Add Inspect Configuration Of Database Connection as a Rails TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1568 TILs and counting..._
+_1569 TILs and counting..._
 
 See some of the other learning resources I work on:
 - [Ruby Operator Lookup](https://www.visualmode.dev/ruby-operators)
@@ -1009,6 +1009,7 @@ See some of the other learning resources I work on:
 - [Hash Slicing](rails/hash-slicing.md)
 - [Ignore Poltergeist JavaScript Errors](rails/ignore-poltergeist-javascript-errors.md)
 - [Include Devise Helpers In Your Controller Tests](rails/include-devise-helpers-in-your-controller-tests.md)
+- [Inspect Configuration Of Database Connection](rails/inspect-configuration-of-database-connection.md)
 - [Inspect Previous Changes To ActiveRecord Object](rails/inspect-previous-changes-to-activerecord-object.md)
 - [Link To The Current Page With Query Params](rails/link-to-the-current-page-with-query-params.md)
 - [List All Installable Rails Versions](rails/list-all-installable-rails-versions.md)

rails/inspect-configuration-of-database-connection.md

@@ -0,0 +1,45 @@
+# Inspect Configuration Of Database Connection
+
+There are a lot of factors that can effect the database configuration values.
+
+- What are the settings in each environment in `config/database.yml`?
+- Is there any dynamic ERB code in `config/database.yml`?
+- Is `DATABASE_URL` set in the current environment?
+- Is any other code overriding these settings?
+
+To check the current _configuration hash_ for the database connection at
+runtime, we can run the following statement:
+
+```ruby
+> ActiveRecord::Base.connection.pool.db_config.configuration_hash
+=>
+{:adapter=>"postgresql",
+ :encoding=>"unicode",
+ :host=>"::1",
+ :user=>"postgres",
+ :password=>"postgres",
+ :pool=>5,
+ :database=>"still_development",
+ :port=>9875}
+```
+
+In this case, I'm running the statement from the Rails console of my app's
+development environment.
+
+I could even access and print these values as part of debugging in a production
+environment with a rake task:
+
+```ruby
+# In lib/tasks/debug.rake
+namespace :debug do
+  task :db_config => :environment do
+    puts "==== Database Configuration Debug ===="
+    puts "DATABASE_URL: #{ENV['DATABASE_URL']}"
+    puts "Active Record Config: #{ActiveRecord::Base.connection.pool.db_config.configuration_hash}"
+    puts "Raw ENV dump:"
+    ENV.sort.each { |k,v| puts "#{k}: #{v}" if k.include?('DB') || k.include?('DATABASE') }
+  end
+end
+```
+
+[source](https://api.rubyonrails.org/classes/ActiveRecord/DatabaseConfigurations/HashConfig.html)