Class: ConsistentRandom

Inherits:
Object
  • Object
show all
Defined in:
lib/consistent_random.rb,
lib/consistent_random/active_job.rb,
lib/consistent_random/rack_middleware.rb,
lib/consistent_random/sidekiq_middleware.rb,
lib/consistent_random/sidekiq_client_middleware.rb

Defined Under Namespace

Modules: ActiveJob Classes: RackMiddleware, SidekiqClientMiddleware, SidekiqMiddleware

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name) ⇒ ConsistentRandom

Returns a new instance of ConsistentRandom.

Parameters:

  • name (Object) —

    a name used to identifuy a consistent random value



57
58
59
 
# File 'lib/consistent_random.rb', line 57

def initialize(name)
  @name = name
end

Class Method Details

.current_seed ⇒ String?

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Get the current seed used to generate random numbers. This will return nil if called outside of a scope.

Returns:

  • (String, nil) —

    the seed value for the current scope or nil if called outside of a scope.



51
52
53
 
# File 'lib/consistent_random.rb', line 51

def current_seed
  Thread.current[:consistent_random_seed]
end

.scope(seed = nil) { ... } ⇒ Object

Define a scope where consistent random values will be generated.

Parameters:

  • seeds (String, Symbol, Integer, Array<String>, Array<Integer>, nil) —

    optional value to use for generating random numbers. By default a random value will be generated. If the scope is nested in another scope block, then the seed from the parent scope will be used by default.

Yields:

  • block of code to execute within the scope

Returns:

  • the result of the block



24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
 
# File 'lib/consistent_random.rb', line 24

def scope(seed = nil)
  existing_seed = Thread.current[:consistent_random_seed]
  seed_value = case seed
  when nil
    existing_seed || SecureRandom.hex
  when String, Symbol, Integer
    seed.to_s
  when Array
    seed.map { |s| s.to_s }.join("\x1C")
  else
    raise ArgumentError, "Invalid seed value: #{seed.inspect}"
  end

  begin
    Thread.current[:consistent_random_seed] = seed_value
    yield
  ensure
    Thread.current[:consistent_random_seed] = existing_seed
  end
end

Instance Method Details

#==(other) ⇒ Boolean

Returns true if the other object is a ConsistentRandom that returns the same random number generator. If called outside of a scope, then it will always return false.

Returns:

  • (Boolean) —

    true if the other object is a ConsistentRandom that returns the same random number generator. If called outside of a scope, then it will always return false.



105
106
107
 
# File 'lib/consistent_random.rb', line 105

def ==(other)
  other.is_a?(self.class) && other.seed == seed
end

#bytes(size) ⇒ String

Generate a random array of bytes. The same number will be generated within a scope block. This method works the same as Random#bytes.

Parameters:

  • size (Integer) —

    the number of bytes to generate.

Returns:

  • (String) —

    a string of random bytes.



87
88
89
90
91
 
# File 'lib/consistent_random.rb', line 87

def bytes(size)
  bytes = []
  ((size + 19) / 20).times { |i| bytes << seed_hash("#{@name}#{i}").to_s }
  bytes.join[0, size]
end

#rand(max = nil) ⇒ Numeric

Generate a random number. The same number will be generated within a scope block. This method works the same as Kernel#rand. It will generate a consistent value even across Ruby versions and platforms.

Parameters:

  • max (Integer, Range) (defaults to: nil) —

    the maximum value of the random float or a range indicating the minimum and maximum values.

Returns:

  • (Numeric) —

    a random number. If the max argument is a range, then the result will be a number in that range. If max is an number, then it will be an integer between 0 and that value. Otherwise, it will be a float between 0 and 1.



70
71
72
73
74
75
76
77
78
79
80
 
# File 'lib/consistent_random.rb', line 70

def rand(max = nil)
  value = seed / SEED_DIVISOR
  case max
  when nil
    value
  when Numeric
    (value * max.to_i).to_i
  when Range
    cap_to_range(value, max)
  end
end

#random ⇒ Random

Generate a random number generator for the given name. The generator will always have the same seed within a scope.

This value is dependent on the Ruby Random class and may not generate consistent values across Ruby versions and platforms.

Returns:

  • (Random) —

    a random number generator



116
117
118
 
# File 'lib/consistent_random.rb', line 116

def random
  Random.new(seed)
end

#seed ⇒ Integer

Generate a seed that can be used to generate random numbers. This seed will be return a consistent value when called within a scope.

Returns:

  • (Integer) —

    a 64 bit integer for seeding random values



97
98
99
100
 
# File 'lib/consistent_random.rb', line 97

def seed
  hash = seed_hash(@name)
  hash.byteslice(0, 8).unpack1("Q>")
end