126 lines
3.7 KiB
Python
126 lines
3.7 KiB
Python
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# -*- test-case-name: twisted.names.test -*-
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# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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"""
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An in-memory caching resolver.
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"""
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from __future__ import division, absolute_import
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from twisted.names import dns, common
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from twisted.python import failure, log
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from twisted.internet import defer
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class CacheResolver(common.ResolverBase):
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"""
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A resolver that serves records from a local, memory cache.
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@ivar _reactor: A provider of L{interfaces.IReactorTime}.
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"""
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cache = None
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def __init__(self, cache=None, verbose=0, reactor=None):
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common.ResolverBase.__init__(self)
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self.cache = {}
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self.verbose = verbose
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self.cancel = {}
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if reactor is None:
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from twisted.internet import reactor
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self._reactor = reactor
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if cache:
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for query, (seconds, payload) in cache.items():
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self.cacheResult(query, payload, seconds)
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def __setstate__(self, state):
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self.__dict__ = state
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now = self._reactor.seconds()
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for (k, (when, (ans, add, ns))) in self.cache.items():
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diff = now - when
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for rec in ans + add + ns:
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if rec.ttl < diff:
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del self.cache[k]
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break
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def __getstate__(self):
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for c in self.cancel.values():
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c.cancel()
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self.cancel.clear()
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return self.__dict__
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def _lookup(self, name, cls, type, timeout):
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now = self._reactor.seconds()
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q = dns.Query(name, type, cls)
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try:
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when, (ans, auth, add) = self.cache[q]
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except KeyError:
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if self.verbose > 1:
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log.msg('Cache miss for ' + repr(name))
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return defer.fail(failure.Failure(dns.DomainError(name)))
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else:
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if self.verbose:
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log.msg('Cache hit for ' + repr(name))
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diff = now - when
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try:
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result = (
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[dns.RRHeader(r.name.name, r.type, r.cls, r.ttl - diff,
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r.payload) for r in ans],
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[dns.RRHeader(r.name.name, r.type, r.cls, r.ttl - diff,
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r.payload) for r in auth],
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[dns.RRHeader(r.name.name, r.type, r.cls, r.ttl - diff,
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r.payload) for r in add])
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except ValueError:
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return defer.fail(failure.Failure(dns.DomainError(name)))
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else:
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return defer.succeed(result)
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def lookupAllRecords(self, name, timeout = None):
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return defer.fail(failure.Failure(dns.DomainError(name)))
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def cacheResult(self, query, payload, cacheTime=None):
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"""
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Cache a DNS entry.
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@param query: a L{dns.Query} instance.
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@param payload: a 3-tuple of lists of L{dns.RRHeader} records, the
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matching result of the query (answers, authority and additional).
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@param cacheTime: The time (seconds since epoch) at which the entry is
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considered to have been added to the cache. If C{None} is given,
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the current time is used.
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"""
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if self.verbose > 1:
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log.msg('Adding %r to cache' % query)
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self.cache[query] = (cacheTime or self._reactor.seconds(), payload)
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if query in self.cancel:
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self.cancel[query].cancel()
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s = list(payload[0]) + list(payload[1]) + list(payload[2])
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if s:
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m = s[0].ttl
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for r in s:
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m = min(m, r.ttl)
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else:
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m = 0
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self.cancel[query] = self._reactor.callLater(m, self.clearEntry, query)
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def clearEntry(self, query):
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del self.cache[query]
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del self.cancel[query]
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