Class: ActsAsTbackend::CircuitBreaker

Inherits:
Object
  • Object
show all
Defined in:
lib/acts_as_tbackend/circuit_breaker.rb

Overview

A small thread-safe circuit breaker per (host, port). After threshold consecutive failures it opens for cooldown seconds, then allows a single half-open probe. Keeps a down daemon from stalling every request thread (fail-fast) while a shadow write stays non-fatal.

Instance Method Summary collapse

Constructor Details

#initialize(threshold:, cooldown:) ⇒ CircuitBreaker

Returns a new instance of CircuitBreaker.



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# File 'lib/acts_as_tbackend/circuit_breaker.rb', line 9

def initialize(threshold:, cooldown:)
  @threshold = threshold
  @cooldown = cooldown
  @failures = 0
  @opened_at = nil
  @mutex = Mutex.new
end

Instance Method Details

#allow_request? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/acts_as_tbackend/circuit_breaker.rb', line 17

def allow_request?
  @mutex.synchronize do
    return true if @opened_at.nil?
    return true if (monotonic - @opened_at) >= @cooldown # half-open probe

    false
  end
end

#open? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/acts_as_tbackend/circuit_breaker.rb', line 40

def open?
  @mutex.synchronize { !@opened_at.nil? && (monotonic - @opened_at) < @cooldown }
end

#record_failure ⇒ Object 



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# File 'lib/acts_as_tbackend/circuit_breaker.rb', line 33

def record_failure
  @mutex.synchronize do
    @failures += 1
    @opened_at = monotonic if @failures >= @threshold
  end
end

#record_success ⇒ Object 



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# File 'lib/acts_as_tbackend/circuit_breaker.rb', line 26

def record_success
  @mutex.synchronize do
    @failures = 0
    @opened_at = nil
  end
end