679 lines
26 KiB
Python
679 lines
26 KiB
Python
"""
|
|
aiosched: Yet another Python async scheduler
|
|
|
|
Copyright (C) 2022 nocturn9x
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain a copy of the License at
|
|
|
|
https:www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|
|
"""
|
|
import signal
|
|
import itertools
|
|
from collections import deque
|
|
from functools import partial
|
|
from aiosched.task import Task, TaskState
|
|
from timeit import default_timer
|
|
from aiosched.internals.queue import TimeQueue
|
|
from aiosched.util.debugging import BaseDebugger
|
|
from typing import Callable, Any, Coroutine
|
|
from aiosched.errors import (
|
|
InternalError,
|
|
ResourceBusy,
|
|
Cancelled,
|
|
ResourceClosed,
|
|
ResourceBroken,
|
|
)
|
|
from aiosched.context import TaskContext
|
|
from selectors import DefaultSelector, BaseSelector, EVENT_READ, EVENT_WRITE
|
|
|
|
|
|
class FIFOKernel:
|
|
"""
|
|
An asynchronous event loop implementation with a FIFO
|
|
scheduling policy.
|
|
|
|
:param clock: The function used to keep track of time. Defaults to timeit.default_timer
|
|
:param debugger: A subclass of aiosched.util.BaseDebugger or None if no debugging output is desired
|
|
:type debugger: :class: aiosched.util.debugging.BaseDebugger, optional
|
|
:param selector: The selector to use for I/O multiplexing, defaults to selectors.DefaultSelector
|
|
:type selector: :class: selectors.DefaultSelector
|
|
"""
|
|
|
|
def __init__(
|
|
self,
|
|
clock: Callable[[], float] = default_timer,
|
|
debugger: BaseDebugger | None = None,
|
|
selector: BaseSelector = DefaultSelector(),
|
|
):
|
|
"""
|
|
Public constructor
|
|
"""
|
|
|
|
self.clock = clock
|
|
if debugger and not issubclass(type(debugger), BaseDebugger):
|
|
raise InternalError(
|
|
"The debugger must be a subclass of aiosched.util.debugging.BaseDebugger"
|
|
)
|
|
# The debugger object. If it is none we create a dummy object that immediately returns an empty
|
|
# lambda which in turn returns None every time we access any of its attributes to avoid lots of
|
|
# if self.debugger clauses
|
|
self.debugger = (
|
|
debugger
|
|
or type(
|
|
"DumbDebugger",
|
|
(object,),
|
|
{"__getattr__": lambda *_: lambda *_: None},
|
|
)()
|
|
)
|
|
# Abstraction layer over low-level OS
|
|
# primitives for asynchronous I/O
|
|
self.selector: BaseSelector = selector
|
|
# Tasks that are ready to run
|
|
self.run_ready: deque[Task] = deque()
|
|
# Tasks that are paused and waiting
|
|
# for some deadline to expire
|
|
self.paused: TimeQueue = TimeQueue(self.clock)
|
|
# Data that is to be sent back to coroutines
|
|
self.data: dict[Task, Any] = {}
|
|
# The currently running task
|
|
self.current_task: Task | None = None
|
|
# The loop's entry point
|
|
self.entry_point: Task | None = None
|
|
# Did we receive a Ctrl+C?
|
|
self._sigint_handled: bool = False
|
|
# Are we executing any task code?
|
|
self._running: bool = False
|
|
|
|
def __repr__(self):
|
|
"""
|
|
Returns repr(self)
|
|
"""
|
|
|
|
fields = {
|
|
"debugger",
|
|
"run_ready",
|
|
"selector",
|
|
"clock",
|
|
"data",
|
|
"paused",
|
|
"current_task",
|
|
}
|
|
data = ", ".join(
|
|
name + "=" + str(value)
|
|
for name, value in zip(fields, (getattr(self, field) for field in fields))
|
|
)
|
|
return f"{type(self).__name__}({data})"
|
|
|
|
def _sigint_handler(self, *_args):
|
|
"""
|
|
Handles SIGINT
|
|
|
|
:return:
|
|
"""
|
|
|
|
self._sigint_handled = True
|
|
|
|
def done(self) -> bool:
|
|
"""
|
|
Returns whether the loop has no more work
|
|
to do
|
|
"""
|
|
|
|
if self.current_task and not self.current_task.done():
