def test_init(self):
# test initializing ScheduledCall without overriding its clock
sc = ScheduledCall(self.obj.func, *self.default_args,
**self.default_kwargs)
sc.schedule()
sc.cancel()
def test_init(self):
# test initializing ScheduledCall without overriding its clock
sc = ScheduledCall(self.obj.func, *self.default_args,
**self.default_kwargs)
sc.schedule()
sc.cancel()
class ScheduledCallTest(unittest.TestCase):
default_args = (10, 'hello')
default_kwargs = {'a': 47, 'b': 'c'}
def setUp(self):
self.clock = Clock()
self.obj = ModifiedObject()
self.sc = ScheduledCall(self.obj.func, clock=self.clock,
*self.default_args,
**self.default_kwargs)
def _check(self, args, kwargs):
if args is None:
self.assertIsNone(self.obj.args)
else:
self.assertTupleEqual(self.obj.args, args)
if kwargs is None:
self.assertIsNone(self.obj.kwargs)
else:
self.assertEqual(self.obj.kwargs, kwargs)
def test_init(self):
# test initializing ScheduledCall without overriding its clock
sc = ScheduledCall(self.obj.func, *self.default_args,
**self.default_kwargs)
sc.schedule()
sc.cancel()
def test_get_time_and_is_scheduled(self):
self.clock.advance(10)
self.assertFalse(self.sc.is_scheduled())
self.assertEqual(self.sc.get_time(), 0)
self.sc.schedule(5)
self.assertTrue(self.sc.is_scheduled())
self.assertEqual(self.sc.get_time(), 15)
self.clock.advance(5)
self.assertFalse(self.sc.is_scheduled())
self.assertEqual(self.sc.get_time(), 0)
def test_no_delay(self):
self.sc.schedule()
self._check(None, None)
self.clock.advance(0)
self._check(self.default_args, self.default_kwargs)
def test_default(self):
self.assertTrue(self.sc.schedule(5))
self._check(None, None)
self.clock.advance(1)
self.assertFalse(self.sc.schedule(1))
self.clock.advance(2)
self._check(None, None)
self.clock.advance(3)
self._check(self.default_args, self.default_kwargs)
def test_cancel(self):
self.sc.schedule(5)
self.clock.advance(3)
self.sc.cancel()
self.clock.advance(3)
self._check(None, None)
self.assertTrue(self.sc.schedule(1))
self.clock.advance(1)
self._check(self.default_args, self.default_kwargs)
def test_overwrite(self):
over_args = ('crawlmi',)
over_kwargs = {'a': 50, 'd': 'e'}
self.sc.schedule(5, *over_args, **over_kwargs)
self.clock.advance(5)
self._check(over_args, over_kwargs)
def test_partial_overwrite(self):
over_args = ('crawlmi',)
self.sc.schedule(5, *over_args)
self.clock.advance(5)
self._check(over_args, {})
def test_nested_schedule(self):
def func(*args, **kwargs):
self.obj.func(*args, **kwargs)
self.sc.schedule()
self.sc.func = func
self.sc.schedule()
self.assertEqual(self.obj.num_calls, 0)
self.clock.advance(0)
self.assertEqual(self.obj.num_calls, 1)
self.clock.advance(0)
self.assertEqual(self.obj.num_calls, 2)
def test_nested_schedule_delay(self):
args1 = ('a',)
kwargs1 = {'a': 'b'}
args2 = ('b',)
kwargs2 = {'b': 'c'}
def func(*args, **kwargs):
self.obj.func(*args, **kwargs)
self.sc.schedule(4, *args2, **kwargs2)
self.sc.func = func
self.sc.schedule(3, *args1, **kwargs1)
self.clock.advance(3)
self.assertIsNotNone(self.sc._call)
self._check(args1, kwargs1)
self.clock.advance(3)
self._check(args1, kwargs1)
self.clock.advance(1)
self._check(args2, kwargs2)
class ScheduledCallTest(unittest.TestCase):
default_args = (10, 'hello')
default_kwargs = {'a': 47, 'b': 'c'}
def setUp(self):
self.clock = Clock()
self.obj = ModifiedObject()
self.sc = ScheduledCall(self.obj.func,
clock=self.clock,
*self.default_args,
**self.default_kwargs)
def _check(self, args, kwargs):
if args is None:
self.assertIsNone(self.obj.args)
else:
self.assertTupleEqual(self.obj.args, args)
if kwargs is None:
self.assertIsNone(self.obj.kwargs)
