From 34e4c8f5738a5614339caef09a60c5d81e80d8e4 Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <tgx_world@hotmail.com>
Date: Tue, 19 Jun 2018 10:15:29 +0800
Subject: [PATCH] FIX: `Discourse.keep_readonly_mode` spins a new thread each
 time it is called.

---
 lib/discourse.rb | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/lib/discourse.rb b/lib/discourse.rb
index 0822630eead..f42caae4f49 100644
--- a/lib/discourse.rb
+++ b/lib/discourse.rb
@@ -294,10 +294,16 @@ module Discourse
   def self.keep_readonly_mode(key)
     # extend the expiry by 1 minute every 30 seconds
     unless Rails.env.test?
-      Thread.new do
-        while readonly_mode?(key)
-          $redis.expire(key, READONLY_MODE_KEY_TTL)
-          sleep 30.seconds
+      @threads ||= {}
+
+      active_thread = @threads[key]
+
+      unless active_thread&.alive?
+        @threads[key] = Thread.new do
+          while readonly_mode?(key)
+            $redis.expire(key, READONLY_MODE_KEY_TTL)
+            sleep 30.seconds
+          end
         end
       end
     end