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from __future__ import absolute_import
import random
import warnings
from time import time
from datetime import datetime
from collections import deque
import six
from twisted.internet import reactor, defer, task
from scrapy.utils.defer import mustbe_deferred
from scrapy.utils.httpobj import urlparse_cached
from scrapy.resolver import dnscache
from scrapy import signals
from .middleware import DownloaderMiddlewareManager
from .handlers import DownloadHandlers
class Slot(object):
"""Downloader slot"""
def __init__(self, concurrency, delay, randomize_delay):
self.concurrency = concurrency
self.delay = delay
self.randomize_delay = randomize_delay
self.active = set()
self.queue = deque()
self.transferring = set()
self.lastseen = 0
self.latercall = None
def free_transfer_slots(self):
return self.concurrency - len(self.transferring)
def download_delay(self):
if self.randomize_delay:
return random.uniform(0.5 * self.delay, 1.5 * self.delay)
return self.delay
def close(self):
if self.latercall and self.latercall.active():
self.latercall.cancel()
def __repr__(self):
cls_name = self.__class__.__name__
return "%s(concurrency=%r, delay=%0.2f, randomize_delay=%r)" % (
cls_name, self.concurrency, self.delay, self.randomize_delay)
def __str__(self):
return (
"<downloader.Slot concurrency=%r delay=%0.2f randomize_delay=%r "
"len(active)=%d len(queue)=%d len(transferring)=%d lastseen=%s>" % (
self.concurrency, self.delay, self.randomize_delay,
len(self.active), len(self.queue), len(self.transferring),
datetime.fromtimestamp(self.lastseen).isoformat()
)
)
def _get_concurrency_delay(concurrency, spider, settings):
delay = settings.getfloat('DOWNLOAD_DELAY')
if hasattr(spider, 'DOWNLOAD_DELAY'):
warnings.warn("%s.DOWNLOAD_DELAY attribute is deprecated, use %s.download_delay instead" %
(type(spider).__name__, type(spider).__name__))
delay = spider.DOWNLOAD_DELAY
if hasattr(spider, 'download_delay'):
delay = spider.download_delay
if hasattr(spider, 'max_concurrent_requests'):
concurrency = spider.max_concurrent_requests
return concurrency, delay
class Downloader(object):
def __init__(self, crawler):
self.settings = crawler.settings
self.signals = crawler.signals
self.slots = {}
self.active = set()
self.handlers = DownloadHandlers(crawler)
self.total_concurrency = self.settings.getint('CONCURRENT_REQUESTS')
self.domain_concurrency = self.settings.getint('CONCURRENT_REQUESTS_PER_DOMAIN')
self.ip_concurrency = self.settings.getint('CONCURRENT_REQUESTS_PER_IP')
self.randomize_delay = self.settings.getbool('RANDOMIZE_DOWNLOAD_DELAY')
self.middleware = DownloaderMiddlewareManager.from_crawler(crawler)
self._slot_gc_loop = task.LoopingCall(self._slot_gc)
self._slot_gc_loop.start(60)
def fetch(self, request, spider):
def _deactivate(response):
self.active.remove(request)
return response
self.active.add(request)
dfd = self.middleware.download(self._enqueue_request, request, spider)
return dfd.addBoth(_deactivate)
def needs_backout(self):
return len(self.active) >= self.total_concurrency
def _get_slot(self, request, spider):
key = self._get_slot_key(request, spider)
if key not in self.slots:
conc = self.ip_concurrency if self.ip_concurrency else self.domain_concurrency
conc, delay = _get_concurrency_delay(conc, spider, self.settings)
self.slots[key] = Slot(conc, delay, self.randomize_delay)
return key, self.slots[key]
def _get_slot_key(self, request, spider):
if 'download_slot' in request.meta:
return request.meta['download_slot']
key = urlparse_cached(request).hostname or ''
if self.ip_concurrency:
key = dnscache.get(key, key)
return key
def _enqueue_request(self, request, spider):
key, slot = self._get_slot(request, spider)
request.meta['download_slot'] = key
def _deactivate(response):
slot.active.remove(request)
return response
slot.active.add(request)
deferred = defer.Deferred().addBoth(_deactivate)
slot.queue.append((request, deferred))
self._process_queue(spider, slot)
return deferred
def _process_queue(self, spider, slot):
if slot.latercall and slot.latercall.active():
return
# Delay queue processing if a download_delay is configured
now = time()
delay = slot.download_delay()
if delay:
penalty = delay - now + slot.lastseen
if penalty > 0:
slot.latercall = reactor.callLater(penalty, self._process_queue, spider, slot)
return
# Process enqueued requests if there are free slots to transfer for this slot
while slot.queue and slot.free_transfer_slots() > 0:
slot.lastseen = now
request, deferred = slot.queue.popleft()
dfd = self._download(slot, request, spider)
dfd.chainDeferred(deferred)
# prevent burst if inter-request delays were configured
if delay:
self._process_queue(spider, slot)
break
def _download(self, slot, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. Notify response_downloaded listeners about the recent download
# before querying queue for next request
def _downloaded(response):
self.signals.send_catch_log(signal=signals.response_downloaded,
response=response,
request=request,
spider=spider)
return response
dfd.addCallback(_downloaded)
# 3. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
slot.transferring.add(request)
def finish_transferring(_):
slot.transferring.remove(request)
self._process_queue(spider, slot)
return _
return dfd.addBoth(finish_transferring)
def close(self):
self._slot_gc_loop.stop()
for slot in six.itervalues(self.slots):
slot.close()
def _slot_gc(self, age=60):
mintime = time() - age
for key, slot in list(self.slots.items()):
if not slot.active and slot.lastseen + slot.delay < mintime:
self.slots.pop(key).close()
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