diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 7f2138d804..b9a0361059 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -49,7 +49,7 @@ from synapse.types import (
from synapse.util.async_helpers import concurrently_execute
from synapse.util.caches.expiringcache import ExpiringCache
from synapse.util.caches.lrucache import LruCache
-from synapse.util.caches.response_cache import ResponseCache
+from synapse.util.caches.response_cache import ResponseCache, ResponseCacheContext
from synapse.util.metrics import Measure, measure_func
from synapse.visibility import filter_events_for_client
@@ -83,12 +83,15 @@ LAZY_LOADED_MEMBERS_CACHE_MAX_AGE = 30 * 60 * 1000
LAZY_LOADED_MEMBERS_CACHE_MAX_SIZE = 100
+SyncRequestKey = Tuple[Any, ...]
+
+
@attr.s(slots=True, frozen=True)
class SyncConfig:
user = attr.ib(type=UserID)
filter_collection = attr.ib(type=FilterCollection)
is_guest = attr.ib(type=bool)
- request_key = attr.ib(type=Tuple[Any, ...])
+ request_key = attr.ib(type=SyncRequestKey)
device_id = attr.ib(type=Optional[str])
@@ -266,9 +269,9 @@ class SyncHandler:
self.presence_handler = hs.get_presence_handler()
self.event_sources = hs.get_event_sources()
self.clock = hs.get_clock()
- self.response_cache = ResponseCache(
+ self.response_cache: ResponseCache[SyncRequestKey] = ResponseCache(
hs.get_clock(), "sync"
- ) # type: ResponseCache[Tuple[Any, ...]]
+ )
self.state = hs.get_state_handler()
self.auth = hs.get_auth()
self.storage = hs.get_storage()
@@ -307,6 +310,7 @@ class SyncHandler:
since_token,
timeout,
full_state,
+ cache_context=True,
)
logger.debug("Returning sync response for %s", user_id)
return res
@@ -314,9 +318,10 @@ class SyncHandler:
async def _wait_for_sync_for_user(
self,
sync_config: SyncConfig,
- since_token: Optional[StreamToken] = None,
- timeout: int = 0,
- full_state: bool = False,
+ since_token: Optional[StreamToken],
+ timeout: int,
+ full_state: bool,
+ cache_context: ResponseCacheContext[SyncRequestKey],
) -> SyncResult:
if since_token is None:
sync_type = "initial_sync"
@@ -343,13 +348,13 @@ class SyncHandler:
if timeout == 0 or since_token is None or full_state:
# we are going to return immediately, so don't bother calling
# notifier.wait_for_events.
- result = await self.current_sync_for_user(
+ result: SyncResult = await self.current_sync_for_user(
sync_config, since_token, full_state=full_state
)
else:
- def current_sync_callback(before_token, after_token):
- return self.current_sync_for_user(sync_config, since_token)
+ async def current_sync_callback(before_token, after_token) -> SyncResult:
+ return await self.current_sync_for_user(sync_config, since_token)
result = await self.notifier.wait_for_events(
sync_config.user.to_string(),
@@ -358,6 +363,17 @@ class SyncHandler:
from_token=since_token,
)
+ # if nothing has happened in any of the users' rooms since /sync was called,
+ # the resultant next_batch will be the same as since_token (since the result
+ # is generated when wait_for_events is first called, and not regenerated
+ # when wait_for_events times out).
+ #
+ # If that happens, we mustn't cache it, so that when the client comes back
+ # with the same cache token, we don't immediately return the same empty
+ # result, causing a tightloop. (#8518)
+ if result.next_batch == since_token:
+ cache_context.should_cache = False
+
if result:
if sync_config.filter_collection.lazy_load_members():
lazy_loaded = "true"
|
