MemoryCache

Cache the result of a ruby block within the ruby process for a finite period. Useful when you want to cache a few things, but don't want to bother with setting up a separate caching service like memcached.

Example:

# In an initializer
JsonCache = MemoryCache.new(minutes: 5)

# In your code
JsonCache.get(url) do
  raw_json = open(url).read
  JSON.parse(raw_json)
end

The block will be invoked the first time, but any subsequent calls to getin the next 5 minutes will ignore the block and just return the same value as the first invocation did.

Add this line to your application's Gemfile:

gem 'memory_cache'

And then execute:

$ bundle

Or install it yourself as:

$ gem install memory_cache

Load the gem and create a cache. Specify the cache duration through the initializer. seconds, minutes, hours and days are valid options.

cache = MemoryCache.new(minutes: 2, seconds: 30)

This creates a cache where objects expire after 150 seconds.

If you fail to provide any of the above keys, the initializer will raise an ArgumentError.

Unlike other cache libraries, memory_cache doesn't have a set method. Instead the get method also acts as a set method by passing a block.

cache.get('the_game')
=> nil
cache.get('the_game') { "you just lost it".upcase }
=> "YOU JUST LOST IT"
cache.get('the_game')
=> "YOU JUST LOST IT"

# 2 minutes and 31 seconds later
cache.get('the_game')
=> nil

MemoryCache does nothing to clean up the cache. Expired values will remain the internal hash of MemoryCache until they are replaced by new invocation with a block.

If your key set is massive or your block return values are fatty, consider calling clear on the cache now and then or go for a more advanced caching solution.