class LaunchDarkly::ExpiringCache

A thread-safe cache with maximum number of entries and TTL. Adapted from github.com/SamSaffron/lru_redux/blob/master/lib/lru_redux/ttl/cache.rb under MIT license with the following changes:

* made thread-safe
* removed many unused methods
* reading a key does not reset its expiration time, only writing

@private

Public Class Methods

new(max_size, ttl) click to toggle source
# File lib/ldclient-rb/expiring_cache.rb, line 11
def initialize(max_size, ttl)
  @max_size = max_size
  @ttl = ttl
  @data_lru = {}
  @data_ttl = {}
  @lock = Mutex.new
end

Public Instance Methods

[](key) click to toggle source
# File lib/ldclient-rb/expiring_cache.rb, line 19
def [](key)
  @lock.synchronize do
    ttl_evict
    @data_lru[key]
  end
end
[]=(key, val) click to toggle source
# File lib/ldclient-rb/expiring_cache.rb, line 26
def []=(key, val)
  @lock.synchronize do
    ttl_evict

    @data_lru.delete(key)
    @data_ttl.delete(key)

    @data_lru[key] = val
    @data_ttl[key] = Time.now.to_f

    if @data_lru.size > @max_size
      key, _ = @data_lru.first # hashes have a FIFO ordering in Ruby

      @data_ttl.delete(key)
      @data_lru.delete(key)
    end

    val
  end
end
clear() click to toggle source
# File lib/ldclient-rb/expiring_cache.rb, line 56
def clear
  @lock.synchronize do
    @data_lru.clear
    @data_ttl.clear
  end
end
delete(key) click to toggle source
# File lib/ldclient-rb/expiring_cache.rb, line 47
def delete(key)
  @lock.synchronize do
    ttl_evict

    @data_lru.delete(key)
    @data_ttl.delete(key)
  end
end

Private Instance Methods

ttl_evict() click to toggle source
# File lib/ldclient-rb/expiring_cache.rb, line 65
def ttl_evict
  ttl_horizon = Time.now.to_f - @ttl
  key, time = @data_ttl.first

  until time.nil? || time > ttl_horizon
    @data_ttl.delete(key)
    @data_lru.delete(key)

    key, time = @data_ttl.first
  end
end