From f4ad5eea67cd89a8a0ba76a03e781ee861e62608 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Fri, 2 Oct 2020 14:19:49 +0100
Subject: [PATCH 1/2] Speed up unit tests when using PostgreSQL

---
 synapse/storage/databases/main/events_worker.py | 13 ++++++++++++-
 tests/server.py                                 |  4 ++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/synapse/storage/databases/main/events_worker.py b/synapse/storage/databases/main/events_worker.py
index f95679ebc440..723ced4ff09d 100644
--- a/synapse/storage/databases/main/events_worker.py
+++ b/synapse/storage/databases/main/events_worker.py
@@ -74,6 +74,13 @@ class EventRedactBehaviour(Names):
 
 
 class EventsWorkerStore(SQLBaseStore):
+    # Whether to use dedicated DB threads for event fetching. This is only used
+    # if there are multiple DB threads available. When used will lock the DB
+    # thread for periods of time (so unit tests want to disable this when they
+    # run DB transactions on the main thread). See EVENT_QUEUE_* for more
+    # options controlling this.
+    USE_DEDICATED_DB_THREADS_FOR_EVENT_FETCHING = True
+
     def __init__(self, database: DatabasePool, db_conn, hs):
         super().__init__(database, db_conn, hs)
 
@@ -522,7 +529,11 @@ def _do_fetch(self, conn):
 
                 if not event_list:
                     single_threaded = self.database_engine.single_threaded
-                    if single_threaded or i > EVENT_QUEUE_ITERATIONS:
+                    if (
+                        not self.USE_DEDICATED_DB_THREADS_FOR_EVENT_FETCHING
+                        or single_threaded
+                        or i > EVENT_QUEUE_ITERATIONS
+                    ):
                         self._event_fetch_ongoing -= 1
                         return
                     else:
diff --git a/tests/server.py b/tests/server.py
index b404ad4e2a49..f7f5276b2152 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -372,6 +372,10 @@ def runInteraction(interaction, *args, **kwargs):
         pool.threadpool = ThreadPool(clock._reactor)
         pool.running = True
 
+    # We've just changed the Databases to run DB transactions on the same
+    # thread, so we need to disable the dedicated thread behaviour.
+    server.get_datastores().main.USE_DEDICATED_DB_THREADS_FOR_EVENT_FETCHING = False
+
     return server
 
 

From 672dda86d81e9548c96993efb68fe66fc61b17e2 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Fri, 2 Oct 2020 14:20:39 +0100
Subject: [PATCH 2/2] Newsfile

---
 changelog.d/8450.misc | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/8450.misc

diff --git a/changelog.d/8450.misc b/changelog.d/8450.misc
new file mode 100644
index 000000000000..4e04c523abef
--- /dev/null
+++ b/changelog.d/8450.misc
@@ -0,0 +1 @@
+Speed up unit tests when using PostgreSQL.