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Caching library to simplify and organize caching.

  • I18n (seperate caches by locale / expires all locales)
  • Generation based (your able expire all caches of one type)
  • Simultanouse caching (handle multiple processes trying to write same expensive cache at once)
  • Dependent caches (x caches result of cache z+y -> z changes -> x changes)
  • Hashed keys (optional -> short/unreadable)
  • Global cache_version (expire everything Cachy cached, but not e.g. sessions)
  • ...
  • works out of the box with Rails
  • works with pure Memcache, Redis and Moneta(-> Tokyo Cabinet / CouchDB / S3 / Berkeley DB / DataMapper / Memory store)


As Gem: sudo gem install cachy Or as Rails plugin: script/plugins install git://



result = Cachy.cache(:a_key){ expensive() }
result = Cachy.cache(:a_key, :expires_in => 1.minute){ expensive() }
result = Cachy.cache(:a_key, 'something else',{ expensive() }

Cache expensive operation that is run many times by many processes

Example: at application startup 20 processes try to set the same cache -> 20 heavy database requests -> database timeout -> cache still empty -> ... -> death

# 19 Processes get [], 1 makes the request -- when cached all get the same result
result = Cachy.cache(:a_key, :while_running=>[]){ block_db_for_5_seconds }

Seperate version for each key

Expire all all caches of one kind when code inside the cache has been updated

100.times{ Cachy.cache(:a_key, rand(100000) ){ expensive() } }
Cachy.increment_key(:a_key) --> everything expired

Uses I18n.locale if available

Cachy.cache(:a_key){ 'English' }
I18n.locale = :de
Cachy.cache(:a_key){ 'German' } != 'English'

Explicitly not use I18n.locale

Cachy.cache(:a_key, :witout_locale=>true){ 'English' }
I18n.locale = :de
Cachy.cache(:a_key, :witout_locale=>true){ 'German' } == 'English'

Caching results of other caches

When inner cache is expired outer cache would normally still shows old results.
--> expire outer cache when inner cache is expired.

a = Cachy.cache(:a, :expires_in=>{ expensive() }
b = Cachy.cache(:b, :expires_in=>1.week){ expensive_2() }
Cachy.cache(:surrounding, :expires_in=>5.hours, :keys=>[:a, :b]){ a + b * c }
Cachy.increment_key(:b) -->  expires :b and :surrounding

Hashing keys

In case they get to long for your caching backend, makes them short but unreadable.

Cachy.hash_keys = true  # global
Cachy.cache(:a_key, :hash_key=>true){ expensive } # per call

Uses .cache_key when available

E.g. ActiveRecord objects are stored in the key with their updated_at timestamp.
When they are updated the cache is automatically expired.

Cachy.cache(:my_key, User.first){ expensive }

Uses CACHE_VERSION if defined

Use a global CACHE_VERSION=1 so that all caches can be expired when something big changes. The cache server does not need to be restarted and session data(Rails) is saved.

Does not cache nil

If you want to cache a falsy result, use false (same goes for :while_running) Cachy.cache(:x){ expensive || false } Cachy.cache(:x, :while_running=>false){ expensive }


Only caches if condition is fulfilled Cachy.cache_if(condition, :foo, 'bar', :expires_in => 1.minute){do_something}

Cachy.expire / .expire_view

Expires all locales of a key Cachy.locales = [:de, :en] # by default filled with I18n.available_locales Cachy.expire(:my_key) -> expires for :de, :en and no-locale

#expire "views/#{key}" (counterpart for Rails-view-caching)
Cachy.expire(:my_key, :prefix=>'views/')


Use to cache e.g. Erb output <% cache Cachy.key(:a_key), :expires_in=>1.hour do %> More html ... <% end %>


No ActionController::Base.cache_store ?
Give me something that responds to read/write(Rails style) or []/store(Moneta) or get/set(Memcached) Cachy.cache_store = some_cache


No I18n.available_locales ? Cachy.locales = [:de, :en, :fr]

Memcache timeout protection

If Memcache timeouts keep killing your pages -> catch MemCache timeouts


  • optionally store dependent keys (:keys=>xxx), so that they can be setup up once and do not need to be remembered



Michael Grosser
Hereby placed under public domain, do what you want, just do not hold me accountable...

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