Class: Datadog::Tracing::Sampling::TokenBucket

Inherits:
RateLimiter
  • Object
show all
Defined in:
lib/datadog/tracing/sampling/rate_limiter.rb

Overview

Implementation of the Token Bucket metering algorithm for rate limiting.

See Also:

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(rate, max_tokens = rate) ⇒ TokenBucket

Returns a new instance of TokenBucket.

Raises:

  • (ArgumentError) 


37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
 
# File 'lib/datadog/tracing/sampling/rate_limiter.rb', line 37

def initialize(rate, max_tokens = rate)
  super()

  raise ArgumentError, "rate must be a number: #{rate}" unless rate.is_a?(Numeric)
  raise ArgumentError, "max_tokens must be a number: #{max_tokens}" unless max_tokens.is_a?(Numeric)

  @rate = rate
  @max_tokens = max_tokens

  @tokens = max_tokens
  @total_messages = 0
  @conforming_messages = 0
  @prev_conforming_messages = nil
  @prev_total_messages = nil
  @current_window = nil

  @last_refill = Core::Utils::Time.get_time
end

Instance Attribute Details

#max_tokens ⇒ Object (readonly)

Returns the value of attribute max_tokens.



31
32
33
 
# File 'lib/datadog/tracing/sampling/rate_limiter.rb', line 31

def max_tokens
  @max_tokens
end

#rate ⇒ Object (readonly)

Returns the value of attribute rate.



31
32
33
 
# File 'lib/datadog/tracing/sampling/rate_limiter.rb', line 31

def rate
  @rate
end

Instance Method Details

#allow?(size) ⇒ Boolean

Checks if a message of provided size conforms with the current bucket limit.

If it does, return true and remove size tokens from the bucket. If it does not, return false without affecting the tokens from the bucket.



65
66
67
68
69
 
# File 'lib/datadog/tracing/sampling/rate_limiter.rb', line 65

def allow?(size)
  allowed = should_allow?(size)
  update_rate_counts(allowed)
  allowed
end

#available_tokens ⇒ Numeric 



99
100
101
 
# File 'lib/datadog/tracing/sampling/rate_limiter.rb', line 99

def available_tokens
  @tokens
end

#current_window_rate ⇒ Float

Ratio of ‘conformance’ per ‘total messages’ checked on this bucket

Returns 1.0 when no messages have been checked yet.



92
93
94
95
96
 
# File 'lib/datadog/tracing/sampling/rate_limiter.rb', line 92

def current_window_rate
  return 1.0 if @total_messages.zero?

  @conforming_messages.to_f / @total_messages
end

#effective_rate ⇒ Float

Ratio of ‘conformance’ per ‘total messages’ checked averaged for the past 2 buckets

Returns 1.0 when no messages have been checked yet.



77
78
79
80
81
82
83
84
 
# File 'lib/datadog/tracing/sampling/rate_limiter.rb', line 77

def effective_rate
  return 0.0 if @rate.zero?
  return 1.0 if @rate < 0 || @total_messages.zero?

  return current_window_rate if @prev_conforming_messages.nil? || @prev_total_messages.nil?

  (@conforming_messages.to_f + @prev_conforming_messages.to_f) / (@total_messages + @prev_total_messages)
end