mirror of https://github.com/scrapy/scrapy.git
361 lines
13 KiB
Python
361 lines
13 KiB
Python
"""
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This is the Scrapy engine which controls the Scheduler, Downloader and Spiders.
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For more information see docs/topics/architecture.rst
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"""
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import logging
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from time import time
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from twisted.internet import defer, task
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from twisted.python.failure import Failure
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from scrapy import signals
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from scrapy.core.scraper import Scraper
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from scrapy.exceptions import DontCloseSpider
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from scrapy.http import Response, Request
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from scrapy.utils.misc import load_object
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from scrapy.utils.reactor import CallLaterOnce
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from scrapy.utils.log import logformatter_adapter, failure_to_exc_info
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logger = logging.getLogger(__name__)
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class Slot:
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def __init__(self, start_requests, close_if_idle, nextcall, scheduler):
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self.closing = False
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self.inprogress = set() # requests in progress
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self.start_requests = iter(start_requests)
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self.close_if_idle = close_if_idle
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self.nextcall = nextcall
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self.scheduler = scheduler
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self.heartbeat = task.LoopingCall(nextcall.schedule)
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def add_request(self, request):
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self.inprogress.add(request)
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def remove_request(self, request):
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self.inprogress.remove(request)
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self._maybe_fire_closing()
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def close(self):
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self.closing = defer.Deferred()
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self._maybe_fire_closing()
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return self.closing
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def _maybe_fire_closing(self):
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if self.closing and not self.inprogress:
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if self.nextcall:
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self.nextcall.cancel()
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if self.heartbeat.running:
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self.heartbeat.stop()
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self.closing.callback(None)
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class ExecutionEngine:
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def __init__(self, crawler, spider_closed_callback):
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self.crawler = crawler
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self.settings = crawler.settings
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self.signals = crawler.signals
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self.logformatter = crawler.logformatter
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self.slot = None
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self.spider = None
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self.running = False
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self.paused = False
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self.scheduler_cls = load_object(self.settings['SCHEDULER'])
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downloader_cls = load_object(self.settings['DOWNLOADER'])
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self.downloader = downloader_cls(crawler)
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self.scraper = Scraper(crawler)
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self._spider_closed_callback = spider_closed_callback
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@defer.inlineCallbacks
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def start(self):
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"""Start the execution engine"""
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if self.running:
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raise RuntimeError("Engine already running")
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self.start_time = time()
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yield self.signals.send_catch_log_deferred(signal=signals.engine_started)
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self.running = True
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self._closewait = defer.Deferred()
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yield self._closewait
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def stop(self):
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"""Stop the execution engine gracefully"""
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if not self.running:
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raise RuntimeError("Engine not running")
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self.running = False
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dfd = self._close_all_spiders()
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return dfd.addBoth(lambda _: self._finish_stopping_engine())
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def close(self):
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"""Close the execution engine gracefully.
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If it has already been started, stop it. In all cases, close all spiders
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and the downloader.
