scrapy框架之自定制命令

  1 import six
  2 import signal
  3 import logging
  4 import warnings
  5 
  6 import sys
  7 from twisted.internet import reactor, defer
  8 from zope.interface.verify import verifyClass, DoesNotImplement
  9 
 10 from scrapy.core.engine import ExecutionEngine
 11 from scrapy.resolver import CachingThreadedResolver
 12 from scrapy.interfaces import ISpiderLoader
 13 from scrapy.extension import ExtensionManager
 14 from scrapy.settings import overridden_settings, Settings
 15 from scrapy.signalmanager import SignalManager
 16 from scrapy.exceptions import ScrapyDeprecationWarning
 17 from scrapy.utils.ossignal import install_shutdown_handlers, signal_names
 18 from scrapy.utils.misc import load_object
 19 from scrapy.utils.log import (
 20     LogCounterHandler, configure_logging, log_scrapy_info,
 21     get_scrapy_root_handler, install_scrapy_root_handler)
 22 from scrapy import signals
 23 
 24 logger = logging.getLogger(__name__)
 25 
 26 
 27 class Crawler(object):
 28 
 29     def __init__(self, spidercls, settings=None):
 30         if isinstance(settings, dict) or settings is None:
 31             settings = Settings(settings)
 32 
 33         self.spidercls = spidercls
 34         self.settings = settings.copy()
 35         self.spidercls.update_settings(self.settings)
 36 
 37         d = dict(overridden_settings(self.settings))
 38         logger.info("Overridden settings: %(settings)r", {'settings': d})
 39 
 40         self.signals = SignalManager(self)
 41         self.stats = load_object(self.settings['STATS_CLASS'])(self)
 42 
 43         handler = LogCounterHandler(self, level=self.settings.get('LOG_LEVEL'))
 44         logging.root.addHandler(handler)
 45         if get_scrapy_root_handler() is not None:
 46             # scrapy root handler already installed: update it with new settings
 47             install_scrapy_root_handler(self.settings)
 48         # lambda is assigned to Crawler attribute because this way it is not
 49         # garbage collected after leaving __init__ scope
 50         self.__remove_handler = lambda: logging.root.removeHandler(handler)
 51         self.signals.connect(self.__remove_handler, signals.engine_stopped)
 52 
 53         lf_cls = load_object(self.settings['LOG_FORMATTER'])
 54         self.logformatter = lf_cls.from_crawler(self)
 55         self.extensions = ExtensionManager.from_crawler(self)
 56 
 57         self.settings.freeze()
 58         self.crawling = False
 59         self.spider = None
 60         self.engine = None
 61 
 62     @property
 63     def spiders(self):
 64         if not hasattr(self, '_spiders'):
 65             warnings.warn("Crawler.spiders is deprecated, use "
 66                           "CrawlerRunner.spider_loader or instantiate "
 67                           "scrapy.spiderloader.SpiderLoader with your "
 68                           "settings.",
 69                           category=ScrapyDeprecationWarning, stacklevel=2)
 70             self._spiders = _get_spider_loader(self.settings.frozencopy())
 71         return self._spiders
 72 
 73     @defer.inlineCallbacks
 74     def crawl(self, *args, **kwargs):
 75         assert not self.crawling, "Crawling already taking place"
 76         self.crawling = True
 77 
 78         try:
 79             self.spider = self._create_spider(*args, **kwargs)
 80             self.engine = self._create_engine()
 81             start_requests = iter(self.spider.start_requests())
 82             yield self.engine.open_spider(self.spider, start_requests)
 83             yield defer.maybeDeferred(self.engine.start)
 84         except Exception:
 85             # In Python 2 reraising an exception after yield discards
 86             # the original traceback (see https://bugs.python.org/issue7563),
 87             # so sys.exc_info() workaround is used.
 88             # This workaround also works in Python 3, but it is not needed,
 89             # and it is slower, so in Python 3 we use native `raise`.
 90             if six.PY2:
 91                 exc_info = sys.exc_info()
 92 
 93             self.crawling = False
 94             if self.engine is not None:
 95                 yield self.engine.close()
 96 
 97             if six.PY2:
 98                 six.reraise(*exc_info)
 99             raise
100 
101     def _create_spider(self, *args, **kwargs):
102         return self.spidercls.from_crawler(self, *args, **kwargs)
103 
104     def _create_engine(self):
105         return ExecutionEngine(self, lambda _: self.stop())
106 
107     @defer.inlineCallbacks
108     def stop(self):
109         if self.crawling:
110             self.crawling = False
111             yield defer.maybeDeferred(self.engine.stop)
112 
113 
114 class CrawlerRunner(object):
115     """
116     This is a convenient helper class that keeps track of, manages and runs
117     crawlers inside an already setup Twisted `reactor`_.
