Clean transactions based on time. Add HttpTransactionCache tests.

tests/rest/client/test_transactions.py

@@ -0,0 +1,69 @@
+from synapse.rest.client.transactions import HttpTransactionCache
+from synapse.rest.client.transactions import CLEANUP_PERIOD_MS
+from twisted.internet import defer
+from mock import Mock, call
+from tests import unittest
+from tests.utils import MockClock
+
+
+class HttpTransactionCacheTestCase(unittest.TestCase):
+
+    def setUp(self):
+        self.clock = MockClock()
+        self.cache = HttpTransactionCache(self.clock)
+
+        self.mock_http_response = (200, "GOOD JOB!")
+        self.mock_key = "foo"
+
+    @defer.inlineCallbacks
+    def test_executes_given_function(self):
+        cb = Mock(
+            return_value=defer.succeed(self.mock_http_response)
+        )
+        res = yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "some_arg", keyword="arg"
+        )
+        cb.assert_called_once_with("some_arg", keyword="arg")
+        self.assertEqual(res, self.mock_http_response)
+
+    @defer.inlineCallbacks
+    def test_deduplicates_based_on_key(self):
+        cb = Mock(
+            return_value=defer.succeed(self.mock_http_response)
+        )
+        for i in range(3):  # invoke multiple times
+            res = yield self.cache.fetch_or_execute(
+                self.mock_key, cb, "some_arg", keyword="arg", changing_args=i
+            )
+            self.assertEqual(res, self.mock_http_response)
+        # expect only a single call to do the work
+        cb.assert_called_once_with("some_arg", keyword="arg", changing_args=0)
+
+    @defer.inlineCallbacks
+    def test_cleans_up(self):
+        cb = Mock(
+            return_value=defer.succeed(self.mock_http_response)
+        )
+        yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "an arg"
+        )
+        # should NOT have cleaned up yet
+        self.clock.advance_time_msec(CLEANUP_PERIOD_MS / 2)
+
+        yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "an arg"
+        )
+        # still using cache
+        cb.assert_called_once_with("an arg")
+
+        self.clock.advance_time_msec(CLEANUP_PERIOD_MS)
+
+        yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "an arg"
+        )
+        # no longer using cache
+        self.assertEqual(cb.call_count, 2)
+        self.assertEqual(
+            cb.call_args_list,
+            [call("an arg",), call("an arg",)]
+        )