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"""
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if self.running:
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# Will also close spiders and downloader
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return self.stop()
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elif self.open_spiders:
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# Will also close downloader
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return self._close_all_spiders()
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else:
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return defer.succeed(self.downloader.close())
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def pause(self):
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"""Pause the execution engine"""
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self.paused = True
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def unpause(self):
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"""Resume the execution engine"""
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self.paused = False
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def _next_request(self, spider):
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slot = self.slot
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if not slot:
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return
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if self.paused:
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return
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while not self._needs_backout(spider):
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if not self._next_request_from_scheduler(spider):
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break
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if slot.start_requests and not self._needs_backout(spider):
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try:
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request = next(slot.start_requests)
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except StopIteration:
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slot.start_requests = None
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except Exception:
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slot.start_requests = None
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logger.error('Error while obtaining start requests',
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exc_info=True, extra={'spider': spider})
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else:
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self.crawl(request, spider)
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if self.spider_is_idle(spider) and slot.close_if_idle:
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self._spider_idle(spider)
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def _needs_backout(self, spider):
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slot = self.slot
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return (
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not self.running
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or slot.closing
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or self.downloader.needs_backout()
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or self.scraper.slot.needs_backout()
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)
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def _next_request_from_scheduler(self, spider):
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slot = self.slot
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request = slot.scheduler.next_request()
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if not request:
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return
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d = self._download(request, spider)
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d.addBoth(self._handle_downloader_output, request, spider)
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d.addErrback(lambda f: logger.info('Error while handling downloader output',
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exc_info=failure_to_exc_info(f),
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extra={'spider': spider}))
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d.addBoth(lambda _: slot.remove_request(request))
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d.addErrback(lambda f: logger.info('Error while removing request from slot',
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exc_info=failure_to_exc_info(f),
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extra={'spider': spider}))
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d.addBoth(lambda _: slot.nextcall.schedule())
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d.addErrback(lambda f: logger.info('Error while scheduling new request',
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exc_info=failure_to_exc_info(f),
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extra={'spider': spider}))
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return d
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def _handle_downloader_output(self, response, request, spider):
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if not isinstance(response, (Request, Response, Failure)):
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raise TypeError(
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"Incorrect type: expected Request, Response or Failure, got "
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f"{type(response)}: {response!r}"
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)
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# downloader middleware can return requests (for example, redirects)
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if isinstance(response, Request):
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self.crawl(response, spider)
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return
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# response is a Response or Failure
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d = self.scraper.enqueue_scrape(response, request, spider)
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d.addErrback(lambda f: logger.error('Error while enqueuing downloader output',
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exc_info=failure_to_exc_info(f),
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extra={'spider': spider}))
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return d
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def spider_is_idle(self, spider):
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if not self.scraper.slot.is_idle():
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# scraper is not idle
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return False
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if self.downloader.active:
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# downloader has pending requests
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return False
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if self.slot.start_requests is not None:
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# not all start requests are handled
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return False
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if self.slot.scheduler.has_pending_requests():
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# scheduler has pending requests
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return False
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return True
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@property
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def open_spiders(self):
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return [self.spider] if self.spider else []
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def has_capacity(self):
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"""Does the engine have capacity to handle more spiders"""
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return not bool(self.slot)
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def crawl(self, request, spider):
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if spider not in self.open_spiders:
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raise RuntimeError(f"Spider {spider.name!r} not opened when crawling: {request}")
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self.schedule(request, spider)
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self.slot.nextcall.schedule()
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def schedule(self, request, spider):
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self.signals.send_catch_log(signals.request_scheduled, request=request, spider=spider)
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if not self.slot.scheduler.enqueue_request(request):
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self.signals.send_catch_log(signals.request_dropped, request=request, spider=spider)
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def download(self, request, spider):
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d = self._download(request, spider)
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d.addBoth(self._downloaded, self.slot, request, spider)
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return d
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def _downloaded(self, response, slot, request, spider):
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slot.remove_request(request)
