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from .log import logger
__all__ = (
'CancelledError', 'TimeoutError',
'FIRST_COMPLETED', 'FIRST_EXCEPTION', 'ALL_COMPLETED',
)
# Argument for default thread pool executor creation.
_MAX_WORKERS = 5
try:
import concurrent.futures
import concurrent.futures._base
except ImportError:
FIRST_COMPLETED = 'FIRST_COMPLETED'
FIRST_EXCEPTION = 'FIRST_EXCEPTION'
ALL_COMPLETED = 'ALL_COMPLETED'
class Future(object):
def __init__(self, callback, args):
try:
self._result = callback(*args)
self._exception = None
except Exception as err:
self._result = None
self._exception = err
self.callbacks = []
def cancelled(self):
return False
def done(self):
return True
def exception(self):
return self._exception
def result(self):
if self._exception is not None:
raise self._exception
else:
return self._result
def add_done_callback(self, callback):
callback(self)
class Error(Exception):
"""Base class for all future-related exceptions."""
pass
class CancelledError(Error):
"""The Future was cancelled."""
pass
class TimeoutError(Error):
"""The operation exceeded the given deadline."""
pass
class SynchronousExecutor:
"""
Synchronous executor: submit() blocks until it gets the result.
"""
def submit(self, callback, *args):
return Future(callback, args)
def shutdown(self, wait):
pass
def get_default_executor():
logger.error("concurrent.futures module is missing: "
"use a synchrounous executor as fallback!")
return SynchronousExecutor()
else:
FIRST_COMPLETED = concurrent.futures.FIRST_COMPLETED
FIRST_EXCEPTION = concurrent.futures.FIRST_EXCEPTION
ALL_COMPLETED = concurrent.futures.ALL_COMPLETED
Future = concurrent.futures.Future
Error = concurrent.futures._base.Error
CancelledError = concurrent.futures.CancelledError
TimeoutError = concurrent.futures.TimeoutError
def get_default_executor():
return concurrent.futures.ThreadPoolExecutor(_MAX_WORKERS)
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