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Enso-Bot/venv/Lib/site-packages/asgiref/current_thread_executor.py

87 lines
2.9 KiB
Python

import queue
import threading
import time
from concurrent.futures import Executor, Future
class _WorkItem(object):
"""
Represents an item needing to be run in the executor.
Copied from ThreadPoolExecutor (but it's private, so we're not going to rely on importing it)
"""
def __init__(self, future, fn, args, kwargs):
self.future = future
self.fn = fn
self.args = args
self.kwargs = kwargs
def run(self):
if not self.future.set_running_or_notify_cancel():
return
try:
result = self.fn(*self.args, **self.kwargs)
except BaseException as exc:
self.future.set_exception(exc)
# Break a reference cycle with the exception 'exc'
self = None
else:
self.future.set_result(result)
class CurrentThreadExecutor(Executor):
"""
An Executor that actually runs code in the thread it is instantiated in.
Passed to other threads running async code, so they can run sync code in
the thread they came from.
"""
def __init__(self):
self._work_thread = threading.current_thread()
self._work_queue = queue.Queue()
self._broken = False
def run_until_future(self, future):
"""
Runs the code in the work queue until a result is available from the future.
Should be run from the thread the executor is initialised in.
"""
# Check we're in the right thread
if threading.current_thread() != self._work_thread:
raise RuntimeError(
"You cannot run CurrentThreadExecutor from a different thread"
)
# Keep getting work items and checking the future
try:
while True:
# Get a work item and run it
try:
work_item = self._work_queue.get(block=False)
except queue.Empty:
# See if the future is done (we only exit if the work queue is empty)
if future.done():
return
# Prevent hot-looping on nothing
time.sleep(0.001)
else:
work_item.run()
del work_item
finally:
self._broken = True
def submit(self, fn, *args, **kwargs):
# Check they're not submitting from the same thread
if threading.current_thread() == self._work_thread:
raise RuntimeError(
"You cannot submit onto CurrentThreadExecutor from its own thread"
)
# Check they're not too late or the executor errored
if self._broken:
raise RuntimeError("CurrentThreadExecutor already quit or is broken")
# Add to work queue
f = Future()
work_item = _WorkItem(f, fn, args, kwargs)
self._work_queue.put(work_item)
# Return the future
return f