118 
119     The CrawlerRunner object must be instantiated with a
120     :class:`~scrapy.settings.Settings` object.
121 
122     This class shouldn't be needed (since Scrapy is responsible of using it
123     accordingly) unless writing scripts that manually handle the crawling
124     process. See :ref:`run-from-script` for an example.
125     """
126 
127     crawlers = property(
128         lambda self: self._crawlers,
129         doc="Set of :class:`crawlers <scrapy.crawler.Crawler>` started by "
130             ":meth:`crawl` and managed by this class."
131     )
132 
133     def __init__(self, settings=None):
134         if isinstance(settings, dict) or settings is None:
135             settings = Settings(settings)
136         self.settings = settings
137         self.spider_loader = _get_spider_loader(settings)
138         self._crawlers = set()
139         self._active = set()
140 
141     @property
142     def spiders(self):
143         warnings.warn("CrawlerRunner.spiders attribute is renamed to "
144                       "CrawlerRunner.spider_loader.",
145                       category=ScrapyDeprecationWarning, stacklevel=2)
146         return self.spider_loader
147 
148     def crawl(self, crawler_or_spidercls, *args, **kwargs):
149         """
150         Run a crawler with the provided arguments.
151 
152         It will call the given Crawler's :meth:`~Crawler.crawl` method, while
153         keeping track of it so it can be stopped later.
154 
155         If `crawler_or_spidercls` isn't a :class:`~scrapy.crawler.Crawler`
156         instance, this method will try to create one using this parameter as
157         the spider class given to it.
158 
159         Returns a deferred that is fired when the crawling is finished.
160 
161         :param crawler_or_spidercls: already created crawler, or a spider class
162             or spider's name inside the project to create it
163         :type crawler_or_spidercls: :class:`~scrapy.crawler.Crawler` instance,
164             :class:`~scrapy.spiders.Spider` subclass or string
165 
166         :param list args: arguments to initialize the spider
167 
168         :param dict kwargs: keyword arguments to initialize the spider
169         """
170         crawler = self.create_crawler(crawler_or_spidercls)
171         return self._crawl(crawler, *args, **kwargs)
172 
173     def _crawl(self, crawler, *args, **kwargs):
174         self.crawlers.add(crawler)
175         d = crawler.crawl(*args, **kwargs)
176         self._active.add(d)
177 
178         def _done(result):
179             self.crawlers.discard(crawler)
180             self._active.discard(d)
181             return result
182 
183         return d.addBoth(_done)
184 
185     def create_crawler(self, crawler_or_spidercls):
186         """
187         Return a :class:`~scrapy.crawler.Crawler` object.
188 
189         * If `crawler_or_spidercls` is a Crawler, it is returned as-is.
190         * If `crawler_or_spidercls` is a Spider subclass, a new Crawler
191           is constructed for it.
192         * If `crawler_or_spidercls` is a string, this function finds
193           a spider with this name in a Scrapy project (using spider loader),
194           then creates a Crawler instance for it.
195         """
196         if isinstance(crawler_or_spidercls, Crawler):
197             return crawler_or_spidercls
198         return self._create_crawler(crawler_or_spidercls)
199 
200     def _create_crawler(self, spidercls):
201         if isinstance(spidercls, six.string_types):
202             spidercls = self.spider_loader.load(spidercls)
203         return Crawler(spidercls, self.settings)
204 
205     def stop(self):
206         """
207         Stops simultaneously all the crawling jobs taking place.
208 
209         Returns a deferred that is fired when they all have ended.
210         """
211         return defer.DeferredList([c.stop() for c in list(self.crawlers)])
212 
213     @defer.inlineCallbacks
214     def join(self):
215         """
216         join()
217 
218         Returns a deferred that is fired when all managed :attr:`crawlers` have
219         completed their executions.
220         """
221         while self._active:
222             yield defer.DeferredList(self._active)
223 
224 
225 class CrawlerProcess(CrawlerRunner):
226     """
227     A class to run multiple scrapy crawlers in a process simultaneously.
228 
229     This class extends :class:`~scrapy.crawler.CrawlerRunner` by adding support
230     for starting a Twisted `reactor`_ and handling shutdown signals, like the
231     keyboard interrupt command Ctrl-C. It also configures top-level logging.
