caches
caches
is a Ruby gem, providing a small collection of caches with good performance and hash-like access patterns. Each is named for its cache expiration strategy - when it will drop a key.
Usage
caches
provides the following classes.
Caches::TTL
TTL (Time To Live) remembers values for as many seconds as you tell it. The default is 3600 seconds (1 hour). Sub-seconds are supported; the tests will fail if the value is too low for your machine.
require 'caches/ttl'
h = Caches::TTL.new(ttl: 0.01)
h[:a] = 'aardvark'
h[:a] #=> 'aardvark'
sleep(0.02)
h[:a] #=> nil
Initialization Options
- With
refresh: true
, reading a value will reset its timer; otherwise, only writing will. - With
max_keys: 5
, on insertion, it will evict the oldest item if necessary to keep from exceeding 5 keys.
Methods
keys
and values
work the same as for a hash. They do not check whether each key is current.
memoize
method fetches a key if it exists and isn't expired; otherwise, it calculates the value using the block and saves it.
h = Caches::TTL.new(ttl: 5)
# Runs the block
h.memoize(:a) { |k| calculation_for(k) }
# Returns the previously-calculated value
h.memoize(:a) { |k| calculation_for(k) }
sleep(6)
# Runs the block
h.memoize(:a) { |k| calculation_for(k) }
Caches::LRU
LRU (Least Recently Used) remembers as many keys as you tell it to, dropping the least recently used key on each insert after its limit is reached. (Inserts and reads count as a usage; updates do not.)
require 'caches/lru'
h = Caches::LRU.new(max_keys: 3)
h[:a] = "aardvark"
h[:b] = "boron"
h[:c] = "cattail"
h[:d] = "dingo"
puts h[:a] # => nil
Installation
Add this line to your application's Gemfile:
gem 'caches'
And then execute:
$ bundle
Or install it yourself as:
$ gem install caches
Contributing
See CONTRIBUTING.md
Thanks
- Thanks to FromAToB.com for giving me time to make this
- Thanks to satyap; the original specs for
caches
were adapted from volatile_hash.