Source code for scrapy.crawler

import logging
import pprint
import signal
import warnings

from twisted.internet import defer
from zope.interface.verify import DoesNotImplement, verifyClass

from scrapy import signals, Spider
from scrapy.core.engine import ExecutionEngine
from scrapy.exceptions import ScrapyDeprecationWarning
from scrapy.extension import ExtensionManager
from scrapy.interfaces import ISpiderLoader
from scrapy.settings import overridden_settings, Settings
from scrapy.signalmanager import SignalManager
from scrapy.utils.log import (
    configure_logging,
    get_scrapy_root_handler,
    install_scrapy_root_handler,
    log_scrapy_info,
    LogCounterHandler,
)
from scrapy.utils.misc import create_instance, load_object
from scrapy.utils.ossignal import install_shutdown_handlers, signal_names
from scrapy.utils.reactor import install_reactor, verify_installed_reactor


logger = logging.getLogger(__name__)


[docs]class Crawler: def __init__(self, spidercls, settings=None): if isinstance(spidercls, Spider): raise ValueError('The spidercls argument must be a class, not an object') if isinstance(settings, dict) or settings is None: settings = Settings(settings) self.spidercls = spidercls self.settings = settings.copy() self.spidercls.update_settings(self.settings) self.signals = SignalManager(self) self.stats = load_object(self.settings['STATS_CLASS'])(self) handler = LogCounterHandler(self, level=self.settings.get('LOG_LEVEL')) logging.root.addHandler(handler) d = dict(overridden_settings(self.settings)) logger.info("Overridden settings:\n%(settings)s", {'settings': pprint.pformat(d)}) if get_scrapy_root_handler() is not None: # scrapy root handler already installed: update it with new settings install_scrapy_root_handler(self.settings) # lambda is assigned to Crawler attribute because this way it is not # garbage collected after leaving __init__ scope self.__remove_handler = lambda: logging.root.removeHandler(handler) self.signals.connect(self.__remove_handler, signals.engine_stopped) lf_cls = load_object(self.settings['LOG_FORMATTER']) self.logformatter = lf_cls.from_crawler(self) self.extensions = ExtensionManager.from_crawler(self) self.settings.freeze() self.crawling = False self.spider = None self.engine = None @property def spiders(self): if not hasattr(self, '_spiders'): warnings.warn("Crawler.spiders is deprecated, use " "CrawlerRunner.spider_loader or instantiate " "scrapy.spiderloader.SpiderLoader with your " "settings.", category=ScrapyDeprecationWarning, stacklevel=2) self._spiders = _get_spider_loader(self.settings.frozencopy()) return self._spiders
[docs] @defer.inlineCallbacks def crawl(self, *args, **kwargs): assert not self.crawling, "Crawling already taking place" self.crawling = True try: self.spider = self._create_spider(*args, **kwargs) self.engine = self._create_engine() start_requests = iter(self.spider.start_requests()) yield self.engine.open_spider(self.spider, start_requests) yield defer.maybeDeferred(self.engine.start) except Exception: self.crawling = False if self.engine is not None: yield self.engine.close() raise
def _create_spider(self, *args, **kwargs): return self.spidercls.from_crawler(self, *args, **kwargs) def _create_engine(self): return ExecutionEngine(self, lambda _: self.stop())
[docs] @defer.inlineCallbacks def stop(self): """Starts a graceful stop of the crawler and returns a deferred that is fired when the crawler is stopped.""" if self.crawling: self.crawling = False yield defer.maybeDeferred(self.engine.stop)
[docs]class CrawlerRunner: """ This is a convenient helper class that keeps track of, manages and runs crawlers inside an already setup :mod:`~twisted.internet.reactor`. The CrawlerRunner object must be instantiated with a :class:`~scrapy.settings.Settings` object. This class shouldn't be needed (since Scrapy is responsible of using it accordingly) unless writing scripts that manually handle the crawling process. See :ref:`run-from-script` for an example. """ crawlers = property( lambda self: self._crawlers, doc="Set of :class:`crawlers <scrapy.crawler.Crawler>` started by " ":meth:`crawl` and managed by this class." ) def __init__(self, settings=None): if isinstance(settings, dict) or settings is None: settings = Settings(settings) self.settings = settings self.spider_loader = _get_spider_loader(settings) self._crawlers = set() self._active = set() self.bootstrap_failed = False self._handle_twisted_reactor() @property def spiders(self): warnings.warn("CrawlerRunner.spiders attribute is renamed to " "CrawlerRunner.spider_loader.", category=ScrapyDeprecationWarning, stacklevel=2) return self.spider_loader
[docs] def crawl(self, crawler_or_spidercls, *args, **kwargs): """ Run a crawler with the provided arguments. It will call the given Crawler's :meth:`~Crawler.crawl` method, while keeping track of it so it can be stopped later. If ``crawler_or_spidercls`` isn't a :class:`~scrapy.crawler.Crawler` instance, this method will try to create one using this parameter as the spider class given to it. Returns a deferred that is fired when the crawling is finished. :param crawler_or_spidercls: already created crawler, or a spider class or spider's name inside the project to create it :type crawler_or_spidercls: :class:`~scrapy.crawler.Crawler` instance, :class:`~scrapy.spiders.Spider` subclass or string :param list args: arguments to initialize the spider :param dict kwargs: keyword arguments to initialize the spider """ if isinstance(crawler_or_spidercls, Spider): raise ValueError( 'The crawler_or_spidercls argument cannot be a spider object, ' 'it must be a spider class (or a Crawler object)') crawler = self.create_crawler(crawler_or_spidercls) return self._crawl(crawler, *args, **kwargs)