|
|
# Current task isn't done yet!
|
|
return False
|
|
if any([self.paused, self.run_ready]):
|
|
# There's tasks sleeping and/or on the
|
|
# ready queue!
|
|
return False
|
|
if self.get_active_io_count():
|
|
# We don't just do any([self.paused, self.run_ready, self.selector.get_map()])
|
|
# because we don't want to just know if there's any resources we're waiting on,
|
|
# but if there's at least one non-terminated task that owns a resource we're
|
|
# waiting on. This avoids issues such as the event loop never exiting if the
|
|
# user forgets to close a socket, for example
|
|
return False
|
|
return True
|
|
|
|
def close(self, force: bool = False):
|
|
"""
|
|
Closes the event loop. If force equals False,
|
|
which is the default, raises an InternalError
|
|
exception. If force equals True, cancels all
|
|
tasks
|
|
"""
|
|
|
|
if not self.done() and not force:
|
|
self.current_task.throw(
|
|
InternalError("cannot shut down a running event loop")
|
|
)
|
|
for task in self.all():
|
|
self.cancel(task)
|
|
|
|
def all(self) -> Task:
|
|
"""
|
|
Yields all the tasks the event loop is keeping track of
|
|
"""
|
|
|
|
for task in itertools.chain(self.run_ready, self.paused):
|
|
task: Task
|
|
yield task
|
|
|
|
def shutdown(self):
|
|
"""
|
|
Shuts down the event loop
|
|
"""
|
|
|
|
for task in self.all():
|
|
self.io_release_task(task)
|
|
self.selector.close()
|
|
self.close()
|
|
|
|
def wait_io(self):
|
|
"""
|
|
Waits for I/O and schedules tasks when their
|
|
associated resource is ready to be used
|
|
"""
|
|
|
|
self._running = False
|
|
before_time = self.clock() # Used for the debugger
|
|
timeout = 0.0
|
|
if self.run_ready:
|
|
# If there is work to do immediately (tasks to run) we
|
|
# can't wait.
|
|
# TODO: This could cause I/O starvation in highly concurrent
|
|
# environments: maybe a more convoluted scheduling strategy
|
|
# where I/O timeouts can only be skipped n times before a
|
|
# mandatory x-second timeout occurs is needed? It should of
|
|
# course take deadlines into account so that timeouts are
|
|
# always delivered in a timely manner and tasks awake from
|
|
# sleeping at the right moment
|
|
timeout = 0.0
|
|
elif self.paused:
|
|
# If there are asleep tasks or deadlines, wait until the closest date
|
|
timeout = self.paused.get_closest_deadline() - self.clock()
|
|
self.debugger.before_io(timeout)
|
|
# Get sockets that are ready and schedule their tasks
|
|
for key, _ in self.selector.select(timeout):
|
|
key.data: dict[int, Task]
|
|
for task in key.data.values():
|
|
# We don't reschedule a task that wasn't
|
|
# blocking on I/O before: this way if a
|
|
# task waits on a socket and then goes to
|
|
# sleep, it won't be woken up early if the
|
|
# resource becomes available before its
|
|
# deadline expires
|
|
self.run_ready.append(task) # Resource ready? Schedule its task
|
|
self.debugger.after_io(self.clock() - before_time)
|
|
|
|
def awake_tasks(self):
|
|
"""
|
|
Reschedules paused tasks if their deadline
|
|
has elapsed
|
|
"""
|
|
|
|
self._running = False
|
|
while self.paused and self.paused.get_closest_deadline() <= self.clock():
|
|
# Reschedules tasks when their deadline has elapsed
|
|
task, _ = self.paused.get()
|
|
slept = self.clock() - task.paused_when
|
|
self.run_ready.append(task)
|
|
task.paused_when = 0
|
|
task.next_deadline = 0
|
|
self.debugger.after_sleep(task, slept)
|
|
|
|
def reschedule_running(self):
|
|
"""
|
|
Reschedules the currently running task
|
|
"""
|
|
|
|
self.run_ready.append(self.current_task)
|
|
|
|
def schedule(self, task: Task):
|
|
"""
|
|
Schedules a task that was previously
|
|
suspended
|
|
"""
|
|
|
|
self.run_ready.append(task)
|
|
self.reschedule_running()
|
|
|
|
def suspend(self):
|
|
"""
|
|
Suspends execution of the current task. This is basically
|
|
a do-nothing method, since it will not reschedule the task
|
|
before returning. The task will stay suspended as long as
|
|
something else outside the loop reschedules it (possibly
|
|
forever)
|
|
"""
|
|
|
|
self.current_task.state = TaskState.PAUSED
|
|
|
|
def run_task_step(self):
|
|
"""
|
|
Runs a single step for the current task.
