mirror of https://github.com/scrapy/scrapy.git
394 lines
16 KiB
Python
394 lines
16 KiB
Python
"""
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This is the Scrapy engine which controls the Scheduler, Downloader and Spider.
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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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import warnings
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from time import time
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from typing import Callable, Iterable, Iterator, Optional, Set, Union
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from twisted.internet.defer import Deferred, inlineCallbacks, succeed
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from twisted.internet.task import LoopingCall
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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, ScrapyDeprecationWarning
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from scrapy.http import Response, Request
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from scrapy.spiders import Spider
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from scrapy.utils.log import logformatter_adapter, failure_to_exc_info
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from scrapy.utils.misc import create_instance, load_object
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from scrapy.utils.reactor import CallLaterOnce
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logger = logging.getLogger(__name__)
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class Slot:
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def __init__(
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self,
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start_requests: Iterable,
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close_if_idle: bool,
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nextcall: CallLaterOnce,
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scheduler,
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) -> None:
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self.closing: Optional[Deferred] = None
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self.inprogress: Set[Request] = set()
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self.start_requests: Optional[Iterator] = 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 = LoopingCall(nextcall.schedule)
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def add_request(self, request: Request) -> None:
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self.inprogress.add(request)
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def remove_request(self, request: Request) -> None:
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self.inprogress.remove(request)
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self._maybe_fire_closing()
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def close(self) -> Deferred:
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self.closing = 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) -> None:
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if self.closing is not None 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: Callable) -> None:
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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: Optional[Slot] = None
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self.spider: Optional[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(crawler.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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@inlineCallbacks
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def start(self) -> Deferred:
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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 = Deferred()
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yield self._closewait
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def stop(self) -> Deferred:
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"""Gracefully stop the execution engine"""
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@inlineCallbacks
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def _finish_stopping_engine(_) -> Deferred:
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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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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_spider(self.spider, reason="shutdown") if self.spider is not None else succeed(None)
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return dfd.addBoth(_finish_stopping_engine)
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def close(self) -> Deferred:
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"""
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Gracefully close the execution engine.
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If it has already been started, stop it. In all cases, close the spider and the downloader.
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"""
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if self.running:
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return self.stop() # will also close spider and downloader
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if self.spider is not None:
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return self.close_spider(self.spider, reason="shutdown") # will also close downloader
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return succeed(self.downloader.close())
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def pause(self) -> None:
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self.paused = True
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def unpause(self) -> None:
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self.paused = False
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def _next_request(self) -> None:
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assert self.slot is not None # typing
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assert self.spider is not None # typing
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if self.paused:
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return None
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while not self._needs_backout() and self._next_request_from_scheduler() is not None:
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pass
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if self.slot.start_requests is not None and not self._needs_backout():
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try:
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request = next(self.slot.start_requests)
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except StopIteration:
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self.slot.start_requests = None
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except Exception:
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self.slot.start_requests = None
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logger.error('Error while obtaining start requests', exc_info=True, extra={'spider': self.spider})
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else:
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self.crawl(request)
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if self.spider_is_idle() and self.slot.close_if_idle:
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self._spider_idle()
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def _needs_backout(self) -> bool:
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return (
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not self.running
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or self.slot.closing # type: ignore[union-attr]
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or self.downloader.needs_backout()
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or self.scraper.slot.needs_backout() # type: ignore[union-attr]
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)
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def _next_request_from_scheduler(self) -> Optional[Deferred]:
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assert self.slot is not None # typing
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assert self.spider is not None # typing
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request = self.slot.scheduler.next_request()
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if request is None:
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return None
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d = self._download(request, self.spider)
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d.addBoth(self._handle_downloader_output, request)
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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': self.spider}))
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d.addBoth(lambda _: self.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': self.spider}))
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d.addBoth(lambda _: self.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': self.spider}))
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return d
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def _handle_downloader_output(
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self, result: Union[Request, Response, Failure], request: Request
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) -> Optional[Deferred]:
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assert self.spider is not None # typing
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if not isinstance(result, (Request, Response, Failure)):
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raise TypeError(f"Incorrect type: expected Request, Response or Failure, got {type(result)}: {result!r}")
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# downloader middleware can return requests (for example, redirects)
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if isinstance(result, Request):
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self.crawl(result)
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return None
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d = self.scraper.enqueue_scrape(result, request, self.spider)
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d.addErrback(
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lambda f: logger.error(
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"Error while enqueuing downloader output",
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exc_info=failure_to_exc_info(f),
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extra={'spider': self.spider},
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)
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)
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return d
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def spider_is_idle(self, spider: Optional[Spider] = None) -> bool:
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if spider is not None:
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warnings.warn(
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"Passing a 'spider' argument to ExecutionEngine.spider_is_idle is deprecated",
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category=ScrapyDeprecationWarning,
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stacklevel=2,
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)
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if self.slot is None:
