Upgrade to Rails 6.0 and apply new framework defaults

config/environments/production.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 Rails.application.configure do
-  # Verifies that versions and hashed value of the package contents in the project's package.json
-  config.webpacker.check_yarn_integrity = false
   # Settings specified here will take precedence over those in config/application.rb.
 
   # Code is not reloaded between requests.
@@ -27,20 +25,13 @@ Rails.application.configure do
   # Apache or NGINX already handles this.
   config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?
 
-  # Compress JavaScripts and CSS.
+  # Compress JavaScript and CSS using a preprocessor.
   config.assets.js_compressor = Uglifier.new(harmony: true)
-  # config.assets.js_compressor = :uglifier
   # config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.
   config.assets.compile = false
 
-  # Asset digests allow you to set far-future HTTP expiration dates on all assets,
-  # yet still be able to expire them through the digest params.
-  config.assets.digest = true
-
-  # `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'
 
@@ -48,10 +39,10 @@ Rails.application.configure do
   # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache
   # config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX
 
-  # Store uploaded files on the local file system (see config/storage.yml for options)
+  # Store uploaded files on the local file system (see config/storage.yml for options).
   config.active_storage.service = :local
 
-  # Mount Action Cable outside main process or domain
+  # Mount Action Cable outside main process or domain.
   # config.action_cable.mount_path = nil
   # config.action_cable.url = 'wss://example.com/cable'
   # config.action_cable.allowed_request_origins = [ 'http://example.com', /http:\/\/example.*/ ]
@@ -69,9 +60,9 @@ Rails.application.configure do
   # 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 = "code_ocean_#{Rails.env}"
+  # config.active_job.queue_name_prefix = "code_ocean_production"
 
   config.action_mailer.perform_caching = false
 
@@ -101,4 +92,25 @@ Rails.application.configure do
 
   # 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