._deliver_msg()` -> `_maybe_cancel_and_set_remote_error()` which
ensures the error is specifically destined for this ctx-task exactly
the same as how `Actor._cancel_task()` sets it from an input
`requesting_uid` arg.
In support of the above adjust some impl deats:
- add `Context._actor: Actor` which is set once in `mk_context()` to
avoid issues (particularly in testing) where `current_actor()` raises
after the root actor / runtime is already exited. Use `._actor.uid` in
both `.cancel_acked` (obvi) and '_maybe_cancel_and_set_remote_error()`
when deciding whether to call `._scope.cancel()`.
- always cast `.canceller` to `tuple` if not null.
- delegate `.cancel_acked` directly to new private predicate (obvi).
- always set `._canceller` from any `RemoteActorError.src_actor_uid` or
failing over to the `.chan.uid` when a non-remote error (tho that
shouldn't ever happen right?).
- more extensive doc-string for `.cancel()` detailing the new strictness
rules about whether an eventual `.cancel_acked` might be set.
Also tossed in even more logging format tweaks by adding a
`type_only: bool` to `.repr_outcome()` as desired for simpler output in
the `state: <outcome-repr-here>` and `.repr_rpc()` sections of the
`.__str__()`.
Spanning from the pub API, to instance `repr()` customization (for
logging/REPL content), to the impl details around the notion of a "final
outcome" and surrounding IPC msg draining mechanics during teardown.
A few API and field updates:
- new `.cancel_acked: bool` to replace what we were mostly using
`.cancelled_caught: bool` for but, for purposes of better mapping the
semantics of remote cancellation of parallel executing tasks; it's set
only when `.cancel_called` is set and a ctxc arrives with
a `.canceller` field set to the current actor uid indicating we
requested and received acknowledgement from the other side's task
that is cancelled gracefully.
- strongly document and delegate (and prolly eventually remove as a pub
attr) the `.cancelled_caught` property entirely to the underlying
`._scope: trio.CancelScope`; the `trio` semantics don't really map
well to the "parallel with IPC msging" case in the sense that for
us it breaks the concept of the ctx/scope closure having "caught"
something instead of having "received" a msg that the other side has
"acknowledged" (i.e. which for us is the completion of cancellation).
- new `.__repr__()`/`.__str__()` format that tries to tersely yet
comprehensively as possible display everything you need to know about
the 3 main layers of an SC-linked-IPC-context:
* ipc: the transport + runtime layers net-addressing and prot info.
* rpc: the specific linked caller-callee task signature details
including task and msg-stream instances.
* state: current execution and final outcome state of the task pair.
* a teensie extra `.repr_rpc` for a condensed rpc signature.
- new `.dst_maddr` to get a `libp2p` style "multi-address" (though right
now it's just showing the transport layers so maybe we should move to
to our `Channel`?)
- new public instance-var fields supporting more granular remote
cancellation/result/error state:
* `.maybe_error: Exception|None` for any final (remote) error/ctxc
which computes logic on the values of `._remote_error`/`._local_error`
to determine the "final error" (if any) on termination.
* `.outcome` to the final error or result (or `None` if un-terminated)
* `.repr_outcome()` for a console/logging friendly version of the
final result or error as needed for the `.__str__()`.
- new private interface bits to support all of ^:
* a new "no result yet" sentinel value, `Unresolved`, using a module
level class singleton that `._result` is set too (instead of
`id(self)`) to both determine if and present when no final result
from the callee has-yet-been/was delivered (ever).
=> really we should get rid of `.result()` and change it to
`.wait_for_result()` (or something)u
* `_final_result_is_set()` predicate to avoid waiting for an already
delivered result.
* `._maybe_raise()` proto-impl that we should use to replace all the
`if re:` blocks it can XD
* new `._stream: MsgStream|None` for when a stream is opened to aid
with the state repr mentioned above.
Tweaks to the termination drain loop `_drain_to_final_msg()`:
- obviously (obvi) use all the changes above when determining whether or
not a "final outcome" has arrived and thus breaking from the loop ;)
* like the `.outcome` `.maybe_error` and `._final_ctx_is_set()` in
the `while` pred expression.
- drop the `_recv_chan.receive_nowait()` + guard logic since it seems
with all the surrounding (and coming soon) changes to
`Portal.open_context()` using all the new API stuff (mentioned in
first bullet set above) we never hit the case of inf-block?
Oh right and obviously a ton of (hopefully improved) logging msg content
changes, commented code removal and detailed comment-docs strewn about!
