Clear active connections after initialization

Any connections that were checked out during initialization should be
checked back in before the first request is processed, for two reasons:

 - Returning the connection to the pool allows it to be health checked
   before it's used again. If the connection dies before the first
   request arrives, the health check will replace it with a new one.

 - If the thread that initialized Rails is not the same thread that will
   be performing work, checking in the connection will allow it to be
   reused instead of being stuck to the initialization thread forever.

1 files changed, 8 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 0276d41494..73518ca144 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -166,5 +166,13 @@ end_warning
       path = app.paths["db"].first
       config.watchable_files.concat ["#{path}/schema.rb", "#{path}/structure.sql"]
     end
+
+    initializer "active_record.clear_active_connections" do
+      config.after_initialize do
+        ActiveSupport.on_load(:active_record) do
+          clear_active_connections!
+        end
+      end
+    end
   end
 end