Split the state_group_cache in two (#3726)

Splits the state_group_cache in two.

One half contains normal state events; the other contains member events.

The idea is that the lazyloading common case of: "I want a subset of member events plus all of the other state" can be accomplished efficiently by splitting the cache into two, and asking for "all events" from the non-members cache, and "just these keys" from the members cache.  This means we can avoid having to make DictionaryCache aware of these sort of complicated queries, whilst letting LL requests benefit from the caching.

Previously we were unable to sensibly use the caching and had to pull all state from the DB irrespective of the filtering, which made things slow.  Hopefully fixes https://github.com/matrix-org/synapse/issues/3720.

1 files changed, 94 insertions, 11 deletions

diff --git a/tests/storage/test_state.py b/tests/storage/test_state.py

index ebfd969b36..d717b9f94e 100644
--- a/tests/storage/test_state.py
+++ b/tests/storage/test_state.py
@@ -185,6 +185,7 @@ class StateStoreTestCase(tests.unittest.TestCase):
 
         # test _get_some_state_from_cache correctly filters out members with types=[]
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_cache,
             group, [], filtered_types=[EventTypes.Member]
         )
 
@@ -197,8 +198,20 @@ class StateStoreTestCase(tests.unittest.TestCase):
             state_dict,
         )
 
+        (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
+            group, [], filtered_types=[EventTypes.Member]
+        )
+
+        self.assertEqual(is_all, True)
+        self.assertDictEqual(
+            {},
+            state_dict,
+        )
+
         # test _get_some_state_from_cache correctly filters in members with wildcard types
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_cache,
             group, [(EventTypes.Member, None)], filtered_types=[EventTypes.Member]
         )
 
@@ -207,6 +220,18 @@ class StateStoreTestCase(tests.unittest.TestCase):
             {
                 (e1.type, e1.state_key): e1.event_id,
                 (e2.type, e2.state_key): e2.event_id,
+            },
+            state_dict,
+        )
+
+        (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
+            group, [(EventTypes.Member, None)], filtered_types=[EventTypes.Member]
+        )
+
+        self.assertEqual(is_all, True)
+        self.assertDictEqual(
+            {
                 (e3.type, e3.state_key): e3.event_id,
                 # e4 is overwritten by e5
                 (e5.type, e5.state_key): e5.event_id,
@@ -216,6 +241,7 @@ class StateStoreTestCase(tests.unittest.TestCase):
 
         # test _get_some_state_from_cache correctly filters in members with specific types
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_cache,
             group,
             [(EventTypes.Member, e5.state_key)],
             filtered_types=[EventTypes.Member],
@@ -226,6 +252,20 @@ class StateStoreTestCase(tests.unittest.TestCase):
             {
                 (e1.type, e1.state_key): e1.event_id,
                 (e2.type, e2.state_key): e2.event_id,
+            },
+            state_dict,
+        )
+
+        (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
+            group,
+            [(EventTypes.Member, e5.state_key)],
+            filtered_types=[EventTypes.Member],
+        )
+
+        self.assertEqual(is_all, True)
+        self.assertDictEqual(
+            {
                 (e5.type, e5.state_key): e5.event_id,
             },
             state_dict,
@@ -234,6 +274,7 @@ class StateStoreTestCase(tests.unittest.TestCase):
         # test _get_some_state_from_cache correctly filters in members with specific types
         # and no filtered_types
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
             group, [(EventTypes.Member, e5.state_key)], filtered_types=None
         )
 
@@ -254,9 +295,6 @@ class StateStoreTestCase(tests.unittest.TestCase):
             {
                 (e1.type, e1.state_key): e1.event_id,
                 (e2.type, e2.state_key): e2.event_id,
-                (e3.type, e3.state_key): e3.event_id,
-                # e4 is overwritten by e5
-                (e5.type, e5.state_key): e5.event_id,
             },
         )
 