|
|
A step ends when the task awaits any of
|
|
our primitives or async methods.
|
|
|
|
Note that this method does NOT catch any
|
|
errors arising from tasks, nor does it take
|
|
StopIteration or Cancelled exceptions into
|
|
account
|
|
"""
|
|
|
|
# Sets the currently running task
|
|
self.current_task = self.run_ready.popleft()
|
|
while self.current_task.done():
|
|
# We make sure not to schedule
|
|
# any terminated tasks. Might want
|
|
# to eventually get rid of this code,
|
|
# but for now it does the job
|
|
if not self.run_ready:
|
|
# We'll let run() handle the I/O
|
|
# or the shutdown if necessary, as
|
|
# there are no more runnable tasks
|
|
return
|
|
self.current_task = self.run_ready.popleft()
|
|
# We nullify the exception object just in case the
|
|
# entry point raised and caught an error so that
|
|
# self.start() doesn't raise it again at the end
|
|
self.current_task.exc = None
|
|
self.debugger.before_task_step(self.current_task)
|
|
self._running = True
|
|
# Some debugging and internal chatter here
|
|
self.current_task.state = TaskState.RUN
|
|
self.current_task.steps += 1
|
|
if self._sigint_handled:
|
|
self._sigint_handled = False
|
|
self.current_task.throw(KeyboardInterrupt())
|
|
elif self.current_task.pending_cancellation:
|
|
# We perform the deferred cancellation
|
|
# if it was previously scheduled
|
|
self.cancel(self.current_task)
|
|
else:
|
|
# Run a single step with the calculation (i.e. until a yield
|
|
# somewhere)
|
|
method, args, kwargs = self.current_task.run(
|
|
self.data.pop(self.current_task, None)
|
|
)
|
|
if not hasattr(self, method) or not callable(getattr(self, method)):
|
|
# This if block is meant to be triggered by other async
|
|
# libraries, which most likely have different method names and behaviors
|
|
# compared to us. If you get this exception, and you're 100% sure you're
|
|
# not mixing async primitives from other libraries, then it's a bug!
|
|
self.current_task.throw(
|
|
InternalError(
|
|
"Uh oh! Something bad just happened: did you try to mix primitives from other async libraries?"
|
|
)
|
|
)
|
|
# Sneaky method call, thanks to David Beazley for this ;)
|
|
getattr(self, method)(*args, **kwargs)
|
|
self.debugger.after_task_step(self.current_task)
|
|
|
|
def run(self):
|
|
"""
|
|
The event loop's runner function. This method drives
|
|
execution for the entire framework and orchestrates I/O,
|
|
events, sleeping, cancellations and deadlines, but the
|
|
actual functionality for all of that is implemented in
|
|
object wrappers. This keeps the size of this module to
|
|
a minimum while allowing anyone to replace it with their
|
|
own, as long as the system calls required by higher-level
|
|
object wrappers are implemented. If you want to add features
|
|
to the library, don't add them here, but take inspiration
|
|
from the current API (i.e. not depending on any implementation
|
|
detail from the loop aside from system calls)
|
|
"""
|
|
|
|
while True:
|
|
if self.done():
|
|
# If we're done, which means there are
|
|
# both no paused tasks and no running tasks, we
|
|
# simply tear us down and return to self.start
|
|
self.shutdown()
|
|
break
|
|
elif self._sigint_handled:
|
|
# We got Ctrl+C-ed while not running a task! Pick a
|
|
# random task and blow it up with a KeyboardInterrupt
|
|
# exception: our existing error handling machinery will
|
|
# deal with it accordingly
|
|
task: Task | None = None
|
|
if self.selector.get_map():
|
|
# Pretty convoluted, huh? Sorry, but I wanted this on one line ;)
|
|
task = next(iter(next(iter(self.selector.get_map().values())).data.values()))
|
|
elif self.paused:
|
|
# TODO
|
|
task = None
|
|
self.run_ready.append(task)
|
|
self.handle_errors(self.run_task_step)
|
|
elif not self.run_ready:
|
|
# If there are no actively running tasks, we start by
|
|
# checking for I/O. This method will wait for I/O until
|
|
# the closest deadline to avoid starving sleeping tasks
|
|
# or missing deadlines
|
|
if self.selector.get_map():
|
|
self.wait_io()
|
|
if self.paused:
|
|
# Next we check for deadlines
|
|
self.awake_tasks()
|
|
else:
