Class: Zache

Inherits:
Object
  • Object
show all
Defined in:
lib/zache.rb

Overview

It is a very simple thread-safe in-memory cache with an ability to expire keys automatically, when their lifetime is over. Use it like this:

require 'zache'
zache = Zache.new
# Expires in 5 minutes
v = zache.get(:count, lifetime: 5 * 60) { expensive() }

For more information read README file.

Author

Yegor Bugayenko ([email protected])

Copyright

Copyright © 2018 Yegor Bugayenko

License

MIT

Defined Under Namespace

Classes: Fake

Instance Method Summary collapse

Constructor Details

#initialize(sync: true, dirty: false) ⇒ Zache

Makes a new object of the cache. “sync” is whether the hash is thread-safe (`true`) or not (`false`); it is recommended to leave this parameter untouched, unless you really know what you are doing.

If the dirty argument is set to true, a previously calculated result will be returned if it exists and is already expired.


76
77
78
79
80
81
 
# File 'lib/zache.rb', line 76

def initialize(sync: true, dirty: false)
  @hash = {}
  @sync = sync
  @dirty = dirty
  @mutex = Mutex.new
end

Instance Method Details

#clean ⇒ Object

Remove keys that are expired.


153
154
155
 
# File 'lib/zache.rb', line 153

def clean
  synchronized { @hash.delete_if { |_key, value| key_expired?(value) } }
end

#exists?(key) ⇒ Boolean

Checks whether the value exists in the cache by the provided key. Returns TRUE if the value is here. If the key is already expired in the hash, it will be removed by this method and the result will be FALSE.

Returns:

  • (Boolean) 

116
117
118
119
120
121
122
123
 
# File 'lib/zache.rb', line 116

def exists?(key)
  rec = @hash[key]
  if key_expired?(key)
    @hash.delete(key)
    rec = nil
  end
  !rec.nil?
end

#get(key, lifetime: 2**32, dirty: false) ⇒ Object

Gets the value from the cache by the provided key. If the value is not found in the cache, it will be calculated via the provided block. If the block is not given, an exception will be raised. The lifetime must be in seconds. The default lifetime is huge, which means that the key will never be expired.

If the dirty argument is set to true, a previously calculated result will be returned if it exists and is already expired.


96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
 
# File 'lib/zache.rb', line 96

def get(key, lifetime: 2**32, dirty: false)
  if block_given?
    if (dirty || @dirty) && locked? && key_expired?(key) && @hash.key?(key)
      return @hash[key][:value]
    end
    synchronized { calc(key, lifetime) { yield } }
  else
    rec = @hash[key]
    if key_expired?(key)
      @hash.delete(key)
      rec = nil
    end
    raise 'The key is absent in the cache' if rec.nil?
    rec[:value]
  end
end

#locked? ⇒ Boolean

Is cache currently locked doing something?

Returns:

  • (Boolean) 

126
127
128
 
# File 'lib/zache.rb', line 126

def locked?
  @mutex.locked?
end

#put(key, value, lifetime: 2**32) ⇒ Object

Put a value into the cache.


131
132
133
134
135
136
137
138
139
 
# File 'lib/zache.rb', line 131

def put(key, value, lifetime: 2**32)
  synchronized do
    @hash[key] = {
      value: value,
      start: Time.now,
      lifetime: lifetime
    }
  end
end

#remove(key) ⇒ Object

Removes the value from the hash, by the provied key. If the key is absent and the block is provide, the block will be called.


143
144
145
 
# File 'lib/zache.rb', line 143

def remove(key)
  synchronized { @hash.delete(key) { yield if block_given? } }
end

#remove_all ⇒ Object

Remove all keys from the cache.


148
149
150
 
# File 'lib/zache.rb', line 148

def remove_all
  synchronized { @hash = {} }
end

#size ⇒ Object

Total number of keys currently in cache.


84
85
86
 
# File 'lib/zache.rb', line 84

def size
  @hash.size
end