Caching in development environment in Rails 5

Rails 5 adds a command for turning development caching on and off without editing config/environments/development.rb by hand. The command creates or removes tmp/caching-dev.txt, and the app uses that file to decide whether caching is enabled in development.

Reading notes

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• In Rails 4, enabling caching in development required changing configaction_controllerperform_caching in config/environments/development.rb and restarting the server.
• Rails 5 introduces rails dev:cache to help test caching behavior in development mode.
• Running rails dev:cache creates tmp/caching-dev.txt and prints that development mode is now being cached.
• In a new Rails 5 app, development.rb checks whether tmp/caching-dev.txt exists and then uses :mem_cache_store when it does.
• The dev cache code toggles the file in tmp/caching-dev.txt and touches tmp/restart.txt.
• The advantage is that caching can be turned on or off without restarting the server manually.
• The feature is not supported by unicorn, thin, and webrick.
• Running rails dev:cache again disables development caching if it was previously enabled.