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Merge pull request #677 from matrix-org/erikj/dns_cache
Read from DNS cache if within TTL
This commit is contained in:
commit
79fc4ff6f9
2 changed files with 55 additions and 18 deletions
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@ -22,6 +22,7 @@ from twisted.names.error import DNSNameError, DomainError
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import collections
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import logging
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import random
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import time
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logger = logging.getLogger(__name__)
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@ -31,7 +32,7 @@ SERVER_CACHE = {}
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_Server = collections.namedtuple(
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"_Server", "priority weight host port"
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"_Server", "priority weight host port expires"
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)
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@ -92,7 +93,8 @@ class SRVClientEndpoint(object):
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host=domain,
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port=default_port,
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priority=0,
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weight=0
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weight=0,
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expires=0,
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)
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else:
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self.default_server = None
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@ -153,7 +155,13 @@ class SRVClientEndpoint(object):
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@defer.inlineCallbacks
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def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE):
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def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=time):
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cache_entry = cache.get(service_name, None)
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if cache_entry:
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if all(s.expires > int(clock.time()) for s in cache_entry):
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servers = list(cache_entry)
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defer.returnValue(servers)
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servers = []
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try:
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@ -173,27 +181,26 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE):
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continue
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payload = answer.payload
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host = str(payload.target)
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srv_ttl = answer.ttl
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try:
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answers, _, _ = yield dns_client.lookupAddress(host)
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except DNSNameError:
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continue
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ips = [
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answer.payload.dottedQuad()
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for answer in answers
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if answer.type == dns.A and answer.payload
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]
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for answer in answers:
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if answer.type == dns.A and answer.payload:
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ip = answer.payload.dottedQuad()
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host_ttl = min(srv_ttl, answer.ttl)
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for ip in ips:
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servers.append(_Server(
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host=ip,
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port=int(payload.port),
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priority=int(payload.priority),
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weight=int(payload.weight)
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))
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servers.append(_Server(
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host=ip,
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port=int(payload.port),
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priority=int(payload.priority),
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weight=int(payload.weight),
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expires=int(clock.time()) + host_ttl,
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))
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servers.sort()
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cache[service_name] = list(servers)
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@ -21,6 +21,8 @@ from mock import Mock
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from synapse.http.endpoint import resolve_service
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from tests.utils import MockClock
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class DnsTestCase(unittest.TestCase):
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@ -63,14 +65,17 @@ class DnsTestCase(unittest.TestCase):
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self.assertEquals(servers[0].host, ip_address)
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@defer.inlineCallbacks
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def test_from_cache(self):
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def test_from_cache_expired_and_dns_fail(self):
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dns_client_mock = Mock()
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dns_client_mock.lookupService.return_value = defer.fail(error.DNSServerError())
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service_name = "test_service.examle.com"
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entry = Mock(spec_set=["expires"])
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entry.expires = 0
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cache = {
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service_name: [object()]
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service_name: [entry]
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}
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servers = yield resolve_service(
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@ -82,6 +87,31 @@ class DnsTestCase(unittest.TestCase):
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self.assertEquals(len(servers), 1)
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self.assertEquals(servers, cache[service_name])
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@defer.inlineCallbacks
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def test_from_cache(self):
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clock = MockClock()
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dns_client_mock = Mock(spec_set=['lookupService'])
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dns_client_mock.lookupService = Mock(spec_set=[])
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service_name = "test_service.examle.com"
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entry = Mock(spec_set=["expires"])
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entry.expires = 999999999
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cache = {
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service_name: [entry]
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}
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servers = yield resolve_service(
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service_name, dns_client=dns_client_mock, cache=cache, clock=clock,
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)
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self.assertFalse(dns_client_mock.lookupService.called)
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self.assertEquals(len(servers), 1)
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self.assertEquals(servers, cache[service_name])
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@defer.inlineCallbacks
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def test_empty_cache(self):
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dns_client_mock = Mock()
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