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#!/usr/bin/env python
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# encoding: utf-8
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"""Things directly related to all of twisted."""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2008-2009 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import os, sys
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import threading, Queue
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import twisted
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from twisted.internet import defer, reactor
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from twisted.python import log, failure
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from IPython.kernel.error import FileTimeoutError
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#-----------------------------------------------------------------------------
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# Classes related to twisted and threads
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#-----------------------------------------------------------------------------
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class ReactorInThread(threading.Thread):
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"""Run the twisted reactor in a different thread.
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For the process to be able to exit cleanly, do the following:
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rit = ReactorInThread()
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rit.setDaemon(True)
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rit.start()
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"""
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def run(self):
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"""Run the twisted reactor in a thread.
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This runs the reactor with installSignalHandlers=0, which prevents
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twisted from installing any of its own signal handlers. This needs to
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be disabled because signal.signal can't be called in a thread. The
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only problem with this is that SIGCHLD events won't be detected so
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spawnProcess won't detect that its processes have been killed by
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an external factor.
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"""
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reactor.run(installSignalHandlers=0)
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# self.join()
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def stop(self):
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# I don't think this does anything useful.
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blockingCallFromThread(reactor.stop)
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self.join()
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if(twisted.version.major >= 8):
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import twisted.internet.threads
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def blockingCallFromThread(f, *a, **kw):
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"""
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Run a function in the reactor from a thread, and wait for the result
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synchronously, i.e. until the callback chain returned by the function get a
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result.
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Delegates to twisted.internet.threads.blockingCallFromThread(reactor, f, *a, **kw),
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passing twisted.internet.reactor for the first argument.
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@param f: the callable to run in the reactor thread
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@type f: any callable.
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@param a: the arguments to pass to C{f}.
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@param kw: the keyword arguments to pass to C{f}.
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@return: the result of the callback chain.
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@raise: any error raised during the callback chain.
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"""
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return twisted.internet.threads.blockingCallFromThread(reactor, f, *a, **kw)
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else:
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def blockingCallFromThread(f, *a, **kw):
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"""
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Run a function in the reactor from a thread, and wait for the result
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synchronously, i.e. until the callback chain returned by the function get a
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result.
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@param f: the callable to run in the reactor thread
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@type f: any callable.
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@param a: the arguments to pass to C{f}.
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@param kw: the keyword arguments to pass to C{f}.
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@return: the result of the callback chain.
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@raise: any error raised during the callback chain.
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"""
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from twisted.internet import reactor
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queue = Queue.Queue()
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def _callFromThread():
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result = defer.maybeDeferred(f, *a, **kw)
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result.addBoth(queue.put)
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reactor.callFromThread(_callFromThread)
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result = queue.get()
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if isinstance(result, failure.Failure):
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# This makes it easier for the debugger to get access to the instance
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try:
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result.raiseException()
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except Exception, e:
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raise e
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return result
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#-------------------------------------------------------------------------------
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# Things for managing deferreds
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#-------------------------------------------------------------------------------
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def parseResults(results):
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"""Pull out results/Failures from a DeferredList."""
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return [x[1] for x in results]
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def gatherBoth(dlist, fireOnOneCallback=0,
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fireOnOneErrback=0,
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consumeErrors=0,
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logErrors=0):
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"""This is like gatherBoth, but sets consumeErrors=1."""
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d = DeferredList(dlist, fireOnOneCallback, fireOnOneErrback,
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consumeErrors, logErrors)
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if not fireOnOneCallback:
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d.addCallback(parseResults)
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return d
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SUCCESS = True
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FAILURE = False
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class DeferredList(defer.Deferred):
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"""I combine a group of deferreds into one callback.
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I track a list of L{Deferred}s for their callbacks, and make a single
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callback when they have all completed, a list of (success, result)
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tuples, 'success' being a boolean.
