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Cancellation; verbosity #2

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Cancellation; verbosity #2

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33 changes: 21 additions & 12 deletions txretry/retry.py
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Original file line number Diff line number Diff line change
Expand Up @@ -55,7 +55,7 @@ def simpleBackoffIterator(maxResults=10, maxDelay=120.0, now=True,

class RetryingCall(object):
"""
Calls a function repeatedly, passing it args and kw args. Failures are
Calls a function repeatedly, passing it *args. Failures are
passed to a user-supplied failure testing function. If the failure is
ignored, the function is called again after a delay whose duration is
obtained from a user-supplied iterator. The start method (below)
Expand All @@ -67,14 +67,15 @@ class RetryingCall(object):
@ival failures: a list of failures received in calling the function.
@param func: The function to call.
@param args: Positional arguments to pass to the function.
@param kw: Keyword arguments to pass to the function.
@param verbose: Whether to log failures.
"""
def __init__(self, func, *args, **kw):
self._func = func
self._args = args
self._kw = kw
self._start = time.time()
self.failures = []
self._verbose = kw.get("verbose", True)
self._delay_deferred = None

def _err(self, fail):
"""An errback function for the function call.
Expand All @@ -86,7 +87,7 @@ def _err(self, fail):
self.failures.append(fail)
try:
result = self._failureTester(fail)
except:
except Exception:
self._deferred.errback()
else:
if isinstance(result, failure.Failure):
Expand All @@ -95,7 +96,8 @@ def _err(self, fail):
self._deferred.errback(result)
else:
# Schedule another call.
log.msg('RetryingCall: Ignoring failure %s' % (fail,))
if self._verbose:
log.err(fail, 'RetryingCall: attempt {} failed'.format(len(self.failures)))
self._call()

def _call(self):
Expand All @@ -105,12 +107,13 @@ def _call(self):
try:
delay = self._backoffIterator.next()
except StopIteration:
log.msg('StopIteration in RetryingCall: ran out of attempts.')
if self._verbose:
log.msg('RetryingCall: ran out of attempts.')
self._deferred.errback(self.failures[0] if self.failures else None)
else:
d = task.deferLater(reactor, delay,
self._func, *self._args, **self._kw)
d.addCallbacks(self._deferred.callback, self._err)
self._delay_deferred = task.deferLater(reactor, delay,
self._func, *self._args)
self._delay_deferred.addCallbacks(self._deferred.callback, self._err)

def start(self, backoffIterator=None, failureTester=None):
"""
Expand All @@ -123,12 +126,18 @@ def start(self, backoffIterator=None, failureTester=None):
argument (a C{failure.Failure}) that we can use to check
whether a failed call should be retried.
@return: a C{Deferred} that will fire with the result of calling
self._func with self._args and self._kw as arguments, or fail
with the first failure encountered.
self._func with self._args as arguments, or fail with the
first failure encountered.
"""
self._backoffIterator = iter(backoffIterator or
simpleBackoffIterator())
self._failureTester = failureTester or (lambda _: None)
self._deferred = defer.Deferred()

def cancel(_d):
if self._delay_deferred:
self._delay_deferred.cancel()
self._deferred = defer.Deferred(cancel)

self._call()
return self._deferred