|
|
# Otherwise, while there are tasks ready to run, we run them!
|
|
self.handle_errors(self.run_task_step)
|
|
|
|
def start(
|
|
self, func: Callable[..., Coroutine[Any, Any, Any]], *args, **kwargs
|
|
) -> Any:
|
|
"""
|
|
Starts the event loop from a synchronous context
|
|
"""
|
|
|
|
signal.signal(signal.SIGINT, self._sigint_handler)
|
|
self.entry_point = Task(func.__name__ or str(func), func(*args, **kwargs))
|
|
self.run_ready.append(self.entry_point)
|
|
self.debugger.on_start()
|
|
try:
|
|
self.run()
|
|
finally:
|
|
self.debugger.on_exit()
|
|
if (
|
|
self.entry_point.exc
|
|
and self.entry_point.context is None
|
|
and self.entry_point.propagate
|
|
):
|
|
# Contexts already manage exceptions for us,
|
|
# no need to raise it manually. If a context
|
|
# is not used, *then* we can raise the error
|
|
raise self.entry_point.exc
|
|
return self.entry_point.result
|
|
|
|
def io_release(self, resource):
|
|
"""
|
|
Releases the given resource from our
|
|
selector
|
|
:param resource: The resource to be released
|
|
"""
|
|
|
|
if resource in self.selector.get_map():
|
|
self.selector.unregister(resource)
|
|
self.debugger.on_io_unschedule(resource)
|
|
if resource is self.current_task.last_io[1]:
|
|
self.current_task.last_io = ()
|
|
self.reschedule_running()
|
|
|
|
def io_release_task(self, task: Task):
|
|
"""
|
|
Calls self.io_release in a loop
|
|
for each I/O resource the given task owns
|
|
"""
|
|
|
|
for key in filter(
|
|
lambda k: task in k.data.values(), dict(self.selector.get_map()).values()
|
|
):
|
|
self.notify_closing(key.fileobj, broken=True)
|
|
self.selector.unregister(key.fileobj)
|
|
task.last_io = ()
|
|
|
|
def get_active_io_count(self) -> int:
|
|
"""
|
|
Returns the number of streams that are currently
|
|
being used by any active task
|
|
"""
|
|
|
|
result = 0
|
|
for key in (self.selector.get_map() or {}).values():
|
|
key.data: dict[int, Task]
|
|
for task in key.data.values():
|
|
if task.done():
|
|
continue
|
|
result += 1
|
|
return result
|
|
|
|
def notify_closing(self, stream, broken: bool = False):
|
|
"""
|
|
Notifies paused tasks that a stream
|
|
is about to be closed. The stream
|
|
itself is not touched and must be
|
|
closed by the caller
|
|
"""
|
|
|
|
if not broken:
|
|
exc = ResourceClosed("stream has been closed")
|
|
else:
|
|
exc = ResourceBroken("stream might be corrupted")
|
|
for k in filter(
|
|
lambda o: o.fileobj == stream,
|
|
dict(self.selector.get_map()).values(),
|
|
):
|
|
for task in k.data.values():
|
|
if task is not self.current_task:
