Refactor and bugfix for resove_service (#4427)

tests/http/federation/test_srv_resolver.py

@@ -0,0 +1,209 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2019 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from mock import Mock
+
+from twisted.internet import defer
+from twisted.internet.defer import Deferred
+from twisted.internet.error import ConnectError
+from twisted.names import dns, error
+
+from synapse.http.federation.srv_resolver import resolve_service
+from synapse.util.logcontext import LoggingContext
+
+from tests import unittest
+from tests.utils import MockClock
+
+
+class SrvResolverTestCase(unittest.TestCase):
+    def test_resolve(self):
+        dns_client_mock = Mock()
+
+        service_name = b"test_service.example.com"
+        host_name = b"example.com"
+
+        answer_srv = dns.RRHeader(
+            type=dns.SRV, payload=dns.Record_SRV(target=host_name)
+        )
+
+        result_deferred = Deferred()
+        dns_client_mock.lookupService.return_value = result_deferred
+
+        cache = {}
+
+        @defer.inlineCallbacks
+        def do_lookup():
+            with LoggingContext("one") as ctx:
+                resolve_d = resolve_service(
+                    service_name, dns_client=dns_client_mock, cache=cache
+                )
+
+                self.assertNoResult(resolve_d)
+
+                # should have reset to the sentinel context
+                self.assertIs(LoggingContext.current_context(), LoggingContext.sentinel)
+
+                result = yield resolve_d
+
+                # should have restored our context
+                self.assertIs(LoggingContext.current_context(), ctx)
+
+                defer.returnValue(result)
+
+        test_d = do_lookup()
+        self.assertNoResult(test_d)
+
+        dns_client_mock.lookupService.assert_called_once_with(service_name)
+
+        result_deferred.callback(
+            ([answer_srv], None, None)
+        )
+
+        servers = self.successResultOf(test_d)
+
+        self.assertEquals(len(servers), 1)
+        self.assertEquals(servers, cache[service_name])
+        self.assertEquals(servers[0].host, host_name)
+
+    @defer.inlineCallbacks
+    def test_from_cache_expired_and_dns_fail(self):
+        dns_client_mock = Mock()
+        dns_client_mock.lookupService.return_value = defer.fail(error.DNSServerError())
+
+        service_name = "test_service.example.com"
+
+        entry = Mock(spec_set=["expires"])
+        entry.expires = 0
+
+        cache = {service_name: [entry]}
+
+        servers = yield resolve_service(
+            service_name, dns_client=dns_client_mock, cache=cache
+        )
+
+        dns_client_mock.lookupService.assert_called_once_with(service_name)
+
+        self.assertEquals(len(servers), 1)
+        self.assertEquals(servers, cache[service_name])
+
+    @defer.inlineCallbacks
+    def test_from_cache(self):
+        clock = MockClock()
+
+        dns_client_mock = Mock(spec_set=['lookupService'])
+        dns_client_mock.lookupService = Mock(spec_set=[])
+
+        service_name = "test_service.example.com"
+
+        entry = Mock(spec_set=["expires"])
+        entry.expires = 999999999
+
+        cache = {service_name: [entry]}
+
+        servers = yield resolve_service(
+            service_name, dns_client=dns_client_mock, cache=cache, clock=clock
+        )
+
+        self.assertFalse(dns_client_mock.lookupService.called)
+
+        self.assertEquals(len(servers), 1)
+        self.assertEquals(servers, cache[service_name])
+
+    @defer.inlineCallbacks
+    def test_empty_cache(self):
+        dns_client_mock = Mock()
+
+        dns_client_mock.lookupService.return_value = defer.fail(error.DNSServerError())
+
+        service_name = "test_service.example.com"
+
+        cache = {}
+
+        with self.assertRaises(error.DNSServerError):
+            yield resolve_service(service_name, dns_client=dns_client_mock, cache=cache)
+
+    @defer.inlineCallbacks
+    def test_name_error(self):
+        dns_client_mock = Mock()
+
+        dns_client_mock.lookupService.return_value = defer.fail(error.DNSNameError())
+
+        service_name = "test_service.example.com"
+
+        cache = {}
+
+        servers = yield resolve_service(
+            service_name, dns_client=dns_client_mock, cache=cache
+        )
+
+        self.assertEquals(len(servers), 0)
+        self.assertEquals(len(cache), 0)
+
+    def test_disabled_service(self):
+        """
+        test the behaviour when there is a single record which is ".".
+        """
+        service_name = b"test_service.example.com"
+
+        lookup_deferred = Deferred()
+        dns_client_mock = Mock()
+        dns_client_mock.lookupService.return_value = lookup_deferred
+        cache = {}
+
+        resolve_d = resolve_service(
+            service_name, dns_client=dns_client_mock, cache=cache
+        )
+        self.assertNoResult(resolve_d)
+
+        # returning a single "." should make the lookup fail with a ConenctError
+        lookup_deferred.callback((
+            [dns.RRHeader(type=dns.SRV, payload=dns.Record_SRV(target=b"."))],
+            None,
+            None,
+        ))
+
+        self.failureResultOf(resolve_d, ConnectError)
+
+    def test_non_srv_answer(self):
+        """
+        test the behaviour when the dns server gives us a spurious non-SRV response
+        """
+        service_name = b"test_service.example.com"
+
+        lookup_deferred = Deferred()
+        dns_client_mock = Mock()
+        dns_client_mock.lookupService.return_value = lookup_deferred
+        cache = {}
+
+        resolve_d = resolve_service(
+            service_name, dns_client=dns_client_mock, cache=cache
+        )
+        self.assertNoResult(resolve_d)
+
+        lookup_deferred.callback((
+            [
+                dns.RRHeader(type=dns.A, payload=dns.Record_A()),
+                dns.RRHeader(type=dns.SRV, payload=dns.Record_SRV(target=b"host")),
+            ],
+            None,
+            None,
+        ))
+
+        servers = self.successResultOf(resolve_d)
+
+        self.assertEquals(len(servers), 1)
+        self.assertEquals(servers, cache[service_name])
+        self.assertEquals(servers[0].host, b"host")