else:
self.assertEqual(self.obj.kwargs, kwargs)
def test_init(self):
# test initializing ScheduledCall without overriding its clock
sc = ScheduledCall(self.obj.func, *self.default_args,
**self.default_kwargs)
sc.schedule()
sc.cancel()
def test_get_time_and_is_scheduled(self):
self.clock.advance(10)
self.assertFalse(self.sc.is_scheduled())
self.assertEqual(self.sc.get_time(), 0)
self.sc.schedule(5)
self.assertTrue(self.sc.is_scheduled())
self.assertEqual(self.sc.get_time(), 15)
self.clock.advance(5)
self.assertFalse(self.sc.is_scheduled())
self.assertEqual(self.sc.get_time(), 0)
def test_no_delay(self):
self.sc.schedule()
self._check(None, None)
self.clock.advance(0)
self._check(self.default_args, self.default_kwargs)
def test_default(self):
self.assertTrue(self.sc.schedule(5))
self._check(None, None)
self.clock.advance(1)
self.assertFalse(self.sc.schedule(1))
self.clock.advance(2)
self._check(None, None)
self.clock.advance(3)
self._check(self.default_args, self.default_kwargs)
def test_cancel(self):
self.sc.schedule(5)
self.clock.advance(3)
self.sc.cancel()
self.clock.advance(3)
self._check(None, None)
self.assertTrue(self.sc.schedule(1))
self.clock.advance(1)
self._check(self.default_args, self.default_kwargs)
def test_overwrite(self):
over_args = ('crawlmi', )
over_kwargs = {'a': 50, 'd': 'e'}
self.sc.schedule(5, *over_args, **over_kwargs)
self.clock.advance(5)
self._check(over_args, over_kwargs)
def test_partial_overwrite(self):
over_args = ('crawlmi', )
self.sc.schedule(5, *over_args)
self.clock.advance(5)
self._check(over_args, {})
def test_nested_schedule(self):
def func(*args, **kwargs):
self.obj.func(*args, **kwargs)
self.sc.schedule()
self.sc.func = func
self.sc.schedule()
self.assertEqual(self.obj.num_calls, 0)
self.clock.advance(0)
self.assertEqual(self.obj.num_calls, 1)
self.clock.advance(0)
self.assertEqual(self.obj.num_calls, 2)
def test_nested_schedule_delay(self):
args1 = ('a', )
kwargs1 = {'a': 'b'}
args2 = ('b', )
kwargs2 = {'b': 'c'}
def func(*args, **kwargs):
self.obj.func(*args, **kwargs)
self.sc.schedule(4, *args2, **kwargs2)
self.sc.func = func
self.sc.schedule(3, *args1, **kwargs1)
self.clock.advance(3)
self.assertIsNotNone(self.sc._call)
self._check(args1, kwargs1)
self.clock.advance(3)
self._check(args1, kwargs1)
self.clock.advance(1)
self._check(args2, kwargs2)
class Slot(object):
'''Slot represents a queue of requests for one particular domain.
It respects both DOWNLOAD_DELAY and CONCURRENT_REQUESTS_PER_DOMAIN.
'''
def __init__(self, download_handler, concurrency, delay, randomize_delay,
clock=None):
self.download_handler = download_handler
self.concurrency = concurrency
self.delay = delay
self.randomize_delay = randomize_delay
self.in_progress = set() # request waiting to be downloaded
self.transferring = set() # requests being downloaded (subset of `in_progress`)
self.last_download_time = 0
self.queue = MemoryQueue() # queue of (request, deferred)
# clock is used in unittests
self.clock = clock or reactor
self.delayed_processing = ScheduledCall(self._process, clock=self.clock)
def enqueue(self, request, dfd):
'''Main entry point.
Put the new request to the queue and if possible, start downloading it.
'''
def remove_in_progress(response):
self.in_progress.remove(request)
return response
self.in_progress.add(request)
dfd.addBoth(remove_in_progress)
self.queue.push((request, dfd))
self._process()
@property
def free_slots(self):
return self.concurrency - len(self.transferring)
def is_idle(self):
return len(self.in_progress) == 0
def _process(self):
'''Process the requests in the queue, while respecting the delay and
concurrency.
