Prevent a sync request from removing a user's busy presence status (#12213)

In trying to use the MSC3026 busy presence status, the user's status
would be set back to 'online' next time they synced. This change makes
it so that syncing does not affect a user's presence status if it
is currently set to 'busy': it must be removed through the presence
API.

The MSC defers to implementations on the behaviour of busy presence,
so this ought to remain compatible with the MSC.

3 files changed, 53 insertions, 18 deletions

diff --git a/synapse/handlers/events.py b/synapse/handlers/events.py
index d2ccb5c5d3..e89c4df314 100644
--- a/synapse/handlers/events.py
+++ b/synapse/handlers/events.py
@@ -16,7 +16,7 @@ import logging
 import random
 from typing import TYPE_CHECKING, Iterable, List, Optional
 
-from synapse.api.constants import EduTypes, EventTypes, Membership
+from synapse.api.constants import EduTypes, EventTypes, Membership, PresenceState
 from synapse.api.errors import AuthError, SynapseError
 from synapse.events import EventBase
 from synapse.events.utils import SerializeEventConfig
@@ -67,7 +67,9 @@ class EventStreamHandler:
         presence_handler = self.hs.get_presence_handler()
 
         context = await presence_handler.user_syncing(
-            auth_user_id, affect_presence=affect_presence
+            auth_user_id,
+            affect_presence=affect_presence,
+            presence_state=PresenceState.ONLINE,
         )
         with context:
             if timeout:
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index 209a4b0e52..d078162c29 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -151,7 +151,7 @@ class BasePresenceHandler(abc.ABC):
 
     @abc.abstractmethod
     async def user_syncing(
-        self, user_id: str, affect_presence: bool
+        self, user_id: str, affect_presence: bool, presence_state: str
     ) -> ContextManager[None]:
         """Returns a context manager that should surround any stream requests
         from the user.
@@ -165,6 +165,7 @@ class BasePresenceHandler(abc.ABC):
             affect_presence: If false this function will be a no-op.
                 Useful for streams that are not associated with an actual
                 client that is being used by a user.
+            presence_state: The presence state indicated in the sync request
         """
 
     @abc.abstractmethod
@@ -228,6 +229,11 @@ class BasePresenceHandler(abc.ABC):
 
         return states
 
+    async def current_state_for_user(self, user_id: str) -> UserPresenceState:
+        """Get the current presence state for a user."""
+        res = await self.current_state_for_users([user_id])
+        return res[user_id]
+
     @abc.abstractmethod
     async def set_state(
         self,
@@ -461,7 +467,7 @@ class WorkerPresenceHandler(BasePresenceHandler):
                 self.send_user_sync(user_id, False, last_sync_ms)
 
     async def user_syncing(
-        self, user_id: str, affect_presence: bool
+        self, user_id: str, affect_presence: bool, presence_state: str
     ) -> ContextManager[None]:
         """Record that a user is syncing.
 
@@ -471,6 +477,17 @@ class WorkerPresenceHandler(BasePresenceHandler):
         if not affect_presence or not self._presence_enabled:
             return _NullContextManager()
 
+        prev_state = await self.current_state_for_user(user_id)
+        if prev_state != PresenceState.BUSY:
+            # We set state here but pass ignore_status_msg = True as we don't want to
+            # cause the status message to be cleared.
+            # Note that this causes last_active_ts to be incremented which is not
+            # what the spec wants: see comment in the BasePresenceHandler version
+            # of this function.
+            await self.set_state(
+                UserID.from_string(user_id), {"presence": presence_state}, True
+            )
+
         curr_sync = self._user_to_num_current_syncs.get(user_id, 0)
         self._user_to_num_current_syncs[user_id] = curr_sync + 1
 
@@ -942,7 +959,10 @@ class PresenceHandler(BasePresenceHandler):
         await self._update_states([prev_state.copy_and_replace(**new_fields)])
 
     async def user_syncing(
-        self, user_id: str, affect_presence: bool = True
+        self,
+        user_id: str,
+        affect_presence: bool = True,
+        presence_state: str = PresenceState.ONLINE,
     ) -> ContextManager[None]:
         """Returns a context manager that should surround any stream requests
         from the user.
@@ -956,6 +976,7 @@ class PresenceHandler(BasePresenceHandler):
             affect_presence: If false this function will be a no-op.
                 Useful for streams that are not associated with an actual
                 client that is being used by a user.
+            presence_state: The presence state indicated in the sync request
         """
         # Override if it should affect the user's presence, if presence is
         # disabled.
@@ -967,9 +988,25 @@ class PresenceHandler(BasePresenceHandler):
             self.user_to_num_current_syncs[user_id] = curr_sync + 1
 
             prev_state = await self.current_state_for_user(user_id)
+
+            # If they're busy then they don't stop being busy just by syncing,
+            # so just update the last sync time.
+            if prev_state.state != PresenceState.BUSY:
+                # XXX: We set_state separately here and just update the last_active_ts above
+                # This keeps the logic as similar as possible between the worker and single
+                # process modes. Using set_state will actually cause last_active_ts to be
+                # updated always, which is not what the spec calls for, but synapse has done
+                # this for... forever, I think.
+                await self.set_state(
+                    UserID.from_string(user_id), {"presence": presence_state}, True
+                )
+                # Retrieve the new state for the logic below. This should come from the
+                # in-memory cache.
+                prev_state = await self.current_state_for_user(user_id)
+
+            # To keep the single process behaviour consistent with worker mode, run the
+            # same logic as `update_external_syncs_row`, even though it looks weird.
             if prev_state.state == PresenceState.OFFLINE:
-                # If they're currently offline then bring them online, otherwise
-                # just update the last sync times.
                 await self._update_states(
                     [
                         prev_state.copy_and_replace(
@@ -979,6 +1016,10 @@ class PresenceHandler(BasePresenceHandler):
                         )
                     ]
                 )
+            # otherwise, set the new presence state & update the last sync time,
+            # but don't update last_active_ts as this isn't an indication that
+            # they've been active (even though it's probably been updated by
+            # set_state above)
             else:
                 await self._update_states(
                     [
@@ -1086,11 +1127,6 @@ class PresenceHandler(BasePresenceHandler):
             )
             self.external_process_last_updated_ms.pop(process_id, None)
 
-    async def current_state_for_user(self, user_id: str) -> UserPresenceState:
-        """Get the current presence state for a user."""
-        res = await self.current_state_for_users([user_id])
-        return res[user_id]
-
     async def _persist_and_notify(self, states: List[UserPresenceState]) -> None:
         """Persist states in the database, poke the notifier and send to
         interested remote servers
diff --git a/synapse/rest/client/sync.py b/synapse/rest/client/sync.py
index 2e25e8638b..e8772f86e7 100644
--- a/synapse/rest/client/sync.py
+++ b/synapse/rest/client/sync.py
@@ -180,13 +180,10 @@ class SyncRestServlet(RestServlet):
 
         affect_presence = set_presence != PresenceState.OFFLINE
 
-        if affect_presence:
-            await self.presence_handler.set_state(
-                user, {"presence": set_presence}, True
-            )
-
         context = await self.presence_handler.user_syncing(
-            user.to_string(), affect_presence=affect_presence
+            user.to_string(),
+            affect_presence=affect_presence,
+            presence_state=set_presence,
         )
         with context:
             sync_result = await self.sync_handler.wait_for_sync_for_user(