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# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Lookup a name using multiple resolvers.
Future Plans: This needs someway to specify which resolver answered
the query, or someway to specify (authority|ttl|cache behavior|more?)
@author: Jp Calderone
"""
from twisted.internet import defer, interfaces
from twisted.names import dns
from zope.interface import implements
import common
class FailureHandler:
def __init__(self, resolver, query, timeout):
self.resolver = resolver
self.query = query
self.timeout = timeout
def __call__(self, failure):
# AuthoritativeDomainErrors should halt resolution attempts
failure.trap(dns.DomainError, defer.TimeoutError, NotImplementedError)
return self.resolver(self.query, self.timeout)
class ResolverChain(common.ResolverBase):
"""Lookup an address using multiple C{IResolver}s"""
implements(interfaces.IResolver)
def __init__(self, resolvers):
common.ResolverBase.__init__(self)
self.resolvers = resolvers
def _lookup(self, name, cls, type, timeout):
q = dns.Query(name, type, cls)
d = self.resolvers[0].query(q, timeout)
for r in self.resolvers[1:]:
d = d.addErrback(
FailureHandler(r.query, q, timeout)
)
return d
def lookupAllRecords(self, name, timeout = None):
d = self.resolvers[0].lookupAllRecords(name, timeout)
for r in self.resolvers[1:]:
d = d.addErrback(
FailureHandler(r.lookupAllRecords, name, timeout)
)
return d
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