twisted/names/resolve.py

   1 # Copyright (c) Twisted Matrix Laboratories.
   2 # See LICENSE for details.
   3
   4
   5 """
   6 Lookup a name using multiple resolvers.
   7
   8 Future Plans: This needs someway to specify which resolver answered
   9 the query, or someway to specify (authority|ttl|cache behavior|more?)
  10
  11 @author: Jp Calderone
  12 """
  13
  14 from twisted.internet import defer, interfaces
  15 from twisted.names import dns
  16 from zope.interface import implements
  17 import common
  18
  19 class FailureHandler:
  20     def __init__(self, resolver, query, timeout):
  21         self.resolver = resolver
  22         self.query = query
  23         self.timeout = timeout
  24
  25
  26     def __call__(self, failure):
  27         # AuthoritativeDomainErrors should halt resolution attempts
  28         failure.trap(dns.DomainError, defer.TimeoutError, NotImplementedError)
  29         return self.resolver(self.query, self.timeout)
  30
  31
  32 class ResolverChain(common.ResolverBase):
  33     """Lookup an address using multiple C{IResolver}s"""
  34
  35     implements(interfaces.IResolver)
  36
  37
  38     def __init__(self, resolvers):
  39         common.ResolverBase.__init__(self)
  40         self.resolvers = resolvers
  41
  42
  43     def _lookup(self, name, cls, type, timeout):
  44         q = dns.Query(name, type, cls)
  45         d = self.resolvers[0].query(q, timeout)
  46         for r in self.resolvers[1:]:
  47             d = d.addErrback(
  48                 FailureHandler(r.query, q, timeout)
  49             )
  50         return d
  51
  52
  53     def lookupAllRecords(self, name, timeout = None):
  54         d = self.resolvers[0].lookupAllRecords(name, timeout)
  55         for r in self.resolvers[1:]:
  56             d = d.addErrback(
  57                 FailureHandler(r.lookupAllRecords, name, timeout)
  58             )
  59         return d