introduce a timer class for reaping connections

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -64,6 +64,25 @@ module ConnectionAdapters
     # * +wait_timeout+: number of seconds to block and wait for a connection
     #   before giving up and raising a timeout error (default 5 seconds).
     class ConnectionPool
+      class Reaper
+        attr_reader :pool, :frequency
+
+        def initialize(pool, frequency)
+          @pool      = pool
+          @frequency = frequency
+        end
+
+        def start
+          return unless frequency
+          Thread.new(frequency, pool) { |t, p|
+            while true
+              sleep t
+              p.reap
+            end
+          }
+        end
+      end
+
       include MonitorMixin
 
       attr_accessor :automatic_reconnect, :timeout

activerecord/test/cases/reaper_test.rb

+require "cases/helper"
+
+module ActiveRecord
+  module ConnectionAdapters
+    class ReaperTest < ActiveRecord::TestCase
+      attr_reader :pool
+
+      def setup
+        super
+        @pool = ConnectionPool.new ActiveRecord::Base.connection_pool.spec
+      end
+
+      def teardown
+        super
+        @pool.connections.each(&:close)
+      end
+
+      # A reaper with nil time should never reap connections
+      def test_nil_time
+        conn = pool.checkout
+        pool.timeout = 0
+
+        count = pool.connections.length
+        conn.extend(Module.new { def active?; false; end; })
+
+        reaper = ConnectionPool::Reaper.new(pool, nil)
+        reaper.start
+        sleep 0.0001
+        assert_equal count, pool.connections.length
+      end
+
+      def test_some_time
+        conn = pool.checkout
+        pool.timeout = 0
+
+        count = pool.connections.length
+        conn.extend(Module.new { def active?; false; end; })
+
+        reaper = ConnectionPool::Reaper.new(pool, 0.0001)
+        reaper.start
+        sleep 0.0002
+        assert_equal(count - 1, pool.connections.length)
+      end
+    end
+  end
+end