FIX: pool drainer to use Rails 5.2 implementation

old implementation did not reap abandoned connections

lib/freedom_patches/pool_drainer.rb

@@ -25,31 +25,23 @@ class ActiveRecord::ConnectionAdapters::ConnectionPool
   # drain all idle connections
   # if idle_time is specified only connections idle for N seconds will be drained
   def drain(idle_time = nil, max_age = nil)
-    synchronize do
-      if @available && @connections
-        @available.clear
-        @connections.delete_if do |conn|
-          try_drain?(conn, idle_time, max_age)
-        end
+    return if !(@connections && @available)
 
-        @connections.each do |conn|
-          @available.add conn if !conn.in_use?
-        end
+    idle_connections = synchronize do
+      @connections.select do |conn|
+        !conn.in_use? && ((idle_time && conn.last_use <= idle_time.seconds.ago) || (max_age && conn.first_use < max_age.seconds.ago))
+      end.each do |conn|
+        conn.lease
+
+        @available.delete conn
+        @connections.delete conn
       end
     end
 
+    idle_connections.each do |conn|
+      conn.disconnect!
+    end
+
   end
 
-  private
-
-  def try_drain?(conn, idle_time, max_age)
-    if !conn.in_use?
-      if !idle_time || conn.last_use < idle_time.seconds.ago || (max_age && conn.first_use < max_age.seconds.ago)
-        conn.disconnect!
-        return true
-      end
-    end
-
-    false
-  end
 end