32 lines
1.1 KiB
Python
32 lines
1.1 KiB
Python
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from twisted.internet import defer
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from twisted.internet.base import ThreadedResolver
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from scrapy.utils.datatypes import LocalCache
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# TODO: cache misses
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dnscache = LocalCache(10000)
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class CachingThreadedResolver(ThreadedResolver):
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def __init__(self, reactor, cache_size, timeout):
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super(CachingThreadedResolver, self).__init__(reactor)
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dnscache.limit = cache_size
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self.timeout = timeout
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def getHostByName(self, name, timeout=None):
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if name in dnscache:
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return defer.succeed(dnscache[name])
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# in Twisted<=16.6, getHostByName() is always called with
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# a default timeout of 60s (actually passed as (1, 3, 11, 45) tuple),
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# so the input argument above is simply overridden
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# to enforce Scrapy's DNS_TIMEOUT setting's value
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timeout = (self.timeout,)
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d = super(CachingThreadedResolver, self).getHostByName(name, timeout)
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if dnscache.limit:
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d.addCallback(self._cache_result, name)
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return d
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def _cache_result(self, result, name):
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dnscache[name] = result
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return result
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