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return self.download(response, spider) if isinstance(response, Request) else response
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def _download(self, request, spider):
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slot = self.slot
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slot.add_request(request)
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def _on_success(response):
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if not isinstance(response, (Response, Request)):
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raise TypeError(
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"Incorrect type: expected Response or Request, got "
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f"{type(response)}: {response!r}"
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)
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if isinstance(response, Response):
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if response.request is None:
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response.request = request
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logkws = self.logformatter.crawled(response.request, response, spider)
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if logkws is not None:
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logger.log(*logformatter_adapter(logkws), extra={'spider': spider})
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self.signals.send_catch_log(
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signal=signals.response_received,
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response=response,
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request=response.request,
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spider=spider,
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)
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return response
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def _on_complete(_):
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slot.nextcall.schedule()
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return _
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dwld = self.downloader.fetch(request, spider)
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dwld.addCallbacks(_on_success)
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dwld.addBoth(_on_complete)
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return dwld
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@defer.inlineCallbacks
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def open_spider(self, spider, start_requests=(), close_if_idle=True):
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if not self.has_capacity():
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raise RuntimeError(f"No free spider slot when opening {spider.name!r}")
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logger.info("Spider opened", extra={'spider': spider})
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nextcall = CallLaterOnce(self._next_request, spider)
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scheduler = self.scheduler_cls.from_crawler(self.crawler)
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start_requests = yield self.scraper.spidermw.process_start_requests(start_requests, spider)
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slot = Slot(start_requests, close_if_idle, nextcall, scheduler)
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self.slot = slot
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self.spider = spider
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yield scheduler.open(spider)
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yield self.scraper.open_spider(spider)
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self.crawler.stats.open_spider(spider)
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yield self.signals.send_catch_log_deferred(signals.spider_opened, spider=spider)
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slot.nextcall.schedule()
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slot.heartbeat.start(5)
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def _spider_idle(self, spider):
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"""Called when a spider gets idle. This function is called when there
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are no remaining pages to download or schedule. It can be called
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multiple times. If some extension raises a DontCloseSpider exception
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(in the spider_idle signal handler) the spider is not closed until the
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next loop and this function is guaranteed to be called (at least) once
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again for this spider.
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"""
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res = self.signals.send_catch_log(signals.spider_idle, spider=spider, dont_log=DontCloseSpider)
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if any(isinstance(x, Failure) and isinstance(x.value, DontCloseSpider) for _, x in res):
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return
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if self.spider_is_idle(spider):
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self.close_spider(spider, reason='finished')
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def close_spider(self, spider, reason='cancelled'):
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"""Close (cancel) spider and clear all its outstanding requests"""
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slot = self.slot
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if slot.closing:
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return slot.closing
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logger.info("Closing spider (%(reason)s)",
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{'reason': reason},
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extra={'spider': spider})
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dfd = slot.close()
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def log_failure(msg):
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def errback(failure):
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logger.error(
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msg,
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exc_info=failure_to_exc_info(failure),
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extra={'spider': spider}
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)
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return errback
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dfd.addBoth(lambda _: self.downloader.close())
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dfd.addErrback(log_failure('Downloader close failure'))
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dfd.addBoth(lambda _: self.scraper.close_spider(spider))
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dfd.addErrback(log_failure('Scraper close failure'))
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dfd.addBoth(lambda _: slot.scheduler.close(reason))
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dfd.addErrback(log_failure('Scheduler close failure'))
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dfd.addBoth(lambda _: self.signals.send_catch_log_deferred(
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signal=signals.spider_closed, spider=spider, reason=reason))
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dfd.addErrback(log_failure('Error while sending spider_close signal'))
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dfd.addBoth(lambda _: self.crawler.stats.close_spider(spider, reason=reason))
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dfd.addErrback(log_failure('Stats close failure'))
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dfd.addBoth(lambda _: logger.info("Spider closed (%(reason)s)",
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{'reason': reason},
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extra={'spider': spider}))
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dfd.addBoth(lambda _: setattr(self, 'slot', None))
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dfd.addErrback(log_failure('Error while unassigning slot'))
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dfd.addBoth(lambda _: setattr(self, 'spider', None))
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dfd.addErrback(log_failure('Error while unassigning spider'))
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dfd.addBoth(lambda _: self._spider_closed_callback(spider))
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return dfd
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def _close_all_spiders(self):
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dfds = [self.close_spider(s, reason='shutdown') for s in self.open_spiders]
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dlist = defer.DeferredList(dfds)
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return dlist
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@defer.inlineCallbacks
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def _finish_stopping_engine(self):
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yield self.signals.send_catch_log_deferred(signal=signals.engine_stopped)
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self._closewait.callback(None)
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