我在Ubuntu 14.04上运行Rails 4.2.7，我编写了以下方法来帮助缓存一些数据（防止对我的PostGres 9.5数据库的命中）...

class Country < ActiveRecord::Base
  has_many :states

  def self.cached_find_by_iso(iso)
    Rails.cache.fetch("#{iso}") do
      find_by_iso(iso)
    end
  end

end

然而，即使在运行rake tmp：cache：clear并重新启动我的服务器之后，我在尝试调用上面的命令时还是会收到这个错误。

Error during processing: Not a directory @ rb_file_s_rename - (/home/rails/myproject/tmp/cache/00020161104-1093-67j634, /home/rails/myproject/tmp/cache/001/000/)
/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/fileutils.rb:528:in `rename'
/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/fileutils.rb:528:in `block in mv'
/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/fileutils.rb:1571:in `block in fu_each_src_dest'
/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/fileutils.rb:1587:in `fu_each_src_dest0'
/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/fileutils.rb:1569:in `fu_each_src_dest'
/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/fileutils.rb:517:in `mv'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/core_ext/file/atomic.rb:36:in `atomic_write'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache/file_store.rb:83:in `write_entry'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache/strategy/local_cache.rb:115:in `write_entry'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache.rb:391:in `block in write'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache.rb:547:in `block in instrument'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/notifications.rb:166:in `instrument'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache.rb:547:in `instrument'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache.rb:389:in `write'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache.rb:588:in `save_block_result_to_cache'
/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.7.1/lib/active_support/cache.rb:299:in `fetch'
/home/rails/myproject/app/models/country.rb:5:in `cached_find_by_iso'
/home/rails/myproject/app/services/all_events_guide_service.rb:84:in `block in process_page_data'
/usr/local/rvm/gems/ruby-2.3.0/gems/nokogiri-1.6.8.1/lib/nokogiri/xml/node_set.rb:187:in `block in each'
/usr/local/rvm/gems/ruby-2.3.0/gems/nokogiri-1.6.8.1/lib/nokogiri/xml/node_set.rb:186:in `upto'
/usr/local/rvm/gems/ruby-2.3.0/gems/nokogiri-1.6.8.1/lib/nokogiri/xml/node_set.rb:186:in `each'
/home/rails/myproject/app/services/all_events_guide_service.rb:45:in `process_page_data'
/home/rails/myproject/app/services/abstract_import_service.rb:83:in `process_my_object_data'
/home/rails/myproject/app/services/all_events_guide_my_object_finder_service.rb:103:in `block in process_my_object_link'
/usr/local/rvm/gems/ruby-2.3.0/gems/nokogiri-1.6.8.1/lib/nokogiri/xml/node_set.rb:187:in `block in each'
/usr/local/rvm/gems/ruby-2.3.0/gems/nokogiri-1.6.8.1/lib/nokogiri/xml/node_set.rb:186:in `upto'
/usr/local/rvm/gems/ruby-2.3.0/gems/nokogiri-1.6.8.1/lib/nokogiri/xml/node_set.rb:186:in `each'
/home/rails/myproject/app/services/all_events_guide_my_object_finder_service.rb:82:in `process_my_object_link'
/home/rails/myproject/app/services/abstract_my_object_finder_service.rb:29:in `block in process_data'
/home/rails/myproject/app/services/abstract_my_object_finder_service.rb:28:in `each'
/home/rails/myproject/app/services/abstract_my_object_finder_service.rb:28:in `process_data'
/home/rails/myproject/app/services/run_crawlers_service.rb:18:in `block in run_all_crawlers'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/relation/delegation.rb:46:in `each'
/usr/local/rvm/gems/ruby-2.3.0/gems/activerecord-4.2.7.1/lib/active_record/relation/delegation.rb:46:in `each'
/home/rails/myproject/app/services/run_crawlers_service.rb:5:in `run_all_crawlers'
/home/rails/myproject/app/controllers/my_objects_controller.rb:170:in `block in import'

清除缓存并允许缓存的方法正常开始工作的正确方法是什么？

**编辑：**Deepak的建议也有同样的错误，但下面是他的答案的输出...

rails@mymachine:~/myproject$ rails console
Loading development environment (Rails 4.2.7.1)
2.3.0 :001 > Rails.cache.clear
 => ["/home/rails/myproject/tmp/cache/assets"] 
2.3.0 :002 > quit

**编辑2：**这是我的config/environments.production.rb文件。这是一个生产环境...

Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.

  # Code is not reloaded between requests.
  config.cache_classes = true

  # Eager load code on boot. This eager loads most of Rails and
  # your application in memory, allowing both threaded web servers
  # and those relying on copy on write to perform better.
  # Rake tasks automatically ignore this option for performance.
  config.eager_load = true

  # Full error reports are disabled and caching is turned on.
  config.consider_all_requests_local       = false
  config.action_controller.perform_caching = true

  # Enable Rack::Cache to put a simple HTTP cache in front of your application
  # Add `rack-cache` to your Gemfile before enabling this.
  # For large-scale production use, consider using a caching reverse proxy like
  # NGINX, varnish or squid.
  # config.action_dispatch.rack_cache = true

  # Disable serving static files from the `/public` folder by default since
  # Apache or NGINX already handles this.
  config.serve_static_files = ENV['RAILS_SERVE_STATIC_FILES'].present?

  # Compress JavaScripts and CSS.
  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

  # Specifies the header that your server uses for sending files.
  # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache
  # config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX

  # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
  # config.force_ssl = true

  # Use the lowest log level to ensure availability of diagnostic information
  # when problems arise.
  config.log_level = :debug

  # Prepend all log lines with the following tags.
  # config.log_tags = [ :subdomain, :uuid ]

  # Use a different logger for distributed setups.
  # config.logger = ActiveSupport::TaggedLogging.new(SyslogLogger.new)

  # Use a different cache store in production.
  # config.cache_store = :mem_cache_store

  # Enable serving of images, stylesheets, and JavaScripts from an asset server.
  # config.action_controller.asset_host = 'http://assets.example.com'

  # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
  # the I18n.default_locale when a translation cannot be found).
  config.i18n.fallbacks = true

  # Send deprecation notices to registered listeners.
  config.active_support.deprecation = :notify

  # Use default logging formatter so that PID and timestamp are not suppressed.
  config.log_formatter = ::Logger::Formatter.new

  # Do not dump schema after migrations.
  config.active_record.dump_schema_after_migration = false

  config.serve_static_assets = true
  config.assets.compile = true
end