mirror of https://github.com/scrapy/scrapy.git
547 lines
20 KiB
Python
547 lines
20 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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from __future__ import annotations
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import asyncio
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import logging
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from time import time
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from traceback import format_exc
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from typing import TYPE_CHECKING, Any, cast
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from twisted.internet.defer import CancelledError, Deferred, inlineCallbacks, succeed
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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.scheduler import BaseScheduler
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from scrapy.core.scraper import Scraper
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from scrapy.exceptions import CloseSpider, DontCloseSpider, IgnoreRequest
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from scrapy.http import Request, Response
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from scrapy.utils.asyncio import AsyncioLoopingCall, create_looping_call
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from scrapy.utils.defer import (
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deferred_f_from_coro_f,
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deferred_from_coro,
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maybe_deferred_to_future,
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)
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from scrapy.utils.log import failure_to_exc_info, logformatter_adapter
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from scrapy.utils.misc import build_from_crawler, load_object
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from scrapy.utils.reactor import CallLaterOnce
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if TYPE_CHECKING:
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from collections.abc import AsyncIterator, Callable, Generator
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from twisted.internet.task import LoopingCall
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from scrapy.core.downloader import Downloader
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from scrapy.crawler import Crawler
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from scrapy.logformatter import LogFormatter
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from scrapy.settings import BaseSettings, Settings
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from scrapy.signalmanager import SignalManager
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from scrapy.spiders import Spider
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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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close_if_idle: bool,
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nextcall: CallLaterOnce[None],
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scheduler: BaseScheduler,
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) -> None:
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self.closing: Deferred[None] | None = None
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self.inprogress: set[Request] = set()
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self.close_if_idle: bool = close_if_idle
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self.nextcall: CallLaterOnce[None] = nextcall
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self.scheduler: BaseScheduler = scheduler
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self.heartbeat: AsyncioLoopingCall | LoopingCall = create_looping_call(
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nextcall.schedule
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)
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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[None]:
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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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_SLOT_HEARTBEAT_INTERVAL: float = 5.0
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def __init__(
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self,
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crawler: Crawler,
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spider_closed_callback: Callable[[Spider], Deferred[None] | None],
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) -> None:
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self.crawler: Crawler = crawler
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self.settings: Settings = crawler.settings
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self.signals: SignalManager = crawler.signals
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assert crawler.logformatter
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self.logformatter: LogFormatter = crawler.logformatter
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self._slot: _Slot | None = None
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self.spider: Spider | None = None
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self.running: bool = False
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self.paused: bool = False
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self._spider_closed_callback: Callable[[Spider], Deferred[None] | None] = (
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spider_closed_callback
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)
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self.start_time: float | None = None
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self._start: AsyncIterator[Any] | None = None
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self._closewait: Deferred[None] | None = None
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self._start_request_processing_dfd: Deferred[None] | None = None
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downloader_cls: type[Downloader] = load_object(self.settings["DOWNLOADER"])
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try:
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self.scheduler_cls: type[BaseScheduler] = self._get_scheduler_class(
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crawler.settings
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)
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self.downloader: Downloader = downloader_cls(crawler)
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self.scraper: Scraper = Scraper(crawler)
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except Exception:
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self.close()
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raise
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def _get_scheduler_class(self, settings: BaseSettings) -> type[BaseScheduler]:
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scheduler_cls: type[BaseScheduler] = load_object(settings["SCHEDULER"])
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if not issubclass(scheduler_cls, BaseScheduler):
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raise TypeError(
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f"The provided scheduler class ({settings['SCHEDULER']})"
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" does not fully implement the scheduler interface"
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)
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return scheduler_cls
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def start(self, _start_request_processing=True) -> Deferred[None]:
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return deferred_from_coro(self.start_async(_start_request_processing))
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async def start_async(self, _start_request_processing=True) -> None:
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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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await self.signals.send_catch_log_async(signal=signals.engine_started)
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if _start_request_processing and self.spider is None:
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# require an opened spider when not run in scrapy shell
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return
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self.running = True
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self._closewait = Deferred()
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if _start_request_processing:
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self._start_request_processing_dfd = self._start_request_processing()
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await maybe_deferred_to_future(self._closewait)
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def stop(self) -> Deferred[None]:
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"""Gracefully stop the execution engine"""
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@deferred_f_from_coro_f
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async def _finish_stopping_engine(_: Any) -> None:
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await self.signals.send_catch_log_async(signal=signals.engine_stopped)
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if self._closewait:
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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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if self._start_request_processing_dfd is not None:
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self._start_request_processing_dfd.cancel()
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self._start_request_processing_dfd = None
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dfd = (
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self.close_spider(self.spider, reason="shutdown")
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if self.spider is not None
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else succeed(None)
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)
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return dfd.addBoth(_finish_stopping_engine)
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def close(self) -> Deferred[None]:
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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(
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self.spider, reason="shutdown"
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) # will also close downloader
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if hasattr(self, "downloader"):
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self.downloader.close()
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return succeed(None)
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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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async def _process_start_next(self):
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"""Processes the next item or request from Spider.start().
