Class: Pgbus::RateCounter

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

Overview

Thread-safe rate counter inspired by LavinMQ’s rate_stats macro. Tracks absolute counts via AtomicFixnum and computes rates as deltas between periodic snapshots.

Usage:

counter = RateCounter.new(:enqueued, :dequeued, :failed)
counter.increment(:enqueued)
counter.snapshot!          # call periodically (e.g. every 5s)
counter.rate(:enqueued)    # => msgs/s since last snapshot
counter.rates              # => { enqueued: 12.4, dequeued: 10.1, failed: 0.2 }

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*names) ⇒ RateCounter

Returns a new instance of RateCounter.



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# File 'lib/pgbus/rate_counter.rb', line 19

def initialize(*names)
  @names = names.map(&:to_sym)
  @counters = {}
  @last_values = {}
  @rates = {}
  @last_snapshot_at = monotonic_now

  @names.each do |name|
    @counters[name] = Concurrent::AtomicFixnum.new(0)
    @last_values[name] = 0
    @rates[name] = 0.0
  end
end

Instance Attribute Details

#names ⇒ Object (readonly)

Returns the value of attribute names.



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# File 'lib/pgbus/rate_counter.rb', line 17

def names
  @names
end

Instance Method Details

#count(name) ⇒ Object 



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# File 'lib/pgbus/rate_counter.rb', line 37

def count(name)
  @counters.fetch(name).value
end

#counts ⇒ Object 



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# File 'lib/pgbus/rate_counter.rb', line 49

def counts
  @names.to_h { |name| [name, @counters[name].value] }
end

#increment(name, delta = 1) ⇒ Object 



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# File 'lib/pgbus/rate_counter.rb', line 33

def increment(name, delta = 1)
  @counters.fetch(name).increment(delta)
end

#rate(name) ⇒ Object 



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# File 'lib/pgbus/rate_counter.rb', line 41

def rate(name)
  @rates.fetch(name)
end

#rates ⇒ Object 



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# File 'lib/pgbus/rate_counter.rb', line 45

def rates
  @names.to_h { |name| [name, @rates[name]] }
end

#snapshot! ⇒ Object 



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# File 'lib/pgbus/rate_counter.rb', line 53

def snapshot!
  now = monotonic_now
  elapsed = now - @last_snapshot_at
  return if elapsed <= 0

  @names.each do |name|
    current = @counters[name].value
    delta = current - @last_values[name]
    @rates[name] = (delta / elapsed).round(1)
    @last_values[name] = current
  end

  @last_snapshot_at = now
end

#to_h ⇒ Object 



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# File 'lib/pgbus/rate_counter.rb', line 68

def to_h
  {
    counts: counts,
    rates: rates
  }
end