LRU cache

💎 Key/value LRU cache that supports lifecycle, global size limit and expiration time.

LRU: Least Recently Used

lru-cache supports lifecycle, a global item size limit and an expiration time can be set for each item independently.

If a max_size is defined, the LRU cache can only contain max_size items. Beyond max_size, items are deleted from the oldest to the most recently used.

A caching system is a vital part, it must be simple to use, reliable and efficient. lru-cache is battle tested 👌

Installation

Add the dependency to your shard.yml:

   dependencies:
     lru-cache:
       github: nicolab/crystal-lru-cache
       version: ~> 1.0.3 # Check the latest version!

Run shards install

Usage

require "lru-cache"

cache = LRUCache(String, String).new(max_size: 10_000)

cache.set("hello", "Hello Crystal!")
puts cache.get("hello") # => "Hello Crystal!"

# or
puts cache["hello"] # => "Hello Crystal!"

puts cache.has?("hello") # => true

# Time limit
cache.set("hello", "Hello Crystal!", Time.utc + 1.hour)

puts cache.expire_at "hello" # => Time.utc + 1.hour

# Deletes "hello" item
cache.delete "hello"

# Empties the cache
cache.clear

Lifecycle:

require "lru-cache"

class Cache(K, V) < LRUCache(K, V)
  # Optional lifecycle method to be executed after setting an item (`add!` and `set`).
  private def after_set(key : K, item : Tuple(V, Time?))
    puts "after_set: #{key}"
    pp item
  end

  # Optional lifecycle method to be executed after deleting an item (`delete`).
  private def after_delete(key : K, item : Tuple(V, Time?)?)
    puts "after_delete: #{key}"
    pp item
  end

  # Optional lifecycle method to be executed after clearing all the cache (`clear`).
  private def after_clear
    puts "after_clear"
  end
end

cache = Cache(String, String).new(max_size: 10_000)

cache.set("hello", "Hello Crystal!")
cache.set("foo", "bar")
cache.delete("foo")
cache.clear