Prior to this change, the first interaction with the database would emit the following deprecation warning with Rails 6.1:

DEPRECATION WARNING: connection_config is deprecated and will be removed from Rails 6.2 (Use connection_db_config instead)

The deprecation was introduced in rails/rails#38005 and includes the following release notes:

The connection_config method has been deprecated, please use connection_db_config instead which will return a DatabaseConfigurations::DatabaseConfig instead of a Hash.

Proposed resolution

With the changes in the pull request, Scout first attempts to use connection_db_config. If unsuccessful, Scout falls back to the previous behavior of using connection_config.

How to reproduce the deprecation warning

1. Verify you're using Rails 6.1:

   $ rails -v
   Rails 6.1.0
   

2. Set up a new Rails app with scout_apm:

   $ rails new sample --database=postgresql
   $ cd sample/
   $ rails db:create
   $ rails generate model User name:string
   $ rails db:migrate
   $ bundle add scout_apm 
   

3. Load Scout and interact with the database:

   $ SCOUT_DEV_TRACE=true rails console
   
   2.7.2-p137> User.count
   DEPRECATION WARNING: connection_config is deprecated and will be removed from Rails 6.2 (Use connection_db_config instead) (called from irb_binding at (irb):1)
     (0.4ms)  SELECT COUNT(*) FROM "users"
   => 0