From 3e2e8eeb9ea552bd4782538cf9348455f3d0e14a Mon Sep 17 00:00:00 2001
From: John Hawthorn <john@hawthorn.email>
Date: Fri, 17 May 2019 09:44:06 -0700
Subject: Use a single thread for all ConnectionPool Reapers

Previously we would spawn one thread per connection pool, which ends up
being wasteful for apps with several connection pools.
---
 .../abstract/connection_pool.rb                    | 32 +++++++++++++++++-----
 1 file changed, 25 insertions(+), 7 deletions(-)

(limited to 'activerecord')

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index 68498b5dc5..4ff3cb0071 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -294,15 +294,33 @@ module ActiveRecord
           @frequency = frequency
         end
 
+        @@mutex = Mutex.new
+        @@pools = {}
+
+        def self.register_pool(pool, frequency) # :nodoc:
+          @@mutex.synchronize do
+            if @@pools.key?(frequency)
+              @@pools[frequency] << pool
+            else
+              @@pools[frequency] = [pool]
+              Thread.new(frequency) do |t|
+                loop do
+                  sleep t
+                  @@mutex.synchronize do
+                    @@pools[frequency].each do |p|
+                      p.reap
+                      p.flush
+                    end
+                  end
+                end
+              end
+            end
+          end
+        end
+
         def run
           return unless frequency && frequency > 0
-          Thread.new(frequency, pool) { |t, p|
-            loop do
-              sleep t
-              p.reap
-              p.flush
-            end
-          }
+          self.class.register_pool(pool, frequency)
         end
       end
 
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