Clean transactions based on time. Add HttpTransactionCache tests.

5 files changed, 99 insertions, 8 deletions

diff --git a/synapse/rest/client/transactions.py b/synapse/rest/client/transactions.py
index 8d69e12d36..351170edbc 100644
--- a/synapse/rest/client/transactions.py
+++ b/synapse/rest/client/transactions.py
@@ -41,12 +41,19 @@ def get_transaction_key(request):
     return request.path + "/" + token
 
 
+CLEANUP_PERIOD_MS = 1000 * 60 * 30  # 30 mins
+
+
 class HttpTransactionCache(object):
 
-    def __init__(self):
+    def __init__(self, clock):
+        self.clock = clock
         self.transactions = {
-            # $txn_key: ObservableDeferred<(res_code, res_json_body)>
+            # $txn_key: (ObservableDeferred<(res_code, res_json_body)>, timestamp)
         }
+        # Try to clean entries every 30 mins. This means entries will exist
+        # for at *LEAST* 30 mins, and at *MOST* 60 mins.
+        self.cleaner = self.clock.looping_call(self._cleanup, CLEANUP_PERIOD_MS)
 
     def fetch_or_execute_request(self, request, fn, *args, **kwargs):
         """A helper function for fetch_or_execute which extracts
@@ -74,11 +81,18 @@ class HttpTransactionCache(object):
             Deferred which resolves to a tuple of (response_code, response_dict).
         """
         try:
-            return self.transactions[txn_key].observe()
-        except KeyError:
+            return self.transactions[txn_key][0].observe()
+        except (KeyError, IndexError):
             pass  # execute the function instead.
 
         deferred = fn(*args, **kwargs)
         observable = ObservableDeferred(deferred)
-        self.transactions[txn_key] = observable
+        self.transactions[txn_key] = (observable, self.clock.time_msec())
         return observable.observe()
+
+    def _cleanup(self):
+        now = self.clock.time_msec()
+        for key in self.transactions.keys():
+            ts = self.transactions[key][1]
+            if now > (ts + CLEANUP_PERIOD_MS):  # after cleanup period
+                del self.transactions[key]
diff --git a/synapse/rest/client/v1/base.py b/synapse/rest/client/v1/base.py
index 07ff5b218c..c7aa0bbf59 100644
--- a/synapse/rest/client/v1/base.py
+++ b/synapse/rest/client/v1/base.py
@@ -60,4 +60,4 @@ class ClientV1RestServlet(RestServlet):
         self.hs = hs
         self.builder_factory = hs.get_event_builder_factory()
         self.auth = hs.get_v1auth()
-        self.txns = HttpTransactionCache()
+        self.txns = HttpTransactionCache(hs.get_clock())
diff --git a/synapse/rest/client/v2_alpha/sendtodevice.py b/synapse/rest/client/v2_alpha/sendtodevice.py
index 2187350d42..ac660669f3 100644
--- a/synapse/rest/client/v2_alpha/sendtodevice.py
+++ b/synapse/rest/client/v2_alpha/sendtodevice.py
@@ -40,7 +40,7 @@ class SendToDeviceRestServlet(servlet.RestServlet):
         super(SendToDeviceRestServlet, self).__init__()
         self.hs = hs
         self.auth = hs.get_auth()
-        self.txns = HttpTransactionCache()
+        self.txns = HttpTransactionCache(hs.get_clock())
         self.device_message_handler = hs.get_device_message_handler()
 
     def on_PUT(self, request, message_type, txn_id):
diff --git a/synapse/util/__init__.py b/synapse/util/__init__.py
index 2b3f0bef3c..c05b9450be 100644
--- a/synapse/util/__init__.py
+++ b/synapse/util/__init__.py
@@ -34,7 +34,7 @@ class Clock(object):
     """A small utility that obtains current time-of-day so that time may be
     mocked during unit-tests.
 
-    TODO(paul): Also move the sleep() functionallity into it
+    TODO(paul): Also move the sleep() functionality into it
     """
 
     def time(self):
@@ -46,6 +46,14 @@ class Clock(object):
         return int(self.time() * 1000)
 
     def looping_call(self, f, msec):
+        """Call a function repeatedly.
+
+         Waits `msec` initially before calling `f` for the first time.
+
+        Args:
+            f(function): The function to call repeatedly.
+            msec(float): How long to wait between calls in milliseconds.
+        """
         l = task.LoopingCall(f)
         l.start(msec / 1000.0, now=False)
         return l
diff --git a/tests/rest/client/test_transactions.py b/tests/rest/client/test_transactions.py
new file mode 100644
index 0000000000..d7cea30260
--- /dev/null
+++ b/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",)]
+        )