Replace DeferredCache with LruCache where possible (#8563)

Most of these uses don't need a full-blown DeferredCache; LruCache is lighter and more appropriate.

8 files changed, 30 insertions, 27 deletions

diff --git a/changelog.d/8563.misc b/changelog.d/8563.misc
new file mode 100644
index 0000000000..eeba8e5fee
--- /dev/null
+++ b/changelog.d/8563.misc
@@ -0,0 +1 @@
+Replace `DeferredCache` with the lighter-weight `LruCache` where possible.
diff --git a/synapse/replication/slave/storage/client_ips.py b/synapse/replication/slave/storage/client_ips.py
index 4b0ea0cc01..0f5b7adef7 100644
--- a/synapse/replication/slave/storage/client_ips.py
+++ b/synapse/replication/slave/storage/client_ips.py
@@ -15,7 +15,7 @@
 
 from synapse.storage.database import DatabasePool
 from synapse.storage.databases.main.client_ips import LAST_SEEN_GRANULARITY
-from synapse.util.caches.deferred_cache import DeferredCache
+from synapse.util.caches.lrucache import LruCache
 
 from ._base import BaseSlavedStore
 
@@ -24,9 +24,9 @@ class SlavedClientIpStore(BaseSlavedStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
         super().__init__(database, db_conn, hs)
 
-        self.client_ip_last_seen = DeferredCache(
-            name="client_ip_last_seen", keylen=4, max_entries=50000
-        )  # type: DeferredCache[tuple, int]
+        self.client_ip_last_seen = LruCache(
+            cache_name="client_ip_last_seen", keylen=4, max_size=50000
+        )  # type: LruCache[tuple, int]
 
     async def insert_client_ip(self, user_id, access_token, ip, user_agent, device_id):
         now = int(self._clock.time_msec())
@@ -41,7 +41,7 @@ class SlavedClientIpStore(BaseSlavedStore):
         if last_seen is not None and (now - last_seen) < LAST_SEEN_GRANULARITY:
             return
 
-        self.client_ip_last_seen.prefill(key, now)
+        self.client_ip_last_seen.set(key, now)
 
         self.hs.get_tcp_replication().send_user_ip(
             user_id, access_token, ip, user_agent, device_id, now
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index ab49d227de..2b196ded1b 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -76,14 +76,16 @@ class SQLBaseStore(metaclass=ABCMeta):
         """
 
         try:
-            if key is None:
-                getattr(self, cache_name).invalidate_all()
-            else:
-                getattr(self, cache_name).invalidate(tuple(key))
+            cache = getattr(self, cache_name)
         except AttributeError:
             # We probably haven't pulled in the cache in this worker,
             # which is fine.
-            pass
+            return
+
+        if key is None:
+            cache.invalidate_all()
+        else:
+            cache.invalidate(tuple(key))
 
 
 def db_to_json(db_content):
diff --git a/synapse/storage/databases/main/client_ips.py b/synapse/storage/databases/main/client_ips.py
index 9e66e6648a..339bd691a4 100644
--- a/synapse/storage/databases/main/client_ips.py
+++ b/synapse/storage/databases/main/client_ips.py
@@ -19,7 +19,7 @@ from typing import Dict, Optional, Tuple
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import DatabasePool, make_tuple_comparison_clause
-from synapse.util.caches.deferred_cache import DeferredCache
+from synapse.util.caches.lrucache import LruCache
 
 logger = logging.getLogger(__name__)
 
@@ -410,8 +410,8 @@ class ClientIpWorkerStore(ClientIpBackgroundUpdateStore):
 class ClientIpStore(ClientIpWorkerStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
 
-        self.client_ip_last_seen = DeferredCache(
-            name="client_ip_last_seen", keylen=4, max_entries=50000
+        self.client_ip_last_seen = LruCache(
+            cache_name="client_ip_last_seen", keylen=4, max_size=50000
         )
 
         super().__init__(database, db_conn, hs)
@@ -442,7 +442,7 @@ class ClientIpStore(ClientIpWorkerStore):
         if last_seen is not None and (now - last_seen) < LAST_SEEN_GRANULARITY:
             return
 