232 
233     This utility should be a better fit than
234     :class:`~scrapy.crawler.CrawlerRunner` if you aren't running another
235     Twisted `reactor`_ within your application.
236 
237     The CrawlerProcess object must be instantiated with a
238     :class:`~scrapy.settings.Settings` object.
239 
240     :param install_root_handler: whether to install root logging handler
241         (default: True)
242 
243     This class shouldn't be needed (since Scrapy is responsible of using it
244     accordingly) unless writing scripts that manually handle the crawling
245     process. See :ref:`run-from-script` for an example.
246     """
247 
248     def __init__(self, settings=None, install_root_handler=True):
249         super(CrawlerProcess, self).__init__(settings)
250         install_shutdown_handlers(self._signal_shutdown)
251         configure_logging(self.settings, install_root_handler)
252         log_scrapy_info(self.settings)
253 
254     def _signal_shutdown(self, signum, _):
255         install_shutdown_handlers(self._signal_kill)
256         signame = signal_names[signum]
257         logger.info("Received %(signame)s, shutting down gracefully. Send again to force ",
258                     {'signame': signame})
259         reactor.callFromThread(self._graceful_stop_reactor)
260 
261     def _signal_kill(self, signum, _):
262         install_shutdown_handlers(signal.SIG_IGN)
263         signame = signal_names[signum]
264         logger.info('Received %(signame)s twice, forcing unclean shutdown',
265                     {'signame': signame})
266         reactor.callFromThread(self._stop_reactor)
267 
268     def start(self, stop_after_crawl=True):
269         """
270         This method starts a Twisted `reactor`_, adjusts its pool size to
271         :setting:`REACTOR_THREADPOOL_MAXSIZE`, and installs a DNS cache based
272         on :setting:`DNSCACHE_ENABLED` and :setting:`DNSCACHE_SIZE`.
273 
274         If `stop_after_crawl` is True, the reactor will be stopped after all
275         crawlers have finished, using :meth:`join`.
276 
277         :param boolean stop_after_crawl: stop or not the reactor when all
278             crawlers have finished
279         """
280         if stop_after_crawl:
281             d = self.join()
282             # Don't start the reactor if the deferreds are already fired
283             if d.called:
284                 return
285             d.addBoth(self._stop_reactor)
286 
287         reactor.installResolver(self._get_dns_resolver())
288         tp = reactor.getThreadPool()
289         tp.adjustPoolsize(maxthreads=self.settings.getint('REACTOR_THREADPOOL_MAXSIZE'))
290         reactor.addSystemEventTrigger('before', 'shutdown', self.stop)
291         reactor.run(installSignalHandlers=False)  # blocking call
292 
293     def _get_dns_resolver(self):
294         if self.settings.getbool('DNSCACHE_ENABLED'):
295             cache_size = self.settings.getint('DNSCACHE_SIZE')
296         else:
297             cache_size = 0
298         return CachingThreadedResolver(
299             reactor=reactor,
300             cache_size=cache_size,
301             timeout=self.settings.getfloat('DNS_TIMEOUT')
302         )
303 
304     def _graceful_stop_reactor(self):
305         d = self.stop()
306         d.addBoth(self._stop_reactor)
307         return d
308 
309     def _stop_reactor(self, _=None):
310         try:
311             reactor.stop()
312         except RuntimeError:  # raised if already stopped or in shutdown stage
313             pass
314 
315 
316 def _get_spider_loader(settings):
317     """ Get SpiderLoader instance from settings """
318     if settings.get('SPIDER_MANAGER_CLASS'):
319         warnings.warn(
320             'SPIDER_MANAGER_CLASS option is deprecated. '
321             'Please use SPIDER_LOADER_CLASS.',
322             category=ScrapyDeprecationWarning, stacklevel=2
323         )
324     cls_path = settings.get('SPIDER_MANAGER_CLASS',
325                             settings.get('SPIDER_LOADER_CLASS'))
326     loader_cls = load_object(cls_path)
327     try:
328         verifyClass(ISpiderLoader, loader_cls)
329     except DoesNotImplement:
330         warnings.warn(
331             'SPIDER_LOADER_CLASS (previously named SPIDER_MANAGER_CLASS) does '
332             'not fully implement scrapy.interfaces.ISpiderLoader interface. '
333             'Please add all missing methods to avoid unexpected runtime errors.',
334             category=ScrapyDeprecationWarning, stacklevel=2
335         )
336     return loader_cls.from_settings(settings.frozencopy())

1 import sys
2 from scrapy.cmdline import execute
3 
4 if __name__ == '__main__':
5     execute(["scrapy","github","--nolog"])