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raise RuntimeError("Engine slot not assigned")
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if not self.scraper.slot.is_idle(): # type: ignore[union-attr]
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return False
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if self.downloader.active: # downloader has pending requests
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return False
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if self.slot.start_requests is not None: # 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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return False
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return True
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def crawl(self, request: Request, spider: Optional[Spider] = None) -> None:
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"""Inject the request into the spider <-> downloader pipeline"""
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if spider is not None:
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warnings.warn(
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"Passing a 'spider' argument to ExecutionEngine.crawl is deprecated",
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category=ScrapyDeprecationWarning,
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stacklevel=2,
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)
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if spider is not self.spider:
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raise RuntimeError(f"The spider {spider.name!r} does not match the open spider")
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if self.spider is None:
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raise RuntimeError(f"No open spider to crawl: {request}")
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self._schedule_request(request, self.spider)
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self.slot.nextcall.schedule() # type: ignore[union-attr]
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def _schedule_request(self, request: Request, spider: Spider) -> None:
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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): # type: ignore[union-attr]
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self.signals.send_catch_log(signals.request_dropped, request=request, spider=spider)
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def download(self, request: Request, spider: Optional[Spider] = None) -> Deferred:
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"""Return a Deferred which fires with a Response as result, only downloader middlewares are applied"""
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if spider is None:
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spider = self.spider
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else:
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warnings.warn(
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"Passing a 'spider' argument to ExecutionEngine.download is deprecated",
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category=ScrapyDeprecationWarning,
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stacklevel=2,
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)
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if spider is not self.spider:
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logger.warning("The spider '%s' does not match the open spider", spider.name)
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if spider is None:
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raise RuntimeError(f"No open spider to crawl: {request}")
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return self._download(request, spider).addBoth(self._downloaded, request, spider)
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def _downloaded(
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self, result: Union[Response, Request], request: Request, spider: Spider
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) -> Union[Deferred, Response]:
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assert self.slot is not None # typing
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self.slot.remove_request(request)
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return self.download(result, spider) if isinstance(result, Request) else result
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def _download(self, request: Request, spider: Spider) -> Deferred:
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assert self.slot is not None # typing
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self.slot.add_request(request)
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def _on_success(result: Union[Response, Request]) -> Union[Response, Request]:
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if not isinstance(result, (Response, Request)):
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raise TypeError(f"Incorrect type: expected Response or Request, got {type(result)}: {result!r}")
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if isinstance(result, Response):
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if result.request is None:
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result.request = request
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logkws = self.logformatter.crawled(result.request, result, 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=result,
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request=result.request,
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spider=spider,
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)
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return result
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def _on_complete(_):
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self.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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@inlineCallbacks
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def open_spider(self, spider: Spider, start_requests: Iterable = (), close_if_idle: bool = True):
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if self.slot is not None:
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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)
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scheduler = create_instance(self.scheduler_cls, settings=None, crawler=self.crawler)
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start_requests = yield self.scraper.spidermw.process_start_requests(start_requests, spider)
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self.slot = Slot(start_requests, close_if_idle, nextcall, scheduler)
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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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self.slot.nextcall.schedule()
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self.slot.heartbeat.start(5)
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def _spider_idle(self) -> None:
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"""
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Called when a spider gets idle, i.e. when there are no remaining requests to download or schedule.
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It can be called multiple times. If a handler for the spider_idle signal raises a DontCloseSpider
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exception, the spider is not closed until the next loop and this function is guaranteed to be called
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(at least) once again.
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"""
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assert self.spider is not None # typing
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res = self.signals.send_catch_log(signals.spider_idle, spider=self.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 None
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if self.spider_is_idle():
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self.close_spider(self.spider, reason='finished')
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def close_spider(self, spider: Spider, reason: str = "cancelled") -> Deferred:
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"""Close (cancel) spider and clear all its outstanding requests"""
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if self.slot is None:
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raise RuntimeError("Engine slot not assigned")
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if self.slot.closing is not None:
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return self.slot.closing
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logger.info("Closing spider (%(reason)s)", {'reason': reason}, extra={'spider': spider})
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dfd = self.slot.close()
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def log_failure(msg: str) -> Callable:
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def errback(failure: Failure) -> None:
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logger.error(msg, exc_info=failure_to_exc_info(failure), extra={'spider': spider})
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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 _: self.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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))
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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)", {'reason': reason}, 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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@property
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def open_spiders(self) -> list:
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warnings.warn(
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"ExecutionEngine.open_spiders is deprecated, please use ExecutionEngine.spider instead",
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category=ScrapyDeprecationWarning,
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stacklevel=2,
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)
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return [self.spider] if self.spider is not None else []
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def has_capacity(self) -> bool:
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warnings.warn("ExecutionEngine.has_capacity is deprecated", ScrapyDeprecationWarning, stacklevel=2)
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return not bool(self.slot)
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def schedule(self, request: Request, spider: Spider) -> None:
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warnings.warn(
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"ExecutionEngine.schedule is deprecated, please use "
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"ExecutionEngine.crawl or ExecutionEngine.download instead",
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category=ScrapyDeprecationWarning,
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stacklevel=2,
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)
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if self.slot is None:
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raise RuntimeError("Engine slot not assigned")
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self._schedule_request(request, spider)
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