/usr/lib/python2.7/dist-packages/Pyro4/futures.py is in python2-pyro4 4.63-1.
This file is owned by root:root, with mode 0o644.
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Support for Futures (asynchronously executed callables).
If you're using Python 3.2 or newer, also see
http://docs.python.org/3/library/concurrent.futures.html#future-objects
Pyro - Python Remote Objects. Copyright by Irmen de Jong (irmen@razorvine.net).
"""
import sys
import functools
import logging
import threading
import time
__all__ = ["Future", "FutureResult", "_ExceptionWrapper"]
log = logging.getLogger("Pyro4.futures")
class Future(object):
"""
Holds a callable that will be executed asynchronously and provide its
result value some time in the future.
This is a more general implementation than the AsyncRemoteMethod, which
only works with Pyro proxies (and provides a bit different syntax).
This class has a few extra features as well (delay, canceling).
"""
def __init__(self, somecallable):
self.callable = somecallable
self.chain = []
self.exceptionhandler = None
self.call_delay = 0
self.cancelled = False
self.completed = False
def __call__(self, *args, **kwargs):
"""
Start the future call with the provided arguments.
Control flow returns immediately, with a FutureResult object.
"""
if self.completed or not hasattr(self, "chain"):
raise RuntimeError("the future has already been evaluated")
if self.cancelled:
raise RuntimeError("the future has been cancelled")
chain = self.chain
del self.chain # make it impossible to add new calls to the chain once we started executing it
result = FutureResult() # notice that the call chain doesn't sit on the result object
thread = threading.Thread(target=self.__asynccall, args=(result, chain, args, kwargs))
thread.setDaemon(True)
thread.start()
return result
def __asynccall(self, asyncresult, chain, args, kwargs):
while self.call_delay > 0 and not self.cancelled:
delay = min(self.call_delay, 2)
time.sleep(delay)
self.call_delay -= delay
if self.cancelled:
self.completed = True
asyncresult.set_cancelled()
return
try:
self.completed = True
self.cancelled = False
value = self.callable(*args, **kwargs)
# now walk the callchain, passing on the previous value as first argument
for call, args, kwargs in chain:
call = functools.partial(call, value)
value = call(*args, **kwargs)
asyncresult.value = value
except Exception as x:
if self.exceptionhandler:
self.exceptionhandler(x)
asyncresult.value = _ExceptionWrapper(x)
def delay(self, seconds):
"""
Delay the evaluation of the future for the given number of seconds.
Return True if succesful otherwise False if the future has already been evaluated.
"""
if self.completed:
return False
self.call_delay = seconds
return True
def cancel(self):
"""
Cancels the execution of the future altogether.
If the execution hasn't been started yet, the cancellation is succesful and returns True.
Otherwise, it failed and returns False.
"""
if self.completed:
return False
self.cancelled = True
return True
def then(self, call, *args, **kwargs):
"""
Add a callable to the call chain, to be invoked when the results become available.
The result of the current call will be used as the first argument for the next call.
Optional extra arguments can be provided in args and kwargs.
Returns self so you can easily chain then() calls.
"""
self.chain.append((call, args, kwargs))
return self
def iferror(self, exceptionhandler):
"""
Specify the exception handler to be invoked (with the exception object as only
argument) when calculating the result raises an exception.
If no exception handler is set, any exception raised in the async call will be silently ignored.
Returns self so you can easily chain other calls.
"""
self.exceptionhandler = exceptionhandler
return self
class FutureResult(object):
"""
The result object for asynchronous Pyro calls.
Unfortunatley it should be similar to the more general Future class but
it is still somewhat limited (no delay, no canceling).
"""
def __init__(self):
self.__ready = threading.Event()
self.callchain = []
self.valueLock = threading.Lock()
self.exceptionhandler = None
def wait(self, timeout=None):
"""
Wait for the result to become available, with optional timeout (in seconds).
Returns True if the result is ready, or False if it still isn't ready.
"""
result = self.__ready.wait(timeout)
if result is None:
# older pythons return None from wait()
return self.__ready.isSet()
return result
@property
def ready(self):
"""Boolean that contains the readiness of the async result"""
return self.__ready.isSet()
def get_value(self):
self.__ready.wait()
if isinstance(self.__value, _ExceptionWrapper):
self.__value.raiseIt()
else:
return self.__value
def set_value(self, value):
with self.valueLock:
self.__value = value
# walk the call chain if the result is not an exception, otherwise invoke the errorhandler (if any)
if isinstance(value, _ExceptionWrapper):
if self.exceptionhandler:
self.exceptionhandler(value.exception)
else:
for call, args, kwargs in self.callchain:
call = functools.partial(call, self.__value)
self.__value = call(*args, **kwargs)
if isinstance(self.__value, _ExceptionWrapper):
break
self.callchain = []
self.__ready.set()
value = property(get_value, set_value, None, "The result value of the call. Reading it will block if not available yet.")
def set_cancelled(self):
self.set_value(_ExceptionWrapper(RuntimeError("future has been cancelled")))
def then(self, call, *args, **kwargs):
"""
Add a callable to the call chain, to be invoked when the results become available.
The result of the current call will be used as the first argument for the next call.
Optional extra arguments can be provided in args and kwargs.
Returns self so you can easily chain then() calls.
"""
with self.valueLock:
if self.__ready.isSet():
# value is already known, we need to process it immediately (can't use the call chain anymore)
call = functools.partial(call, self.__value)
self.__value = call(*args, **kwargs)
else:
# add the call to the call chain, it will be processed later when the result arrives
self.callchain.append((call, args, kwargs))
return self
def iferror(self, exceptionhandler):
"""
Specify the exception handler to be invoked (with the exception object as only
argument) when asking for the result raises an exception.
If no exception handler is set, any exception result will be silently ignored (unless
you explicitly ask for the value). Returns self so you can easily chain other calls.
"""
self.exceptionhandler = exceptionhandler
return self
class _ExceptionWrapper(object):
"""Class that wraps a remote exception. If this is returned, Pyro will
re-throw the exception on the receiving side. Usually this is taken care of
by a special response message flag, but in the case of batched calls this
flag is useless and another mechanism was needed."""
def __init__(self, exception):
self.exception = exception
def raiseIt(self):
from Pyro4.util import fixIronPythonExceptionForPickle # XXX circular
if sys.platform == "cli":
fixIronPythonExceptionForPickle(self.exception, False)
raise self.exception
def __serialized_dict__(self):
"""serialized form as a dictionary"""
from Pyro4.util import SerializerBase # XXX circular
return {
"__class__": "Pyro4.futures._ExceptionWrapper",
"exception": SerializerBase.class_to_dict(self.exception)
}
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