Class: Rapidity::Limiter

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

Constant Summary collapse

LUA_SCRIPT_CODE = 
File.read(File.join(__dir__, 'limiter.lua'))

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pool, name:, interval: 10, threshold: 10, namespace: 'rapidity') ⇒ Limiter

Convert message to given class



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# File 'lib/rapidity/limiter.rb', line 17

def initialize(pool, name:, interval: 10, threshold: 10, namespace: 'rapidity')
  @pool = pool
  @interval = interval
  @threshold = threshold
  @name = name

  @namespace = namespace
end

Instance Attribute Details

#interval ⇒ Object (readonly)

Returns the value of attribute interval.



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# File 'lib/rapidity/limiter.rb', line 7

def interval
  @interval
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/rapidity/limiter.rb', line 7

def name
  @name
end

#namespace ⇒ Object (readonly)

Returns the value of attribute namespace.



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# File 'lib/rapidity/limiter.rb', line 7

def namespace
  @namespace
end

#pool ⇒ Object (readonly)

Returns the value of attribute pool.



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# File 'lib/rapidity/limiter.rb', line 7

def pool
  @pool
end

#threshold ⇒ Object (readonly)

Returns the value of attribute threshold.



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# File 'lib/rapidity/limiter.rb', line 7

def threshold
  @threshold
end

Instance Method Details

#ensure_script_loaded ⇒ Object 



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# File 'lib/rapidity/limiter.rb', line 92

def ensure_script_loaded
  @script = @pool.with do |conn|
    conn.script(:load, LUA_SCRIPT_CODE)
  end
end

#force_ttl(ttl) ⇒ Object 



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# File 'lib/rapidity/limiter.rb', line 86

def force_ttl(ttl)
  @pool.with do |conn|
    conn.expire(key('remains'), ttl)
  end
end

#key(path) ⇒ Object 



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# File 'lib/rapidity/limiter.rb', line 26

def key(path)
  "#{namespace}:#{name}_#{path}"
end

#obtain(count = 5, with_time: false) ⇒ Object

Obtain values from counter

Returns:

  • count succesfuly obtained send slots



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# File 'lib/rapidity/limiter.rb', line 46

def obtain(count = 5, with_time: false)
  count = count.abs

  result = begin
    @pool.with do |conn|
      conn.evalsha(@script, keys: [key('remains')], argv: [threshold, interval, count])
    end
  rescue Redis::CommandError => e
    if e.message.include?('NOSCRIPT')
      # The Redis server has never seen this script before. Needs to run only once in the entire lifetime
      # of the Redis server, until the script changes - in which case it will be loaded under a different SHA
      ensure_script_loaded
      retry
    else
      raise e
    end
  end

  taken = result[0].to_i
  time = Time.at(*result[1].map(&:to_i), :millisecond)

  if taken == 0
    ttl = @pool.with do |conn|
      conn.ttl(key('remains'))
    end

    # UNKNOWN BUG? reset if no ttl present. Many years ago once upon time we meet our key without TTL
    if ttl == -1
      STDERR.puts "ERROR[#{Time.now}]: TTL for key #{key('remains').inspect} disappeared!"
      @pool.with {|c| c.expire(key('remains'), interval) }
    end
  end

  if with_time
    [taken, time]
  else
    taken
  end
end

#remains ⇒ Object

Get current counter

Returns:

  • remaining counter value



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# File 'lib/rapidity/limiter.rb', line 32

def remains
  results = @pool.with do |conn|
    conn.multi do |pipeline|
      pipeline.set(key('remains'), threshold, ex: interval, nx: true)
      pipeline.get(key('remains'))
    end
  end
  results[1].to_i #=> pipeline.get(key('remains'))
end