'''
if self.delayed_processing.is_scheduled() or self._schedule_delay():
return
while self.queue and self.free_slots > 0:
self.last_download_time = self.clock.seconds()
request, downloaded_dfd = self.queue.pop()
dfd = self._download(request)
dfd.chainDeferred(downloaded_dfd)
if self._schedule_delay():
return
def _schedule_delay(self):
if self.delay:
penalty = (self.last_download_time + self.get_download_delay() -
self.clock.seconds())
if penalty > 0:
# following schedule should always be successfull, because
# `_schedule_delay()` is only called from within `_process()`
self.delayed_processing.schedule(penalty)
return True
return False
def _download(self, request):
dfd = defer.succeed(request)
# download the response
dfd.addCallback(self.download_handler.download_request)
# it is VERY important to wrap the failure into a new object!
# For errors like ConnectionLost, the same Failure object is returned
# everytime and we cannot use 'failure.request' field.
def wrap_failure(failure):
return Failure(failure.value)
dfd.addErrback(wrap_failure)
# put the request into the set of `transferring` to block other requests
# after the response is downloaded, remove it from `transferring`
def remove_transferring(response):
self.transferring.remove(request)
self._process() # process unblocked requests
return response
self.transferring.add(request)
dfd.addBoth(remove_transferring)
return dfd
def get_download_delay(self):
if self.randomize_delay:
return random.uniform(0.5 * self.delay, 1.5 * self.delay)
return self.delay
class Engine(object):
'''
WARNING: don't stop() and start() engine. Use pause() and unpause(),
instead.
'''
# how many seconds to wait between the checks of response_queue
QUEUE_CHECK_FREQUENCY = 0.1
# how often to check is still paused
PAUSED_CHECK_FREQUENCY = 5
# how often to check if being idle
IDLE_CHECK_FREQUENCY = 5
def __init__(self, settings, project, command_invoked='', clock=None):
'''Constructor of Engine should be very lightweight, so that things
can be easily unittested. For any more complicated initialization
use `setup()`.
'''
self.settings = settings
self.project = project
self.spiders = SpiderManager(settings)
self.stop_if_idle = True
self.initialized = False # True, when `setup()` has been called
# name of the command invoking the engine. E.g. `crawl`, `shell`, etc.
self.command_invoked = command_invoked
self.spider = None
self.pending_requests = 0
self.running = False
self.paused = False
# clock is used in unittests
self.clock = clock or reactor
self.processing = ScheduledCall(self._process_queue, clock=self.clock)
def set_spider(self, spider):
self.spider = spider
self.settings.spider_settings = spider.spider_settings()
def setup(self):
assert self.spider is not None, 'Spider is not set in Engine.'
# IMPORTANT: order of the following initializations is very important
# so please, think twice about any changes to it
# initialize logging
if self.settings.get_bool('LOG_ENABLED'):
log.start(
self.settings['LOG_FILE'],
self.settings['LOG_LEVEL'],
self.settings['LOG_STDOUT'],
self.settings['LOG_ENCODING'])
# initialize signals
self.signals = SignalManager(self)
#initialize stats
stats_cls = load_object(self.settings.get('STATS_CLASS'))
self.stats = stats_cls(self)
# initialize downloader
self.request_queue = PriorityQueue(lambda _: MemoryQueue())
self.response_queue = ResponseQueue(
self.settings.get_int('RESPONSE_ACTIVE_SIZE_LIMIT'))
self.downloader = Downloader(self.settings, self.request_queue,
self.response_queue, clock=self.clock)
# initialize extensions
self.extensions = ExtensionManager(self)
# initialize downloader pipeline
self.pipeline = PipelineManager(self)
self.initialized = True
# now that everything is ready, set the spider's engine
self.spider.set_engine(self)
def crawl_start_requests(self):
# process start requests from spider
try:
requests = self.spider.start_requests()
for req in arg_to_iter(requests):
self.download(req)
except:
log.err(Failure(), 'Error when processing start requests.')
def start(self):
assert self.initialized, 'Engine is not initialized. Call `setup()` to initialize it.'
self.start_time = time()
self.running = True
self.signals.send(signal=signals.engine_started)
self.processing.schedule(self.QUEUE_CHECK_FREQUENCY)
def stop(self, reason=''):
assert self.running, 'Engine is not running.'
self.running = False
def _stop(_):
self.processing.cancel()
self.downloader.close()
self.request_queue.close()
self.response_queue.close()
log.msg(format='Engine stopped (%(reason)s)', reason=reason)
self.signals.send(signal=signals.engine_stopped, reason=reason)
self.stats.dump_stats()
dfd = defer_succeed(reason, clock=self.clock)
dfd.addBoth(_stop)
return dfd
def pause(self):
self.paused = True
def unpause(self):
self.paused = False
def download(self, request):
'''"Download" the given request. First pass it through the downloader
pipeline.