Since we use basically the exact same set of logic in
`Portal.open_context()` when expecting the first `'started'` msg factor
and generalize `._streaming._raise_from_no_yield_msg()` into a new
`._exceptions._raise_from_no_key_in_msg()` (as per the lingering todo)
which obvi requires a more generalized / optional signature including
a caller specific `log` obj. Obvi call the new func from all the other
modules X)
As part of extremely detailed inter-peer-actor testing, add much more
granular `Context` cancellation state tracking via the following (new)
fields:
- `.canceller: tuple[str, str]` the uuid of the actor responsible for
the cancellation condition - always set by
`Context._maybe_cancel_and_set_remote_error()` and replaces
`._cancelled_remote` and `.cancel_called_remote`. If set, this value
should normally always match a value from some `ContextCancelled`
raised or caught by one side of the context.
- `._local_error` which is always set to the locally raised (and caller
or callee task's scope-internal) error which caused any
eventual cancellation/error condition and thus any closure of the
context's per-task-side-`trio.Nursery`.
- `.cancelled_caught: bool` is now always `True` whenever the local task
catches (or "silently absorbs") a `ContextCancelled` (a `ctxc`) that
indeed originated from one of the context's linked tasks or any other
context which raised its own `ctxc` in the current `.open_context()` scope.
=> whenever there is a case that no `ContextCancelled` was raised
**in** the `.open_context().__aexit__()` (eg. `ctx.result()` called
after a call `ctx.cancel()`), we still consider the context's as
having "caught a cancellation" since the `ctxc` was indeed silently
handled by the cancel requester; all other error cases are already
represented by mirroring the state of the `._scope: trio.CancelScope`
=> IOW there should be **no case** where an error is **not raised** in
the context's scope and `.cancelled_caught: bool == False`, i.e. no
case where `._scope.cancelled_caught == False and ._local_error is not
None`!
- always raise any `ctxc` from `.open_stream()` if `._cancel_called ==
True` - if the cancellation request has not already resulted in
a `._remote_error: ContextCancelled` we raise a `RuntimeError` to
indicate improper usage to the guilty side's task code.
- make `._maybe_raise_remote_err()` a sync func and don't raise
any `ctxc` which is matched against a `.canceller` determined to
be the current actor, aka a "self cancel", and always set the
`._local_error` to any such `ctxc`.
- `.side: str` taken from inside `.cancel()` and unused as of now since
it might be better re-written as a similar `.is_opener() -> bool`?
- drop unused `._started_received: bool`..
- TONS and TONS of detailed comments/docs to attempt to explain all the
possible cancellation/exit cases and how they should exhibit as either
silent closes or raises from the `Context` API!
Adjust the `._runtime._invoke()` code to match:
- use `ctx._maybe_raise_remote_err()` in `._invoke()`.
- adjust to new `.canceller` property.
- more type hints.
- better `log.cancel()` msging around self-cancels vs. peer-cancels.
- always set the `._local_error: BaseException` for the "callee" task
just like `Portal.open_context()` now will do B)
Prior we were raising any `Context._remote_error` directly and doing
(more or less) the same `ContextCancelled` "absorbing" logic (well
kinda) in block; instead delegate to the method
Well first off, turns out it's never used and generally speaking
doesn't seem to help much with "runtime hacking/debugging"; why would
we need to "fabricate" a msg when `.cancel()` is called to self-cancel?
Also (and since `._maybe_cancel_and_set_remote_error()` now takes an
`error: BaseException` as input and thus expects error-msg unpacking
prior to being called), we now manually set `Context._cancel_msg: dict`
just prior to any remote error assignment - so any case where we would
have fabbed a "cancel msg" near calling `.cancel()`, just do the manual
assign.
In this vein some other subtle changes:
- obviously don't set `._cancel_msg` in `.cancel()` since it's no longer
an input.
- generally do walrus-style `error := unpack_error()` before applying
and setting remote error-msg state.
- always raise any `._remote_error` in `.result()` instead of returning
the exception instance and check before AND after the underlying mem
chan read.
- add notes/todos around `raise self._remote_error from None` masking of
(runtime) errors in `._maybe_raise_remote_err()` and use it inside
`.result()` since we had the inverse duplicate logic there anyway..
Further, this adds and extends a ton of (internal) interface docs and
details comments around the `Context` API including many subtleties
pertaining to calling `._maybe_cancel_and_set_remote_error()`.
Previously we weren't raising a remote error if the local scope was
cancelled during a call to `Context.result()` which is problematic if
the caller WAS NOT the requester for said remote cancellation; in that
case we still want a `ContextCancelled` raised with the `.canceller:
str` set to the cancelling actor uid.
Further fix a naming bug where the (seemingly older) `._remote_err` was
being set to such an error instead of `._remote_error` XD
- `Context._cancel_called_remote` -> `._cancelled_remote` since "called"
implies the cancellation was "requested" when it could be due to
another error and the actor uid is the value - only set once the far
end task scope is terminated due to either error or cancel, which has
nothing to do with *what* caused the cancellation.
- `Actor._cancel_called_remote` -> `._cancel_called_by_remote` which
emphasizes that this variable is **only set** IFF some remote actor
**requested that** this actor's runtime be cancelled via
`Actor.cancel()`.
Tyler Goodlet