From a219ce87263ad9be887cf039a04b4a1f06b7b0b8 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Tue, 18 Sep 2018 18:27:37 +0100
Subject: [PATCH] Use directory server for room joins (#3899)

When we do a join, always try the server we used for the alias lookup first.

Fixes #2418
---
 changelog.d/3899.bugfix         | 1 +
 synapse/handlers/room_member.py | 5 +++++
 2 files changed, 6 insertions(+)
 create mode 100644 changelog.d/3899.bugfix

diff --git a/changelog.d/3899.bugfix b/changelog.d/3899.bugfix
new file mode 100644
index 0000000000..5120e3a823
--- /dev/null
+++ b/changelog.d/3899.bugfix
@@ -0,0 +1 @@
+When we join a room, always try the server we used for the alias lookup first, to avoid unresponsive and out-of-date servers.
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index f643619047..07fd3e82fc 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -583,6 +583,11 @@ class RoomMemberHandler(object):
         room_id = mapping["room_id"]
         servers = mapping["servers"]
 
+        # put the server which owns the alias at the front of the server list.
+        if room_alias.domain in servers:
+            servers.remove(room_alias.domain)
+        servers.insert(0, room_alias.domain)
+
         defer.returnValue((RoomID.from_string(room_id), servers))
 
     @defer.inlineCallbacks