Fixed presence results not returning offline users on initial sync (#17231)

This is to address an issue in which `m.presence` results on initial
sync are not returning entries of users who are currently offline.

The original behaviour was from
https://github.com/element-hq/synapse/issues/1535

This change is useful for applications that use the
presence system for tracking user profile information/updates (e.g.
https://github.com/element-hq/synapse/pull/16992 or for profile status
messages).

This is gated behind a new configuration option to avoid performance
impact for applications that don't need this, as a pragmatic solution
for now.

2 files changed, 10 insertions, 1 deletions

diff --git a/synapse/config/server.py b/synapse/config/server.py

index 8bb97df175..fd52c0475c 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -384,6 +384,11 @@ class ServerConfig(Config):
         # Whether to internally track presence, requires that presence is enabled,
         self.track_presence = self.presence_enabled and presence_enabled != "untracked"
 
+        # Determines if presence results for offline users are included on initial/full sync
+        self.presence_include_offline_users_on_sync = presence_config.get(
+            "include_offline_users_on_sync", False
+        )
+
         # Custom presence router module
         # This is the legacy way of configuring it (the config should now be put in the modules section)
         self.presence_router_module_class = None
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py

index de227faec3..ede014180c 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -2270,7 +2270,11 @@ class SyncHandler:
             user=user,
             from_key=presence_key,
             is_guest=sync_config.is_guest,
-            include_offline=include_offline,
+            include_offline=(
+                True
+                if self.hs_config.server.presence_include_offline_users_on_sync
+                else include_offline
+            ),
         )
         assert presence_key
         sync_result_builder.now_token = now_token.copy_and_replace(