--- a/config/environments/production.rb	Fri May 31 09:10:37 2019 +0900
+++ b/config/environments/production.rb	Tue Oct 22 16:17:30 2019 +0900
@@ -14,19 +14,20 @@
   config.consider_all_requests_local       = false
   config.action_controller.perform_caching = true
 
+  # Ensures that a master key has been made available in either ENV["RAILS_MASTER_KEY"]
+  # or in config/master.key. This key is used to decrypt credentials (and other encrypted files).
+  # config.require_master_key = true
+
   # Disable serving static files from the `/public` folder by default since
   # Apache or NGINX already handles this.
-  config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
+  config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?
 
-  # Compress JavaScripts and CSS.
-  config.assets.js_compressor = :uglifier
+  # Compress CSS using a preprocessor.
   # config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.
   config.assets.compile = false
 
-  # `config.assets.precompile` and `config.assets.version` have moved to config/initializers/assets.rb
-
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.action_controller.asset_host = 'http://assets.example.com'
 
@@ -34,13 +35,6 @@
   # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache
   # config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX
 
-  # Action Cable endpoint configuration
-  # config.action_cable.url = 'wss://example.com/cable'
-  # config.action_cable.allowed_request_origins = [ 'http://example.com', /http:\/\/example.*/ ]
-
-  # Don't mount Action Cable in the main server process.
-  # config.action_cable.mount_path = nil
-
   # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
   # config.force_ssl = true
 
@@ -49,19 +43,14 @@
   config.log_level = :debug
 
   # Prepend all log lines with the following tags.
-  config.log_tags = [:request_id]
+  config.log_tags = [ :request_id ]
 
   # Use a different cache store in production.
   # config.cache_store = :mem_cache_store
 
-  # Use a real queuing backend for Active Job (and separate queues per environment)
+  # Use a real queuing backend for Active Job (and separate queues per environment).
   # config.active_job.queue_adapter     = :resque
-  # config.active_job.queue_name_prefix = "zeropaste_#{Rails.env}"
-  # config.action_mailer.perform_caching = false
-
-  # Ignore bad email addresses and do not raise email delivery errors.
-  # Set this to true and configure the email server for immediate delivery to raise delivery errors.
-  # config.action_mailer.raise_delivery_errors = false
+  # config.active_job.queue_name_prefix = "zeropaste_production"
 
   # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
   # the I18n.default_locale when a translation cannot be found).
@@ -78,11 +67,32 @@
   # config.logger = ActiveSupport::TaggedLogging.new(Syslog::Logger.new 'app-name')
 
   if $cfg[:log_to_stdout]
-    logger = ActiveSupport::Logger.new(STDOUT)
+    logger           = ActiveSupport::Logger.new(STDOUT)
     logger.formatter = config.log_formatter
-    config.logger = ActiveSupport::TaggedLogging.new(logger)
+    config.logger    = ActiveSupport::TaggedLogging.new(logger)
   end
 
   # Do not dump schema after migrations.
   config.active_record.dump_schema_after_migration = false
+
+  # Inserts middleware to perform automatic connection switching.
+  # The `database_selector` hash is used to pass options to the DatabaseSelector
+  # middleware. The `delay` is used to determine how long to wait after a write
+  # to send a subsequent read to the primary.
+  #
+  # The `database_resolver` class is used by the middleware to determine which
+  # database is appropriate to use based on the time delay.
+  #
+  # The `database_resolver_context` class is used by the middleware to set
+  # timestamps for the last write to the primary. The resolver uses the context
+  # class timestamps to determine how long to wait before reading from the
+  # replica.
+  #
+  # By default Rails will store a last write timestamp in the session. The
+  # DatabaseSelector middleware is designed as such you can define your own
+  # strategy for connection switching and pass that into the middleware through
+  # these configuration options.
+  # config.active_record.database_selector = { delay: 2.seconds }
+  # config.active_record.database_resolver = ActiveRecord::Middleware::DatabaseSelector::Resolver
+  # config.active_record.database_resolver_context = ActiveRecord::Middleware::DatabaseSelector::Resolver::Session
 end