|
|
# We don't want to raise an error inside
|
|
# the task that's trying to close the stream!
|
|
self.handle_errors(partial(k.data.throw, exc), k.data)
|
|
self.reschedule_running()
|
|
|
|
def cancel(self, task: Task):
|
|
"""
|
|
Attempts to cancel the given task or
|
|
schedules cancellation for later if
|
|
it fails
|
|
"""
|
|
|
|
self.handle_errors(partial(task.throw, Cancelled(task)), task)
|
|
if task.state != TaskState.CANCELLED:
|
|
task.pending_cancellation = True
|
|
self.io_release_task(task)
|
|
self.paused.discard(task)
|
|
self.reschedule_running()
|
|
|
|
def handle_errors(self, func: Callable, task: Task | None = None):
|
|
"""
|
|
Convenience method for handling various exceptions
|
|
from tasks
|
|
"""
|
|
|
|
try:
|
|
func()
|
|
except StopIteration as ret:
|
|
# We re-define it because we call run_task_step
|
|
# with this method and that changes the current
|
|
# task
|
|
task = task or self.current_task
|
|
# At the end of the day, coroutines are generator functions with
|
|
# some tricky behaviors, and this is one of them. When a coroutine
|
|
# hits a return statement (either explicit or implicit), it raises
|
|
# a StopIteration exception, which has an attribute named value that
|
|
# represents the return value of the coroutine, if it has one. Of course
|
|
# this exception is not an error, and we should happily keep going after it:
|
|
# most of this code below is just useful for internal/debugging purposes
|
|
task.state = TaskState.FINISHED
|
|
task.result = ret.value
|
|
self.wait(task)
|
|
except Cancelled:
|
|
# When a task needs to be cancelled, aiosched tries to do it gracefully
|
|
# first: if the task is paused in either I/O or sleeping, that's perfect.
|
|
# But we also need to cancel a task if it was not sleeping or waiting on
|
|
# any I/O because it could never do so (therefore blocking everything
|
|
# forever). So, when cancellation can't be done right away, we schedule
|
|
# it for the next execution step of the task. aiosched will also make sure
|
|
# to re-raise cancellations at every checkpoint until the task lets the
|
|
# exception propagate into us, because we *really* want the task to be
|
|
# cancelled
|
|
task = task or self.current_task
|
|
task.state = TaskState.CANCELLED
|
|
task.pending_cancellation = False
|
|
self.debugger.after_cancel(task)
|
|
self.wait(task)
|
|
except Exception as err:
|
|
# Any other exception is caught here
|
|
task = task or self.current_task
|
|
task.exc = err
|
|
task.state = TaskState.CRASHED
|
|
self.debugger.on_exception_raised(task, err)
|
|
self.wait(task)
|
|
|
|
def sleep(self, seconds: int | float):
|
|
"""
|
|
Puts the current task to sleep for a given amount of seconds
|
|
"""
|
|
|
|
if seconds:
|
|
self.debugger.before_sleep(self.current_task, seconds)
|
|
self.paused.put(self.current_task, seconds)
|
|
else:
|
|
# When we're called with a timeout of 0, this method acts as a checkpoint
|
|
# that allows aiosched to kick in and to its job without pausing the task's
|
|
# execution for too long. It is recommended to put a couple of checkpoints
|
|
# like these in your code if you see degraded concurrent performance in parts
|
|
# of your code that block the loop
|
|
self.reschedule_running()
|
|
|
|
def wait(self, task: Task):
|
|
"""
|
|
Makes the current task wait for completion of the given one
|
|
by only rescheduling it once the given task has finished
|
|
executing
|
|
"""
|
|
|
|
if task.done():
|
|
self.paused.discard(task)
|
|
self.io_release_task(task)
|
|
self.run_ready.extend(task.joiners)
|
|
|
|
def join(self, task: Task):
|
|
"""
|
|
Tells the event loop that the current task
|
|
wants to wait on the given one, but without
|
|
actually waiting for its completion
|
|
"""
|
|
|
|
task.joiners.add(self.current_task)
|
|
self.reschedule_running()
|
|
|
|
def spawn(self, func: Callable[..., Coroutine[Any, Any, Any]], *args, **kwargs):
|
|
"""
|
|
Spawns a task from a coroutine function. All positional and keyword arguments
|
|
besides the coroutine function itself are passed to the newly created coroutine
|
|
"""
|
|
|
|
task = Task(func.__name__ or repr(func), func(*args, **kwargs))
|
|
self.data[self.current_task] = task
|
|
self.run_ready.append(task)
|
|
self.reschedule_running()
|
|