def _crawl(self, crawler, *args, **kwargs): self.crawlers.add(crawler) d = crawler.crawl(*args, **kwargs) self._active.add(d) def _done(result): self.crawlers.discard(crawler) self._active.discard(d) self.bootstrap_failed |= not getattr(crawler, 'spider', None) return result return d.addBoth(_done)
[docs] def create_crawler(self, crawler_or_spidercls): """ Return a :class:`~scrapy.crawler.Crawler` object. * If ``crawler_or_spidercls`` is a Crawler, it is returned as-is. * If ``crawler_or_spidercls`` is a Spider subclass, a new Crawler is constructed for it. * If ``crawler_or_spidercls`` is a string, this function finds a spider with this name in a Scrapy project (using spider loader), then creates a Crawler instance for it. """ if isinstance(crawler_or_spidercls, Spider): raise ValueError( 'The crawler_or_spidercls argument cannot be a spider object, ' 'it must be a spider class (or a Crawler object)') if isinstance(crawler_or_spidercls, Crawler): return crawler_or_spidercls return self._create_crawler(crawler_or_spidercls)
def _create_crawler(self, spidercls): if isinstance(spidercls, str): spidercls = self.spider_loader.load(spidercls) return Crawler(spidercls, self.settings)
[docs] def stop(self): """ Stops simultaneously all the crawling jobs taking place. Returns a deferred that is fired when they all have ended. """ return defer.DeferredList([c.stop() for c in list(self.crawlers)])
[docs] @defer.inlineCallbacks def join(self): """ join() Returns a deferred that is fired when all managed :attr:`crawlers` have completed their executions. """ while self._active: yield defer.DeferredList(self._active)
def _handle_twisted_reactor(self): if self.settings.get("TWISTED_REACTOR"): verify_installed_reactor(self.settings["TWISTED_REACTOR"])
[docs]class CrawlerProcess(CrawlerRunner): """ A class to run multiple scrapy crawlers in a process simultaneously. This class extends :class:`~scrapy.crawler.CrawlerRunner` by adding support for starting a :mod:`~twisted.internet.reactor` and handling shutdown signals, like the keyboard interrupt command Ctrl-C. It also configures top-level logging. This utility should be a better fit than :class:`~scrapy.crawler.CrawlerRunner` if you aren't running another :mod:`~twisted.internet.reactor` within your application. The CrawlerProcess object must be instantiated with a :class:`~scrapy.settings.Settings` object. :param install_root_handler: whether to install root logging handler (default: True) This class shouldn't be needed (since Scrapy is responsible of using it accordingly) unless writing scripts that manually handle the crawling process. See :ref:`run-from-script` for an example. """ def __init__(self, settings=None, install_root_handler=True): super(CrawlerProcess, self).__init__(settings) install_shutdown_handlers(self._signal_shutdown) configure_logging(self.settings, install_root_handler) log_scrapy_info(self.settings) def _signal_shutdown(self, signum, _): from twisted.internet import reactor install_shutdown_handlers(self._signal_kill) signame = signal_names[signum] logger.info("Received %(signame)s, shutting down gracefully. Send again to force ", {'signame': signame}) reactor.callFromThread(self._graceful_stop_reactor) def _signal_kill(self, signum, _): from twisted.internet import reactor install_shutdown_handlers(signal.SIG_IGN) signame = signal_names[signum] logger.info('Received %(signame)s twice, forcing unclean shutdown', {'signame': signame}) reactor.callFromThread(self._stop_reactor)
[docs] def start(self, stop_after_crawl=True): """ This method starts a :mod:`~twisted.internet.reactor`, adjusts its pool size to :setting:`REACTOR_THREADPOOL_MAXSIZE`, and installs a DNS cache based on :setting:`DNSCACHE_ENABLED` and :setting:`DNSCACHE_SIZE`. If ``stop_after_crawl`` is True, the reactor will be stopped after all crawlers have finished, using :meth:`join`. :param boolean stop_after_crawl: stop or not the reactor when all crawlers have finished """ from twisted.internet import reactor if stop_after_crawl: d = self.join() # Don't start the reactor if the deferreds are already fired if d.called: return d.addBoth(self._stop_reactor) resolver_class = load_object(self.settings["DNS_RESOLVER"]) resolver = create_instance(resolver_class, self.settings, self, reactor=reactor) resolver.install_on_reactor() tp = reactor.getThreadPool() tp.adjustPoolsize(maxthreads=self.settings.getint('REACTOR_THREADPOOL_MAXSIZE')) reactor.addSystemEventTrigger('before', 'shutdown', self.stop) reactor.run(installSignalHandlers=False) # blocking call
def _graceful_stop_reactor(self): d = self.stop() d.addBoth(self._stop_reactor) return d def _stop_reactor(self, _=None): from twisted.internet import reactor try: reactor.stop() except RuntimeError: # raised if already stopped or in shutdown stage pass def _handle_twisted_reactor(self): if self.settings.get("TWISTED_REACTOR"): install_reactor(self.settings["TWISTED_REACTOR"]) super()._handle_twisted_reactor()
def _get_spider_loader(settings): """ Get SpiderLoader instance from settings """ cls_path = settings.get('SPIDER_LOADER_CLASS') loader_cls = load_object(cls_path) try: verifyClass(ISpiderLoader, loader_cls) except DoesNotImplement: warnings.warn( 'SPIDER_LOADER_CLASS (previously named SPIDER_MANAGER_CLASS) does ' 'not fully implement scrapy.interfaces.ISpiderLoader interface. ' 'Please add all missing methods to avoid unexpected runtime errors.', category=ScrapyDeprecationWarning, stacklevel=2 ) return loader_cls.from_settings(settings.frozencopy())