From 8a4fb7a6baf32a35c24056474d98fed525522b78 Mon Sep 17 00:00:00 2001 From: Matthew Ma Date: Thu, 17 Aug 2023 02:22:50 -0700 Subject: [PATCH] Disable caching in /sync corner case (#16080) Fixes #15502 --- changelog.d/16080.bugfix | 1 + synapse/handlers/sync.py | 20 ++++++++++---------- 2 files changed, 11 insertions(+), 10 deletions(-) create mode 100644 changelog.d/16080.bugfix diff --git a/changelog.d/16080.bugfix b/changelog.d/16080.bugfix new file mode 100644 index 0000000000..1ad6fb3c52 --- /dev/null +++ b/changelog.d/16080.bugfix @@ -0,0 +1 @@ +Fix a long-standing bu in `/sync` where timeout=0 does not skip caching, resulting in slow calls in cases where there are no new changes. Contributed by @PlasmaIntec. \ No newline at end of file diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py index 8174248387..60a9f341b5 100644 --- a/synapse/handlers/sync.py +++ b/synapse/handlers/sync.py @@ -387,16 +387,16 @@ 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 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():