- if the request is received, push it to `request_queue`
- if the response is received , push it to `response_queue`
'''
def _success(request_or_response):
if isinstance(request_or_response, Request):
self.signals.send(signal=signals.request_received,
request=request_or_response)
if self.running:
self.request_queue.push(request_or_response.priority,
request_or_response)
elif isinstance(request_or_response, Response):
request_or_response.request = request
if self.running:
self.response_queue.push(request_or_response)
def _failure(failure):
failure.request = request
dfd = defer_fail(failure, clock=self.clock)
dfd.addBoth(self._handle_pipeline_result)
dfd.addBoth(self._finalize_download)
return dfd
self.pending_requests += 1
d = defer_succeed(request, clock=self.clock)
d.addCallback(self.pipeline.process_request)
d.addCallbacks(_success, _failure)
return d
def is_idle(self):
return self.pending_requests == 0 and len(self.response_queue) == 0
def _process_queue(self):
if not self.running:
return
elif self.paused:
self.processing.schedule(self.PAUSED_CHECK_FREQUENCY)
elif self.response_queue:
response = self.response_queue.pop()
if isinstance(response, Response):
self.signals.send(signal=signals.response_downloaded,
response=response)
dfd = defer_result(response, clock=self.clock)
dfd.addBoth(self.pipeline.process_response)
dfd.addBoth(self._handle_pipeline_result)
dfd.addBoth(self._finalize_download)
dfd.addBoth(lambda _: self.processing.schedule(0))
elif self.is_idle():
# send `spider_idle` signal
res = self.signals.send(signal=signals.spider_idle,
dont_log=DontStopEngine)
dont_stop = any(isinstance(x, Failure) and
isinstance(x.value, DontStopEngine)
for _, x in res)
# more requests have been scheduled
if not self.is_idle():
self.processing.schedule(0)
# slow down a little, but still run
elif dont_stop or not self.stop_if_idle:
self.processing.schedule(self.IDLE_CHECK_FREQUENCY)
else:
self.stop('finished')
else:
self.processing.schedule(self.QUEUE_CHECK_FREQUENCY)
def _finalize_download(self, _):
self.pending_requests -= 1
def _handle_pipeline_result(self, result):
if result is None:
pass
elif isinstance(result, Request):
self.download(result)
else:
assert isinstance(result, (Response, Failure))
request = result.request
if isinstance(result, Response):
flags = ' %s' % result.flags if result.flags else ''
log.msg(format='Crawled %(url)s [%(status)s]%(flags)s',
level=log.DEBUG, url=result.url, status=result.status,
flags=flags)
self.signals.send(signal=signals.response_received,
response=result)
else:
self.signals.send(signal=signals.failure_received,
failure=result)
dfd = defer_result(result, clock=self.clock)
dfd.addCallbacks(request.callback or self.spider.parse,
request.errback)
dfd.addCallbacks(
self._handle_spider_output,
self._handle_spider_error,
callbackKeywords={'request': request},
errbackKeywords={'request': request})
return dfd
def _handle_spider_output(self, result, request):
result = arg_to_iter(result)
for request in result:
assert isinstance(request, Request), \
'spider must return None, request or iterable of requests'
self.download(request)
def _handle_spider_error(self, failure, request):
error = failure.value
if isinstance(error, StopEngine):
self.stop(error.reason)
return
# set `request` in a case the error was raised inside the spider
failure.request = request
self.signals.send(signal=signals.spider_error, failure=failure)
if not getattr(failure.value, 'quiet', False):
log.err(failure, 'Error when downloading %s' % request)
def __str__(self):
return '<%s at 0x%0x>' % (type(self).__name__, id(self))
__repr__ = __str__
class Engine(object):
'''
WARNING: don't stop() and start() engine. Use pause() and unpause(),
instead.
'''
# how many seconds to wait between the checks of response_queue
QUEUE_CHECK_FREQUENCY = 0.1
# how often to check is still paused
PAUSED_CHECK_FREQUENCY = 5
# how often to check if being idle
IDLE_CHECK_FREQUENCY = 5
def __init__(self, settings, project, command_invoked='', clock=None):
'''Constructor of Engine should be very lightweight, so that things
can be easily unittested. For any more complicated initialization
use `setup()`.
