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Move maybe-raise-error-msg logic into context 

A context method handling all this logic makes the most sense since it
contains all the state related to whether the error should be raised in
a nursery scope or is expected to be raised by a consumer task which
reads and processes the msg directly (via a `Portal` API call). This
also makes it easy to always process remote errors even when there is no
(stream) overrun condition.
stricter_context_starting
Tyler Goodlet 2021-12-06 15:52:23 -05:00
parent 1f8e1cccbb
commit c9132de7dc
2 changed files with 76 additions and 79 deletions
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107
tractor/_actor.py
View File

@ -650,81 +650,56 @@ class Actor:
return return
send_chan = ctx._send_chan send_chan = ctx._send_chan
assert send_chan
error = msg.get('error') log.runtime(f"Delivering {msg} from {chan.uid} to caller {cid}")
if error:
# If this is an error message from a context opened by
# ``Portal.open_context()`` we want to interrupt any ongoing
# (child) tasks within that context to be notified of the remote
# error relayed here.
#
# The reason we may want to raise the remote error immediately
# is that there is no guarantee the associated local task(s)
# will attempt to read from any locally opened stream any time
# soon.
#
# NOTE: this only applies when
# ``Portal.open_context()`` has been called since it is assumed
# (currently) that other portal APIs (``Portal.run()``,
# ``.run_in_actor()``) do their own error checking at the point
# of the call and result processing.
log.warning(f'Remote context for {chan.uid}:{cid} errored {msg}')
ctx._maybe_error_from_remote_msg(msg)
# XXX: we do **not** maintain backpressure and instead
# opt to relay stream overrun errors to the sender.
try: try:
log.runtime(f"Delivering {msg} from {chan.uid} to caller {cid}") send_chan.send_nowait(msg)
# if an error is deteced we should always
# expect it to be raised by any context (stream)
# consumer task
await ctx._maybe_raise_from_remote_msg(msg)
# XXX: we do **not** maintain backpressure and instead except trio.WouldBlock:
# opt to relay stream overrun errors to the sender. # XXX: always push an error even if the local
try: # receiver is in overrun state.
send_chan.send_nowait(msg) await ctx._maybe_raise_from_remote_msg(msg)
except trio.WouldBlock:
# XXX: do we need this? uid = chan.uid
# if we're trying to push an error but we're in lines = [
# an overrun state we'll just get stuck sending 'Task context stream was overrun',
# the error that was sent to us back to it's sender f'local task: {cid} @ {self.uid}',
# instead of it actually being raises in the target f'remote sender: {uid}',
# task.. ]
# if error: if not ctx._stream_opened:
# raise unpack_error(msg, chan) from None lines.insert(
1,
f'\n*** No stream open on `{self.uid[0]}` side! ***\n'
)
text = '\n'.join(lines)
uid = chan.uid if ctx._backpressure:
lines = [
'Task context stream was overrun',
f'local task: {cid} @ {self.uid}',
f'remote sender: {chan.uid}',
]
if not ctx._stream_opened:
lines.insert(
1,
f'\n*** No stream open on `{self.uid[0]}` side! ***\n'
)
text = '\n'.join(lines)
log.warning(text) log.warning(text)
if ctx._backpressure: await send_chan.send(msg)
await send_chan.send(msg) else:
else: try:
raise StreamOverrun(text) from None
except StreamOverrun as err:
err_msg = pack_error(err)
err_msg['cid'] = cid
try: try:
raise StreamOverrun(text) from None # TODO: what is the right way to handle the case where the
except StreamOverrun as err: # local task has already sent a 'stop' / StopAsyncInteration
err_msg = pack_error(err) # to the other side but and possibly has closed the local
err_msg['cid'] = cid # feeder mem chan? Do we wait for some kind of ack or just
# let this fail silently and bubble up (currently)?
await chan.send(err_msg) await chan.send(err_msg)
except trio.BrokenResourceError:
except trio.BrokenResourceError: # XXX: local consumer has closed their side
# TODO: what is the right way to handle the case where the # so cancel the far end streaming task
# local task has already sent a 'stop' / StopAsyncInteration log.warning(f"{send_chan} consumer is already closed")
# to the other side but and possibly has closed the local
# feeder mem chan? Do we wait for some kind of ack or just
# let this fail silently and bubble up (currently)?
# XXX: local consumer has closed their side
# so cancel the far end streaming task
log.warning(f"{send_chan} consumer is already closed")
def get_context( def get_context(
self, self,

48
tractor/_streaming.py
View File

@ -364,33 +364,55 @@ class Context:
async def send_stop(self) -> None: async def send_stop(self) -> None:
await self.chan.send({'stop': True, 'cid': self.cid}) await self.chan.send({'stop': True, 'cid': self.cid})
def _maybe_error_from_remote_msg( async def _maybe_raise_from_remote_msg(
self, self,
msg: Dict[str, Any], msg: Dict[str, Any],
) -> None: ) -> None:
''' '''
Unpack and raise a msg error into the local scope (Maybe) unpack and raise a msg error into the local scope
nursery for this context. nursery for this context.
Acts as a form of "relay" for a remote error raised Acts as a form of "relay" for a remote error raised
in the corresponding remote callee task. in the corresponding remote callee task.
''' '''
self._error = unpack_error(msg, self.chan) error = msg.get('error')
if error:
# If this is an error message from a context opened by
# ``Portal.open_context()`` we want to interrupt any ongoing
# (child) tasks within that context to be notified of the remote
# error relayed here.
#
# The reason we may want to raise the remote error immediately
# is that there is no guarantee the associated local task(s)
# will attempt to read from any locally opened stream any time
# soon.
#
# NOTE: this only applies when
# ``Portal.open_context()`` has been called since it is assumed
# (currently) that other portal APIs (``Portal.run()``,
# ``.run_in_actor()``) do their own error checking at the point
# of the call and result processing.
log.error(
f'Remote context error for {self.chan.uid}:{self.cid}:\n'
f'{msg["error"]["tb_str"]}'
)
# await ctx._maybe_error_from_remote_msg(msg)
self._error = unpack_error(msg, self.chan)
# TODO: tempted to **not** do this by-reraising in a # TODO: tempted to **not** do this by-reraising in a
# nursery and instead cancel a surrounding scope, detect # nursery and instead cancel a surrounding scope, detect
# the cancellation, then lookup the error that was set? # the cancellation, then lookup the error that was set?
if self._scope_nursery: if self._scope_nursery:
async def raiser(): async def raiser():
raise self._error from None raise self._error from None
# from trio.testing import wait_all_tasks_blocked # from trio.testing import wait_all_tasks_blocked
# await wait_all_tasks_blocked() # await wait_all_tasks_blocked()
if not self._scope_nursery._closed: # type: ignore if not self._scope_nursery._closed: # type: ignore
self._scope_nursery.start_soon(raiser) self._scope_nursery.start_soon(raiser)
async def cancel(self) -> None: async def cancel(self) -> None:
''' '''