From 1f9df1cc7ba7027aef3a38d01909a928ecf2a8c5 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Tue, 20 Aug 2019 11:49:44 +0100
Subject: Fixup _sort_server_list to be slightly more efficient
Also document that we are using the algorithm described in RFC2782 and
ensure we handle zero weight correctly.
---
synapse/http/federation/srv_resolver.py | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
(limited to 'synapse/http')
diff --git a/synapse/http/federation/srv_resolver.py b/synapse/http/federation/srv_resolver.py
index bbda0a23f4..110b112e85 100644
--- a/synapse/http/federation/srv_resolver.py
+++ b/synapse/http/federation/srv_resolver.py
@@ -94,10 +94,18 @@ def _sort_server_list(server_list):
results = []
for priority in sorted(priority_map):
- servers = priority_map.pop(priority)
+ servers = priority_map[priority]
+ # This algorithms follows the algorithm described in RFC2782.
+ #
+ # N.B. Weights can be zero, which means that you should pick that server
+ # last *or* that its the only server in this priority.
+
+ # We sort to ensure zero weighted items are first.
+ servers.sort(key=lambda s: s.weight)
+
+ total_weight = sum(s.weight for s in servers)
while servers:
- total_weight = sum(s.weight for s in servers)
target_weight = random.randint(0, total_weight)
for s in servers:
@@ -108,6 +116,7 @@ def _sort_server_list(server_list):
results.append(s)
servers.remove(s)
+ total_weight -= s.weight
return results
--
cgit 1.5.1