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If a request, it is scheduled. If an item, it is sent to item
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pipelines.
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"""
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try:
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item_or_request = await self._start.__anext__()
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except StopAsyncIteration:
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self._start = None
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except Exception as exception:
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self._start = None
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exception_traceback = format_exc()
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logger.error(
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f"Error while reading start items and requests: {exception}.\n{exception_traceback}",
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exc_info=True,
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)
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else:
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if not self.spider:
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return # spider already closed
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if isinstance(item_or_request, Request):
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self.crawl(item_or_request)
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else:
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self.scraper.start_itemproc(item_or_request, response=None)
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self._slot.nextcall.schedule()
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@deferred_f_from_coro_f
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async def _start_request_processing(self) -> None:
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"""Starts consuming Spider.start() output and sending scheduled
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requests."""
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# Starts the processing of scheduled requests, as well as a periodic
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# call to that processing method for scenarios where the scheduler
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# reports having pending requests but returns none.
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try:
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assert self._slot is not None # typing
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self._slot.nextcall.schedule()
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self._slot.heartbeat.start(self._SLOT_HEARTBEAT_INTERVAL)
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while self._start and self.spider:
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await self._process_start_next()
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if not self.needs_backout():
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# Give room for the outcome of self._process_start_next() to be
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# processed before continuing with the next iteration.
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self._slot.nextcall.schedule()
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await self._slot.nextcall.wait()
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except (asyncio.exceptions.CancelledError, CancelledError):
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# self.stop() has cancelled us, nothing to do
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return
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except Exception:
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# an error happened, log it and stop the engine
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self._start_request_processing_dfd = None
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logger.error(
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"Error while processing requests from start()",
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exc_info=True,
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extra={"spider": self.spider},
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)
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await maybe_deferred_to_future(self.stop())
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def _start_scheduled_requests(self) -> None:
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if self._slot is None or self._slot.closing is not None or self.paused:
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return
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while not self.needs_backout():
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if not self._start_scheduled_request():
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break
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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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"""Returns ``True`` if no more requests can be sent at the moment, or
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``False`` otherwise.
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See :ref:`start-requests-lazy` for an example.
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"""
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assert self.scraper.slot is not None # typing
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return (
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not self.running
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or not self._slot
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or bool(self._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 _start_scheduled_request(self) -> bool:
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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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self.signals.send_catch_log(signals.scheduler_empty)
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return False
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d: Deferred[Response | Request] = self._download(request)
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d.addBoth(self._handle_downloader_output, request)
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d.addErrback(
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lambda f: logger.info(
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"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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)
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)
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def _remove_request(_: Any) -> None:
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assert self._slot
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self._slot.remove_request(request)
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d2: Deferred[None] = d.addBoth(_remove_request)
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d2.addErrback(
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lambda f: logger.info(
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"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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)
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)
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slot = self._slot
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d2.addBoth(lambda _: slot.nextcall.schedule())
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d2.addErrback(
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lambda f: logger.info(
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"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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)
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)
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return True
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@inlineCallbacks
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def _handle_downloader_output(
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self, result: Request | Response | Failure, request: Request
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) -> Generator[Deferred[Any], Any, None]:
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if not isinstance(result, (Request, Response, Failure)):
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raise TypeError(
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f"Incorrect type: expected Request, Response or Failure, got {type(result)}: {result!r}"
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)
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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
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try:
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yield self.scraper.enqueue_scrape(result, request)
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except Exception:
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assert self.spider is not None
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logger.error(
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"Error while enqueuing scrape",
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exc_info=True,
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extra={"spider": self.spider},
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)
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def spider_is_idle(self) -> bool:
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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._start is not None: # not all start requests are handled
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return False
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return not self._slot.scheduler.has_pending_requests()
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def crawl(self, request: Request) -> None:
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"""Inject the request into the spider <-> downloader pipeline"""
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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)
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self._slot.nextcall.schedule() # type: ignore[union-attr]
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def _schedule_request(self, request: Request) -> None:
