From c955f22e2c88676944124a4a3c80112b35231035 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Fri, 11 Jun 2021 10:27:12 +0100
Subject: [PATCH] Fix bug when running presence off master (#10149)

Hopefully fixes #10027.
---
 changelog.d/10149.bugfix                   |  1 +
 synapse/storage/databases/main/presence.py |  2 +-
 synapse/storage/util/id_generators.py      | 15 +++++++++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/10149.bugfix

diff --git a/changelog.d/10149.bugfix b/changelog.d/10149.bugfix
new file mode 100644
index 000000000..cb2d2eedb
--- /dev/null
+++ b/changelog.d/10149.bugfix
@@ -0,0 +1 @@
+Fix a bug which caused  presence updates to stop working some time after restart, when using a presence writer worker.
diff --git a/synapse/storage/databases/main/presence.py b/synapse/storage/databases/main/presence.py
index 6a2baa784..1388771c4 100644
--- a/synapse/storage/databases/main/presence.py
+++ b/synapse/storage/databases/main/presence.py
@@ -50,7 +50,7 @@ class PresenceStore(SQLBaseStore):
                 instance_name=self._instance_name,
                 tables=[("presence_stream", "instance_name", "stream_id")],
                 sequence_name="presence_stream_sequence",
-                writers=hs.config.worker.writers.to_device,
+                writers=hs.config.worker.writers.presence,
             )
         else:
             self._presence_id_gen = StreamIdGenerator(
diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py
index b1bd3a52d..f1e62f9e8 100644
--- a/synapse/storage/util/id_generators.py
+++ b/synapse/storage/util/id_generators.py
@@ -397,6 +397,11 @@ class MultiWriterIdGenerator:
                 # ... persist event ...
         """
 
+        # If we have a list of instances that are allowed to write to this
+        # stream, make sure we're in it.
+        if self._writers and self._instance_name not in self._writers:
+            raise Exception("Tried to allocate stream ID on non-writer")
+
         return _MultiWriterCtxManager(self)
 
     def get_next_mult(self, n: int):
@@ -406,6 +411,11 @@ class MultiWriterIdGenerator:
                 # ... persist events ...
         """
 
+        # If we have a list of instances that are allowed to write to this
+        # stream, make sure we're in it.
+        if self._writers and self._instance_name not in self._writers:
+            raise Exception("Tried to allocate stream ID on non-writer")
+
         return _MultiWriterCtxManager(self, n)
 
     def get_next_txn(self, txn: LoggingTransaction):
@@ -416,6 +426,11 @@ class MultiWriterIdGenerator:
             # ... persist event ...
         """
 
+        # If we have a list of instances that are allowed to write to this
+        # stream, make sure we're in it.
+        if self._writers and self._instance_name not in self._writers:
+            raise Exception("Tried to allocate stream ID on non-writer")
+
         next_id = self._load_next_id_txn(txn)
 
         with self._lock: