patch.diff

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 f721e91203..746e0cf8c1 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -2,6 +2,7 @@
 
 require "thread"
 require "concurrent/map"
+require "concurrent/executor/timer_set"
 require "monitor"
 
 module ActiveRecord
@@ -285,30 +286,41 @@ def internal_poll(timeout)
       # Configure the frequency by setting +reaping_frequency+ in your database
       # yaml file (default 60 seconds).
       class Reaper
-        attr_reader :pool, :frequency
-
-        def initialize(pool, frequency)
-          @pool      = pool
-          @frequency = frequency
+        def initialize
+          @timer_set = Concurrent::TimerSet.new(
+            executor: Concurrent::FixedThreadPool.new(1)
+          )
         end
 
         def run
-          return unless frequency && frequency > 0
-          Thread.new(frequency, pool) { |t, p|
-            loop do
-              sleep t
-              p.reap
-              p.flush
-            end
-          }
+          Thread.new do
+            klass = ActiveRecord::ConnectionAdapters::ConnectionPool
+            ObjectSpace.each_object(klass) { |pool| queue_reaping(pool) }
+          end
         end
+
+        private
+
+          def queue_reaping(pool)
+            @timer_set.post(pool.reaping_frequency) do
+              if !pool.connections.empty?
+                pool.reap
+                pool.flush
+              end
+
+              queue_reaping(pool)
+            end
+          end
       end
 
       include MonitorMixin
       include QueryCache::ConnectionPoolConfiguration
 
       attr_accessor :automatic_reconnect, :checkout_timeout, :schema_cache
-      attr_reader :spec, :connections, :size, :reaper
+      attr_reader :spec, :connections, :size, :reaping_frequency
+
+      @@pools_to_reap = []
+      @@reaper = nil
 
       # Creates a new ConnectionPool object. +spec+ is a ConnectionSpecification
       # object which describes database connection information (e.g. adapter,
@@ -321,14 +333,12 @@ def initialize(spec)
 
         @spec = spec
 
-        @checkout_timeout = (spec.config[:checkout_timeout] && spec.config[:checkout_timeout].to_f) || 5
-        if @idle_timeout = spec.config.fetch(:idle_timeout, 300)
-          @idle_timeout = @idle_timeout.to_f
-          @idle_timeout = nil if @idle_timeout <= 0
-        end
+        @checkout_timeout = spec.config.fetch(:checkout_timeout, 5).to_f
+        @idle_timeout = spec.config.fetch(:idle_timeout, 300).to_f
+        @idle_timeout = nil if @idle_timeout <= 0
 
         # default max pool size to 5
-        @size = (spec.config[:pool] && spec.config[:pool].to_i) || 5
+        @size = spec.config.fetch(:pool, 5).to_i
 
         # This variable tracks the cache of threads mapped to reserved connections, with the
         # sole purpose of speeding up the +connection+ method. It is not the authoritative
@@ -358,9 +368,9 @@ def initialize(spec)
 
         # +reaping_frequency+ is configurable mostly for historical reasons, but it could
         # also be useful if someone wants a very low +idle_timeout+.
-        reaping_frequency = spec.config.fetch(:reaping_frequency, 60)
-        @reaper = Reaper.new(self, reaping_frequency && reaping_frequency.to_f)
-        @reaper.run
+        @reaping_frequency = spec.config.fetch(:reaping_frequency, 1).to_f
+        @@pools_to_reap << self if reaping_frequency > 0
+        @@reaper ||= Reaper.new.run
       end
 
       def lock_thread=(lock_thread)