'''
self.settings = settings
self.project = project
self.spiders = SpiderManager(settings)
self.stop_if_idle = True
self.initialized = False # True, when `setup()` has been called
# name of the command invoking the engine. E.g. `crawl`, `shell`, etc.
self.command_invoked = command_invoked
self.spider = None
self.pending_requests = 0
self.running = False
self.paused = False
# clock is used in unittests
self.clock = clock or reactor
self.processing = ScheduledCall(self._process_queue, clock=self.clock)
def set_spider(self, spider):
self.spider = spider
self.settings.spider_settings = spider.spider_settings()
def setup(self):
assert self.spider is not None, 'Spider is not set in Engine.'
# IMPORTANT: order of the following initializations is very important
# so please, think twice about any changes to it
# initialize logging
if self.settings.get_bool('LOG_ENABLED'):
log.start(self.settings['LOG_FILE'], self.settings['LOG_LEVEL'],
self.settings['LOG_STDOUT'],
self.settings['LOG_ENCODING'])
# initialize signals
self.signals = SignalManager(self)
#initialize stats
stats_cls = load_object(self.settings.get('STATS_CLASS'))
self.stats = stats_cls(self)
# initialize downloader
self.request_queue = PriorityQueue(lambda _: MemoryQueue())
self.response_queue = ResponseQueue(
self.settings.get_int('RESPONSE_ACTIVE_SIZE_LIMIT'))
self.downloader = Downloader(self.settings,
self.request_queue,
self.response_queue,
clock=self.clock)
# initialize extensions
self.extensions = ExtensionManager(self)
# initialize downloader pipeline
self.pipeline = PipelineManager(self)
self.initialized = True
# now that everything is ready, set the spider's engine
self.spider.set_engine(self)
def crawl_start_requests(self):
# process start requests from spider
try:
requests = self.spider.start_requests()
for req in arg_to_iter(requests):
self.download(req)
except:
log.err(Failure(), 'Error when processing start requests.')
def start(self):
assert self.initialized, 'Engine is not initialized. Call `setup()` to initialize it.'
self.start_time = time()
self.running = True
self.signals.send(signal=signals.engine_started)
self.processing.schedule(self.QUEUE_CHECK_FREQUENCY)
def stop(self, reason=''):
assert self.running, 'Engine is not running.'
self.running = False
def _stop(_):
self.processing.cancel()
self.downloader.close()
self.request_queue.close()
self.response_queue.close()
log.msg(format='Engine stopped (%(reason)s)', reason=reason)
self.signals.send(signal=signals.engine_stopped, reason=reason)
self.stats.dump_stats()
dfd = defer_succeed(reason, clock=self.clock)
dfd.addBoth(_stop)
return dfd
def pause(self):
self.paused = True
def unpause(self):
self.paused = False
def download(self, request):
'''"Download" the given request. First pass it through the downloader
pipeline.
- if the request is received, push it to `request_queue`
- if the response is received , push it to `response_queue`
'''
def _success(request_or_response):
if isinstance(request_or_response, Request):
self.signals.send(signal=signals.request_received,
request=request_or_response)
if self.running:
self.request_queue.push(request_or_response.priority,
request_or_response)
elif isinstance(request_or_response, Response):
request_or_response.request = request
if self.running:
self.response_queue.push(request_or_response)
def _failure(failure):
failure.request = request
dfd = defer_fail(failure, clock=self.clock)
dfd.addBoth(self._handle_pipeline_result)
dfd.addBoth(self._finalize_download)
return dfd
self.pending_requests += 1
d = defer_succeed(request, clock=self.clock)
d.addCallback(self.pipeline.process_request)
d.addCallbacks(_success, _failure)
return d
def is_idle(self):
return self.pending_requests == 0 and len(self.response_queue) == 0
def _process_queue(self):
if not self.running:
return
elif self.paused:
self.processing.schedule(self.PAUSED_CHECK_FREQUENCY)
elif self.response_queue:
response = self.response_queue.pop()
if isinstance(response, Response):
self.signals.send(signal=signals.response_downloaded,
response=response)
dfd = defer_result(response, clock=self.clock)
dfd.addBoth(self.pipeline.process_response)
dfd.addBoth(self._handle_pipeline_result)
dfd.addBoth(self._finalize_download)
dfd.addBoth(lambda _: self.processing.schedule(0))
elif self.is_idle():
# send `spider_idle` signal
res = self.signals.send(signal=signals.spider_idle,
dont_log=DontStopEngine)
dont_stop = any(
isinstance(x, Failure) and isinstance(x.value, DontStopEngine)
for _, x in res)
# more requests have been scheduled
if not self.is_idle():
self.processing.schedule(0)