-        self.client_ip_last_seen.prefill(key, now)
+        self.client_ip_last_seen.set(key, now)
 
         self._batch_row_update[key] = (user_agent, device_id, now)
 
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index e662a20d24..dfb4f87b8f 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -34,8 +34,8 @@ from synapse.storage.database import (
 )
 from synapse.types import Collection, JsonDict, get_verify_key_from_cross_signing_key
 from synapse.util import json_decoder, json_encoder
-from synapse.util.caches.deferred_cache import DeferredCache
 from synapse.util.caches.descriptors import cached, cachedList
+from synapse.util.caches.lrucache import LruCache
 from synapse.util.iterutils import batch_iter
 from synapse.util.stringutils import shortstr
 
@@ -1005,8 +1005,8 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
 
         # Map of (user_id, device_id) -> bool. If there is an entry that implies
         # the device exists.
-        self.device_id_exists_cache = DeferredCache(
-            name="device_id_exists", keylen=2, max_entries=10000
+        self.device_id_exists_cache = LruCache(
+            cache_name="device_id_exists", keylen=2, max_size=10000
         )
 
     async def store_device(
@@ -1052,7 +1052,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
                 )
                 if hidden:
                     raise StoreError(400, "The device ID is in use", Codes.FORBIDDEN)
-            self.device_id_exists_cache.prefill(key, True)
+            self.device_id_exists_cache.set(key, True)
             return inserted
         except StoreError:
             raise
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index ba3b1769b0..87808c1483 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -1051,9 +1051,7 @@ class PersistEventsStore:
 
         def prefill():
             for cache_entry in to_prefill:
-                self.store._get_event_cache.prefill(
-                    (cache_entry[0].event_id,), cache_entry
-                )
+                self.store._get_event_cache.set((cache_entry[0].event_id,), cache_entry)
 
         txn.call_after(prefill)
 
diff --git a/synapse/storage/databases/main/events_worker.py b/synapse/storage/databases/main/events_worker.py
index 0ad9a19b3d..c342df2a8b 100644
--- a/synapse/storage/databases/main/events_worker.py
+++ b/synapse/storage/databases/main/events_worker.py
@@ -42,8 +42,8 @@ from synapse.storage.database import DatabasePool
 from synapse.storage.engines import PostgresEngine
 from synapse.storage.util.id_generators import MultiWriterIdGenerator, StreamIdGenerator
 from synapse.types import Collection, get_domain_from_id
-from synapse.util.caches.deferred_cache import DeferredCache
 from synapse.util.caches.descriptors import cached
+from synapse.util.caches.lrucache import LruCache
 from synapse.util.iterutils import batch_iter
 from synapse.util.metrics import Measure
 
@@ -146,11 +146,10 @@ class EventsWorkerStore(SQLBaseStore):
                 self._cleanup_old_transaction_ids,
             )
 
-        self._get_event_cache = DeferredCache(
-            "*getEvent*",
+        self._get_event_cache = LruCache(
+            cache_name="*getEvent*",
             keylen=3,
-            max_entries=hs.config.caches.event_cache_size,
-            apply_cache_factor_from_config=False,
+            max_size=hs.config.caches.event_cache_size,
         )
 
         self._event_fetch_lock = threading.Condition()
@@ -749,7 +748,7 @@ class EventsWorkerStore(SQLBaseStore):
                 event=original_ev, redacted_event=redacted_event
             )
 
-            self._get_event_cache.prefill((event_id,), cache_entry)
+            self._get_event_cache.set((event_id,), cache_entry)
             result_map[event_id] = cache_entry
 
         return result_map
diff --git a/synapse/util/caches/lrucache.py b/synapse/util/caches/lrucache.py
index 4e95dd9bf3..3b471d8fd3 100644
--- a/synapse/util/caches/lrucache.py
+++ b/synapse/util/caches/lrucache.py
@@ -337,6 +337,9 @@ class LruCache(Generic[KT, VT]):
         self.set = cache_set
         self.setdefault = cache_set_default
         self.pop = cache_pop
+        # `invalidate` is exposed for consistency with DeferredCache, so that it can be
+        # invalidated by the cache invalidation replication stream.
+        self.invalidate = cache_pop
         if cache_type is TreeCache:
             self.del_multi = cache_del_multi
         self.len = synchronized(cache_len)