@@ -269,8 +307,6 @@ class StateStoreTestCase(tests.unittest.TestCase):
             # list fetched keys so it knows it's partial
             fetched_keys=(
                 (e1.type, e1.state_key),
-                (e3.type, e3.state_key),
-                (e5.type, e5.state_key),
             ),
         )
 
@@ -284,8 +320,6 @@ class StateStoreTestCase(tests.unittest.TestCase):
             set(
                 [
                     (e1.type, e1.state_key),
-                    (e3.type, e3.state_key),
-                    (e5.type, e5.state_key),
                 ]
             ),
         )
@@ -293,8 +327,6 @@ class StateStoreTestCase(tests.unittest.TestCase):
             state_dict_ids,
             {
                 (e1.type, e1.state_key): e1.event_id,
-                (e3.type, e3.state_key): e3.event_id,
-                (e5.type, e5.state_key): e5.event_id,
             },
         )
 
@@ -304,14 +336,25 @@ class StateStoreTestCase(tests.unittest.TestCase):
         # test _get_some_state_from_cache correctly filters out members with types=[]
         room_id = self.room.to_string()
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_cache,
             group, [], filtered_types=[EventTypes.Member]
         )
 
         self.assertEqual(is_all, False)
         self.assertDictEqual({(e1.type, e1.state_key): e1.event_id}, state_dict)
 
+        room_id = self.room.to_string()
+        (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
+            group, [], filtered_types=[EventTypes.Member]
+        )
+
+        self.assertEqual(is_all, True)
+        self.assertDictEqual({}, state_dict)
+
         # test _get_some_state_from_cache correctly filters in members wildcard types
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_cache,
             group, [(EventTypes.Member, None)], filtered_types=[EventTypes.Member]
         )
 
@@ -319,8 +362,19 @@ class StateStoreTestCase(tests.unittest.TestCase):
         self.assertDictEqual(
             {
                 (e1.type, e1.state_key): e1.event_id,
+            },
+            state_dict,
+        )
+
+        (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
+            group, [(EventTypes.Member, None)], filtered_types=[EventTypes.Member]
+        )
+
+        self.assertEqual(is_all, True)
+        self.assertDictEqual(
+            {
                 (e3.type, e3.state_key): e3.event_id,
-                # e4 is overwritten by e5
                 (e5.type, e5.state_key): e5.event_id,
             },
             state_dict,
@@ -328,6 +382,7 @@ class StateStoreTestCase(tests.unittest.TestCase):
 
         # test _get_some_state_from_cache correctly filters in members with specific types
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_cache,
             group,
             [(EventTypes.Member, e5.state_key)],
             filtered_types=[EventTypes.Member],
@@ -337,6 +392,20 @@ class StateStoreTestCase(tests.unittest.TestCase):
         self.assertDictEqual(
             {
                 (e1.type, e1.state_key): e1.event_id,
+            },
+            state_dict,
+        )
+
+        (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
+            group,
+            [(EventTypes.Member, e5.state_key)],
+            filtered_types=[EventTypes.Member],
+        )
+
+        self.assertEqual(is_all, True)
+        self.assertDictEqual(
+            {
                 (e5.type, e5.state_key): e5.event_id,
             },
             state_dict,
@@ -345,8 +414,22 @@ class StateStoreTestCase(tests.unittest.TestCase):
         # test _get_some_state_from_cache correctly filters in members with specific types
         # and no filtered_types
         (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_cache,
+            group, [(EventTypes.Member, e5.state_key)], filtered_types=None
+        )
+
+        self.assertEqual(is_all, False)
+        self.assertDictEqual({}, state_dict)
+
+        (state_dict, is_all) = yield self.store._get_some_state_from_cache(
+            self.store._state_group_members_cache,
             group, [(EventTypes.Member, e5.state_key)], filtered_types=None
         )
 
         self.assertEqual(is_all, True)
-        self.assertDictEqual({(e5.type, e5.state_key): e5.event_id}, state_dict)
+        self.assertDictEqual(
+            {
+                (e5.type, e5.state_key): e5.event_id,
+            },
+            state_dict,
+        )