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request_scheduled_result = self.signals.send_catch_log(
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signals.request_scheduled,
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request=request,
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spider=self.spider,
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dont_log=IgnoreRequest,
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)
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for handler, result in request_scheduled_result:
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if isinstance(result, Failure) and isinstance(result.value, IgnoreRequest):
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return
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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(
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signals.request_dropped, request=request, spider=self.spider
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)
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@inlineCallbacks
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def download(self, request: Request) -> Generator[Deferred[Any], Any, Response]:
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"""Return a Deferred which fires with a Response as result, only downloader middlewares are applied"""
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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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try:
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response_or_request = yield self._download(request)
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finally:
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assert self._slot is not None
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self._slot.remove_request(request)
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if isinstance(response_or_request, Request):
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return (yield self.download(response_or_request))
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return response_or_request
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@inlineCallbacks
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def _download(
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self, request: Request
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) -> Generator[Deferred[Any], Any, Response | Request]:
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assert self._slot is not None # typing
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assert self.spider is not None
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self._slot.add_request(request)
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try:
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result: Response | Request = yield self.downloader.fetch(
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request, self.spider
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)
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if not isinstance(result, (Response, Request)):
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raise TypeError(
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f"Incorrect type: expected Response or Request, got {type(result)}: {result!r}"
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)
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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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assert self.spider is not None
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logkws = self.logformatter.crawled(result.request, result, self.spider)
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if logkws is not None:
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logger.log(
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*logformatter_adapter(logkws), extra={"spider": self.spider}
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)
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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=self.spider,
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)
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return result
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finally:
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self._slot.nextcall.schedule()
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def open_spider(self, spider: Spider, close_if_idle: bool = True) -> Deferred[None]:
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return deferred_from_coro(
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self.open_spider_async(spider, close_if_idle=close_if_idle)
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)
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async def open_spider_async(
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self,
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spider: Spider,
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*,
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close_if_idle: bool = True,
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) -> None:
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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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self.spider = spider
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nextcall = CallLaterOnce(self._start_scheduled_requests)
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scheduler = build_from_crawler(self.scheduler_cls, self.crawler)
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self._slot = _Slot(close_if_idle, nextcall, scheduler)
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self._start = await self.scraper.spidermw.process_start(spider)
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if hasattr(scheduler, "open") and (d := scheduler.open(spider)):
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await maybe_deferred_to_future(d)
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await maybe_deferred_to_future(self.scraper.open_spider(spider))
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assert self.crawler.stats
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self.crawler.stats.open_spider(spider)
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await self.signals.send_catch_log_async(signals.spider_opened, spider=spider)
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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. A handler can raise CloseSpider to provide a custom closing reason.
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"""
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assert self.spider is not None # typing
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expected_ex = (DontCloseSpider, CloseSpider)
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res = self.signals.send_catch_log(
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signals.spider_idle, spider=self.spider, dont_log=expected_ex
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)
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detected_ex = {
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ex: x.value
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for _, x in res
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for ex in expected_ex
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if isinstance(x, Failure) and isinstance(x.value, ex)
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}
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if DontCloseSpider in detected_ex:
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return
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if self.spider_is_idle():
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ex = detected_ex.get(CloseSpider, CloseSpider(reason="finished"))
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assert isinstance(ex, CloseSpider) # typing
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self.close_spider(self.spider, reason=ex.reason)
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def close_spider(self, spider: Spider, reason: str = "cancelled") -> Deferred[None]:
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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(
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"Closing spider (%(reason)s)", {"reason": reason}, extra={"spider": spider}
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)
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dfd = self._slot.close()
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def log_failure(msg: str) -> Callable[[Failure], None]:
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def errback(failure: Failure) -> None:
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logger.error(
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msg, exc_info=failure_to_exc_info(failure), 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"))
|
|
|
|
dfd.addBoth(lambda _: self.scraper.close_spider())
|
|
dfd.addErrback(log_failure("Scraper close failure"))
|
|
|
|
if hasattr(self._slot.scheduler, "close"):
|
|
dfd.addBoth(lambda _: cast("_Slot", self._slot).scheduler.close(reason))
|
|
dfd.addErrback(log_failure("Scheduler close failure"))
|
|
|
|
dfd.addBoth(
|
|
lambda _: self.signals.send_catch_log_deferred(
|
|
signal=signals.spider_closed,
|
|
spider=spider,
|
|
reason=reason,
|
|
)
|
|
)
|
|
dfd.addErrback(log_failure("Error while sending spider_close signal"))
|
|
|
|
def close_stats(_: Any) -> None:
|
|
assert self.crawler.stats
|
|
self.crawler.stats.close_spider(spider, reason=reason)
|
|
|
|
dfd.addBoth(close_stats)
|
|
dfd.addErrback(log_failure("Stats close failure"))
|
|
|
|
dfd.addBoth(
|
|
lambda _: logger.info(
|
|
"Spider closed (%(reason)s)",
|
|
{"reason": reason},
|
|
extra={"spider": spider},
|
|
)
|
|
)
|
|
|
|
def unassign_slot(_: Any) -> None:
|
|
self._slot = None
|
|
|
|
dfd.addBoth(unassign_slot)
|
|
dfd.addErrback(log_failure("Error while unassigning slot"))
|
|
|
|
def unassign_spider(_: Any) -> None:
|
|
self.spider = None
|
|
|
|
dfd.addBoth(unassign_spider)
|
|
dfd.addErrback(log_failure("Error while unassigning spider"))
|
|
|
|
dfd.addBoth(lambda _: self._spider_closed_callback(spider))
|
|
dfd.addErrback(log_failure("Error running spider_closed_callback"))
|
|
|
|
return dfd
|