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Note that you can still use a L{Deferred} after putting it in a
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DeferredList. For example, you can suppress 'Unhandled error in Deferred'
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messages by adding errbacks to the Deferreds *after* putting them in the
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DeferredList, as a DeferredList won't swallow the errors. (Although a more
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convenient way to do this is simply to set the consumeErrors flag)
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Note: This is a modified version of the twisted.internet.defer.DeferredList
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"""
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fireOnOneCallback = 0
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fireOnOneErrback = 0
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def __init__(self, deferredList, fireOnOneCallback=0, fireOnOneErrback=0,
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consumeErrors=0, logErrors=0):
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"""Initialize a DeferredList.
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@type deferredList: C{list} of L{Deferred}s
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@param deferredList: The list of deferreds to track.
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@param fireOnOneCallback: (keyword param) a flag indicating that
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only one callback needs to be fired for me to call
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my callback
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@param fireOnOneErrback: (keyword param) a flag indicating that
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only one errback needs to be fired for me to call
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my errback
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@param consumeErrors: (keyword param) a flag indicating that any errors
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raised in the original deferreds should be
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consumed by this DeferredList. This is useful to
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prevent spurious warnings being logged.
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"""
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self.resultList = [None] * len(deferredList)
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defer.Deferred.__init__(self)
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if len(deferredList) == 0 and not fireOnOneCallback:
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self.callback(self.resultList)
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# These flags need to be set *before* attaching callbacks to the
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# deferreds, because the callbacks use these flags, and will run
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# synchronously if any of the deferreds are already fired.
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self.fireOnOneCallback = fireOnOneCallback
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self.fireOnOneErrback = fireOnOneErrback
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self.consumeErrors = consumeErrors
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self.logErrors = logErrors
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self.finishedCount = 0
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index = 0
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for deferred in deferredList:
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deferred.addCallbacks(self._cbDeferred, self._cbDeferred,
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callbackArgs=(index,SUCCESS),
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errbackArgs=(index,FAILURE))
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index = index + 1
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def _cbDeferred(self, result, index, succeeded):
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"""(internal) Callback for when one of my deferreds fires.
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"""
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self.resultList[index] = (succeeded, result)
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self.finishedCount += 1
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if not self.called:
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if succeeded == SUCCESS and self.fireOnOneCallback:
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self.callback((result, index))
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elif succeeded == FAILURE and self.fireOnOneErrback:
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# We have modified this to fire the errback chain with the actual
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# Failure instance the originally occured rather than twisted's
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# FirstError which wraps the failure
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self.errback(result)
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elif self.finishedCount == len(self.resultList):
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self.callback(self.resultList)
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if succeeded == FAILURE and self.logErrors:
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log.err(result)
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if succeeded == FAILURE and self.consumeErrors:
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result = None
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return result
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def wait_for_file(filename, delay=0.1, max_tries=10):
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"""Wait (poll) for a file to be created.
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This method returns a Deferred that will fire when a file exists. It
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works by polling os.path.isfile in time intervals specified by the
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delay argument. If `max_tries` is reached, it will errback with a
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`FileTimeoutError`.
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Parameters
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----------
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filename : str
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The name of the file to wait for.
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delay : float
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The time to wait between polls.
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max_tries : int
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The max number of attempts before raising `FileTimeoutError`
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Returns
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-------
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d : Deferred
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A Deferred instance that will fire when the file exists.
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"""
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d = defer.Deferred()
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def _test_for_file(filename, attempt=0):
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if attempt >= max_tries:
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d.errback(FileTimeoutError(
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'timeout waiting for file to be created: %s' % filename
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))
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else:
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if os.path.isfile(filename):
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d.callback(True)
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else:
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reactor.callLater(delay, _test_for_file, filename, attempt+1)
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_test_for_file(filename)
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return d
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def sleep_deferred(seconds):
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"""Sleep without blocking the event loop."""
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d = defer.Deferred()
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reactor.callLater(seconds, d.callback, seconds)
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return d
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def make_deferred(func):
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"""A decorator that calls a function with :func`maybeDeferred`."""
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def _wrapper(*args, **kwargs):
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return defer.maybeDeferred(func, *args, **kwargs)
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return _wrapper
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