mirror of https://github.com/scrapy/scrapy.git
80 lines
3.0 KiB
Python
80 lines
3.0 KiB
Python
import logging
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import pprint
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from collections import defaultdict, deque
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from typing import Callable, Deque, Dict, Optional, cast, Iterable
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from twisted.internet.defer import Deferred
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from scrapy import Spider
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from scrapy.exceptions import NotConfigured
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from scrapy.settings import Settings
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from scrapy.utils.misc import create_instance, load_object
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from scrapy.utils.defer import process_parallel, process_chain
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logger = logging.getLogger(__name__)
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class MiddlewareManager:
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"""Base class for implementing middleware managers"""
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component_name = 'foo middleware'
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def __init__(self, *middlewares):
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self.middlewares = middlewares
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# Optional because process_spider_output and process_spider_exception can be None
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self.methods: Dict[str, Deque[Optional[Callable]]] = defaultdict(deque)
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for mw in middlewares:
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self._add_middleware(mw)
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@classmethod
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def _get_mwlist_from_settings(cls, settings: Settings) -> list:
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raise NotImplementedError
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@classmethod
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def from_settings(cls, settings: Settings, crawler=None):
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mwlist = cls._get_mwlist_from_settings(settings)
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middlewares = []
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enabled = []
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for clspath in mwlist:
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try:
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mwcls = load_object(clspath)
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mw = create_instance(mwcls, settings, crawler)
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middlewares.append(mw)
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enabled.append(clspath)
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except NotConfigured as e:
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if e.args:
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clsname = clspath.split('.')[-1]
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logger.warning("Disabled %(clsname)s: %(eargs)s",
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{'clsname': clsname, 'eargs': e.args[0]},
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extra={'crawler': crawler})
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logger.info("Enabled %(componentname)ss:\n%(enabledlist)s",
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{'componentname': cls.component_name,
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'enabledlist': pprint.pformat(enabled)},
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extra={'crawler': crawler})
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return cls(*middlewares)
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@classmethod
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def from_crawler(cls, crawler):
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return cls.from_settings(crawler.settings, crawler)
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def _add_middleware(self, mw) -> None:
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if hasattr(mw, 'open_spider'):
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self.methods['open_spider'].append(mw.open_spider)
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if hasattr(mw, 'close_spider'):
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self.methods['close_spider'].appendleft(mw.close_spider)
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def _process_parallel(self, methodname: str, obj, *args) -> Deferred:
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methods = cast(Iterable[Callable], self.methods[methodname])
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return process_parallel(methods, obj, *args)
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def _process_chain(self, methodname: str, obj, *args) -> Deferred:
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methods = cast(Iterable[Callable], self.methods[methodname])
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return process_chain(methods, obj, *args)
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def open_spider(self, spider: Spider) -> Deferred:
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return self._process_parallel('open_spider', spider)
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def close_spider(self, spider: Spider) -> Deferred:
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return self._process_parallel('close_spider', spider)
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