Class: Philiprehberger::RateLimiter::SlidingWindow

Inherits:
Object
  • Object
show all
Includes:
StatsTracking
Defined in:
lib/philiprehberger/rate_limiter/sliding_window.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from StatsTracking

#allow!, #block, #keys, #on_reject, #stats, #throttle

Constructor Details

#initialize(limit:, window:, max_keys: nil) ⇒ SlidingWindow

Returns a new instance of SlidingWindow.

Parameters:

  • limit (Integer) —

    max requests allowed per window

  • window (Numeric) —

    window duration in seconds

  • max_keys (Integer, nil) (defaults to: nil) —

    cap on tracked keys; least-recently-touched key is evicted (LRU) once the cap is exceeded. nil means unbounded.



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 16

def initialize(limit:, window:, max_keys: nil)
  @limit = limit
  @window = window
  @max_keys = max_keys
  @store = {}
  @mutex = Mutex.new
  init_stats
end

Instance Attribute Details

#limit ⇒ Object (readonly)

Returns the value of attribute limit.



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 10

def limit
  @limit
end

#window ⇒ Object (readonly)

Returns the value of attribute window.



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 10

def window
  @window
end

Instance Method Details

#allow?(key, weight: 1) ⇒ Boolean

Check if a request is allowed and consume slot(s) in the window.

Parameters:

  • key (Symbol, String) —

    the rate limit key

  • weight (Integer) (defaults to: 1) —

    number of slots to consume (default 1)

Returns:

  • (Boolean) —

    true if the request was allowed, false if rejected



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 30

def allow?(key, weight: 1)
  @mutex.synchronize { try_acquire(key, weight) }
end

#allow_batch(keys) ⇒ Hash{Object => Boolean}

Check many keys in a single mutex acquisition.

Parameters:

  • keys (Array<Symbol, String>) —

    the keys to check and consume

Returns:

  • (Hash{Object => Boolean}) —

    mapping of each key to the allow result



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 38

def allow_batch(keys)
  @mutex.synchronize do
    keys.to_h { |key| [key, try_acquire(key, 1)] }
  end
end

#clear ⇒ void

This method returns an undefined value.

Clear state for all keys (resets quotas and stats for every tracked key)



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 82

def clear
  @mutex.synchronize do
    @store.clear
    @stats_store.clear
  end
  nil
end

#drain(key = :default) ⇒ Integer

Forcefully consume all remaining capacity for a key.

Parameters:

  • key (Symbol, String) (defaults to: :default) —

    the rate limit key

Returns:

  • (Integer) —

    the number of slots drained



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 143

def drain(key = :default)
  @mutex.synchronize { drain_entries(key) }
end

#info(key) ⇒ Hash

Build a usage info hash for a key.

Parameters:

  • key (Symbol, String) —

    the rate limit key

Returns:

  • (Hash) —

    keys :remaining, :reset_at, :limit, :window, :used



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 94

def info(key)
  @mutex.synchronize { build_info(key) }
end

#info_batch(keys) ⇒ Hash{Object => Hash}

Build info hashes for many keys in a single mutex acquisition.

Mirrors #allow_batch for inspection rather than acquisition.

Parameters:

  • keys (Array<Symbol, String>) —

    the keys to inspect

Returns:

  • (Hash{Object => Hash}) —

    mapping of each key to its info hash



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 104

def info_batch(keys)
  @mutex.synchronize do
    keys.to_h { |key| [key, build_info(key)] }
  end
end

#peek(key) ⇒ Boolean

Check if a request would be allowed without consuming a slot.

Parameters:

  • key (Symbol, String) —

    the rate limit key

Returns:

  • (Boolean) —

    true if capacity is available, false otherwise



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 48

def peek(key)
  @mutex.synchronize { count_remaining(key).positive? }
end

#prune ⇒ Integer

Drop keys whose window is empty (all entries have expired), reclaiming memory for idle keys. Also clears their stats.

Returns:

  • (Integer) —

    the number of keys pruned



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 123

def prune
  @mutex.synchronize do
    pruned = 0
    tracked = @store.keys
    tracked.each do |key|
      cleanup(key)
      next unless @store[key].empty?

      @store.delete(key)
      @stats_store.delete(key)
      pruned += 1
    end
    pruned
  end
end

#refund(key, amount: 1) ⇒ nil

Return previously consumed slot(s) to a key (e.g. on downstream failure).

Parameters:

  • key (Symbol, String) —

    the rate limit key

  • amount (Integer) (defaults to: 1) —

    number of slots to refund (default 1)

Returns:

  • (nil) 


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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 115

def refund(key, amount: 1)
  @mutex.synchronize { refund_entries(key, amount) }
end

#remaining(key) ⇒ Integer

Return the number of remaining slots in the current window.

Parameters:

  • key (Symbol, String) —

    the rate limit key

Returns:

  • (Integer) —

    count of remaining capacity (0 if at or over limit)



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 56

def remaining(key)
  @mutex.synchronize { count_remaining(key) }
end

#reset(key) ⇒ void

This method returns an undefined value.

Clear the window for a key, discarding all tracked entries.

Parameters:

  • key (Symbol, String) —

    the rate limit key



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 75

def reset(key)
  @mutex.synchronize { @store.delete(key.to_s) }
end

#retry_after(key = :default) ⇒ Float

Seconds until the next request would be allowed, suitable for the HTTP Retry-After header. Returns 0.0 when a request is allowed right now.

Parameters:

  • key (Symbol, String) (defaults to: :default) —

    the rate limit key

Returns:

  • (Float) —

    seconds until next allowed request (0.0 if allowed now)



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 170

def retry_after(key = :default)
  @mutex.synchronize do
    cleanup(key)
    entries = fetch_entries(key)
    return 0.0 if entries.length < @limit

    oldest = entries.min
    return 0.0 if oldest.nil?

    wait = (oldest + @window) - now
    [wait, 0.0].max
  end
end

#used(key) ⇒ Integer

Number of currently consumed slots for a key (after expiring old entries).

Parameters:

  • key (Symbol, String) —

    the rate limit key

Returns:

  • (Integer) —

    count of active entries in the window



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 64

def used(key)
  @mutex.synchronize do
    cleanup(key)
    fetch_entries(key).length
  end
end

#wait_time(key = :default) ⇒ Float

Seconds until the next request would be allowed

Parameters:

  • key (Symbol, String) (defaults to: :default) —

    the rate limit key

Returns:

  • (Float) —

    seconds to wait (0 if allowed now)



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 151

def wait_time(key = :default)
  @mutex.synchronize do
    cleanup(key)
    entries = fetch_entries(key)
    return 0.0 if entries.length < @limit

    oldest = entries.min
    return 0.0 if oldest.nil?

    wait = oldest + @window - now
    [wait, 0.0].max
  end
end

#window_reset_at(key = :default) ⇒ Time?

Time when the current window expires

Parameters:

  • key (Symbol, String) (defaults to: :default) —

    the rate limit key

Returns:

  • (Time, nil) —

    absolute time when window resets, nil if no requests



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# File 'lib/philiprehberger/rate_limiter/sliding_window.rb', line 188

def window_reset_at(key = :default)
  @mutex.synchronize do
    entries = fetch_entries(key)
    return nil if entries.empty?

    cleanup(key)
    entries = fetch_entries(key)
    return nil if entries.empty?

    oldest = entries.min
    elapsed = now - oldest
    Time.now + (@window - elapsed)
  end
end