self.debugger.on_task_spawn(task)
|
|
|
|
def set_context(self, ctx: TaskContext):
|
|
"""
|
|
Sets the current task context. This is
|
|
implemented as simply wrapping the current
|
|
task inside the context and replacing the
|
|
Task object with the TaskContext one. This
|
|
may also wrap another task context into a
|
|
new one, but the loop doesn't need to care
|
|
about that: the API is designed exactly for
|
|
this
|
|
"""
|
|
|
|
ctx.entry_point = self.current_task
|
|
ctx.tasks.append(ctx.entry_point)
|
|
self.current_task.context = ctx
|
|
self.current_task = ctx
|
|
self.debugger.on_context_creation(ctx)
|
|
self.reschedule_running()
|
|
|
|
def close_context(self, ctx: TaskContext):
|
|
"""
|
|
Closes the given context
|
|
"""
|
|
|
|
self.debugger.on_context_exit(ctx)
|
|
task = ctx.entry_point
|
|
task.context = None
|
|
self.current_task = task
|
|
self.reschedule_running()
|
|
|
|
def get_current_task(self):
|
|
"""
|
|
Returns the current task to an asynchronous
|
|
caller
|
|
"""
|
|
|
|
self.data[self.current_task] = self.current_task
|
|
self.reschedule_running()
|
|
|
|
def perform_io(self, resource, evt_type: int):
|
|
"""
|
|
Registers the given resource inside our selector to perform I/O multiplexing
|
|
|
|
:param resource: The resource on which a read or write operation
|
|
has to be performed
|
|
:param evt_type: The type of event to perform on the given
|
|
socket, either selectors.EVENT_READ or selectors.EVENT_WRITE
|
|
:type evt_type: int
|
|
"""
|
|
|
|
self.current_task.state = TaskState.IO
|
|
if self.current_task.last_io:
|
|
# Since most of the time tasks will perform multiple
|
|
# I/O operations on a given resource, unregistering them
|
|
# every time isn't a sensible approach. A quick and
|
|
# easy optimization to address this problem is to
|
|
# store the last I/O operation that the task performed,
|
|
# together with the resource itself, inside the task
|
|
# object. If the task then tries to perform the same
|
|
# operation on the same resource again, this method then
|
|
# returns immediately as the resource is already being watched
|
|
# by the selector. If the resource is the same, but the
|
|
# event type has changed, then we modify the resource's
|
|
# associated event. Only if the resource is different from
|
|
# the last one used then this method will register a new
|
|
# one
|
|
if self.current_task.last_io == (evt_type, resource):
|
|
# Selector is already listening for that event on
|
|
# this resource
|
|
return
|
|
elif self.current_task.last_io[1] == resource:
|
|
# If the event to listen for has changed we just modify it
|
|
self.selector.modify(resource, evt_type, {evt_type: self.current_task})
|
|
self.current_task.last_io = (evt_type, resource)
|
|
self.debugger.on_io_schedule(resource, evt_type)
|
|
elif not self.current_task.last_io or self.current_task.last_io[1] != resource:
|
|
# The task has either registered a new resource or is doing
|
|
# I/O for the first time
|
|
self.current_task.last_io = evt_type, resource
|
|
try:
|
|
self.selector.register(resource, evt_type, {evt_type: self.current_task})
|
|
self.debugger.on_io_schedule(resource, evt_type)
|
|
except KeyError:
|
|
# The stream is already being used
|
|
key = self.selector.get_key(resource)
|
|
if key.data[key.events] == self.current_task:
|
|
# If the task that registered the stream
|
|
# changed their mind on what they want
|
|
# to do with it, who are we to deny their
|
|
# request?
|
|
self.selector.modify(resource, key.events | evt_type, {EVENT_READ: self.current_task,
|
|
EVENT_WRITE: self.current_task})
|
|
self.debugger.on_io_schedule(resource, evt_type)
|
|
elif key.events != evt_type:
|
|
# We also modify the event in
|
|
# our selector so that one task can read
|
|
# off a given stream while another one is
|
|
# writing to it
|
|
self.selector.modify(resource, key.events | evt_type, {evt_type: self.current_task,
|
|
key.events: list(key.data.values())[0]})
|
|
else:
|
|
# One task reading and one writing on the same
|
|
# resource is fine (think producer-consumer),
|
|
# but having two tasks reading/writing at the
|
|
# same time can't lead to anything good, better
|
|
# disallow it
|
|
self.current_task.throw(ResourceBusy(f"The resource is being read from/written by another task"))
|