# slow down a little, but still run
elif dont_stop or not self.stop_if_idle:
self.processing.schedule(self.IDLE_CHECK_FREQUENCY)
else:
self.stop('finished')
else:
self.processing.schedule(self.QUEUE_CHECK_FREQUENCY)
def _finalize_download(self, _):
self.pending_requests -= 1
def _handle_pipeline_result(self, result):
if result is None:
pass
elif isinstance(result, Request):
self.download(result)
else:
assert isinstance(result, (Response, Failure))
request = result.request
if isinstance(result, Response):
flags = ' %s' % result.flags if result.flags else ''
log.msg(format='Crawled %(url)s [%(status)s]%(flags)s',
level=log.DEBUG,
url=result.url,
status=result.status,
flags=flags)
self.signals.send(signal=signals.response_received,
response=result)
else:
self.signals.send(signal=signals.failure_received,
failure=result)
dfd = defer_result(result, clock=self.clock)
dfd.addCallbacks(request.callback or self.spider.parse,
request.errback)
dfd.addCallbacks(self._handle_spider_output,
self._handle_spider_error,
callbackKeywords={'request': request},
errbackKeywords={'request': request})
return dfd
def _handle_spider_output(self, result, request):
result = arg_to_iter(result)
for request in result:
assert isinstance(request, Request), \
'spider must return None, request or iterable of requests'
self.download(request)
def _handle_spider_error(self, failure, request):
error = failure.value
if isinstance(error, StopEngine):
self.stop(error.reason)
return
# set `request` in a case the error was raised inside the spider
failure.request = request
self.signals.send(signal=signals.spider_error, failure=failure)
if not getattr(failure.value, 'quiet', False):
log.err(failure, 'Error when downloading %s' % request)
def __str__(self):
return '<%s at 0x%0x>' % (type(self).__name__, id(self))
__repr__ = __str__
class Slot(object):
'''Slot represents a queue of requests for one particular domain.
It respects both DOWNLOAD_DELAY and CONCURRENT_REQUESTS_PER_DOMAIN.
'''
def __init__(self, download_handler, concurrency, delay, randomize_delay,
clock=None):
self.download_handler = download_handler
self.concurrency = concurrency
self.delay = delay
self.randomize_delay = randomize_delay
self.in_progress = set() # request waiting to be downloaded
self.transferring = set() # requests being downloaded (subset of `in_progress`)
self.last_download_time = 0
self.queue = MemoryQueue() # queue of (request, deferred)
# clock is used in unittests
self.clock = clock or reactor
self.delayed_processing = ScheduledCall(self._process, clock=self.clock)
def enqueue(self, request, dfd):
'''Main entry point.
Put the new request to the queue and if possible, start downloading it.
'''
def remove_in_progress(response):
self.in_progress.remove(request)
return response
self.in_progress.add(request)
dfd.addBoth(remove_in_progress)
self.queue.push((request, dfd))
self._process()
@property
def free_slots(self):
return self.concurrency - len(self.transferring)
def is_idle(self):
return len(self.in_progress) == 0
def _process(self):
'''Process the requests in the queue, while respecting the delay and
concurrency.
'''
if self.delayed_processing.is_scheduled() or self._schedule_delay():
return
while self.queue and self.free_slots > 0:
self.last_download_time = self.clock.seconds()
request, downloaded_dfd = self.queue.pop()
dfd = self._download(request)
dfd.chainDeferred(downloaded_dfd)
if self._schedule_delay():
return
def _schedule_delay(self):
if self.delay:
penalty = (self.last_download_time + self.get_download_delay() -
self.clock.seconds())
if penalty > 0:
# following schedule should always be successfull, because
# `_schedule_delay()` is only called from within `_process()`
self.delayed_processing.schedule(penalty)
return True
return False
def _download(self, request):
dfd = defer.succeed(request)
# download the response
dfd.addCallback(self.download_handler.download_request)
# it is VERY important to wrap the failure into a new object!
# For errors like ConnectionLost, the same Failure object is returned
# everytime and we cannot use 'failure.request' field.
def wrap_failure(failure):
return Failure(failure.value)
dfd.addErrback(wrap_failure)
# put the request into the set of `transferring` to block other requests
# after the response is downloaded, remove it from `transferring`
def remove_transferring(response):
self.transferring.remove(request)
self._process() # process unblocked requests
return response
self.transferring.add(request)
dfd.addBoth(remove_transferring)
return dfd
def get_download_delay(self):
if self.randomize_delay:
return random.uniform(0.5 * self.delay, 1.5 * self.delay)
return self.delay