Fix bug when running presence off master (#10149)

Hopefully fixes #10027.

1 files changed, 15 insertions, 0 deletions

diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py

index b1bd3a52d9..f1e62f9e85 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: