Class: Supervision::CircuitControl

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Defined in:
lib/supervision/circuit_control.rb

Overview

A class responsible for controling state of the circuit

Constant Summary collapse

MAX_THREAD_LIFETIME = 
5

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ CircuitControl

Create a circuit control

Parameters:

  • options (Hash) (defaults to: {}) 


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# File 'lib/supervision/circuit_control.rb', line 33

def initialize(options = {})
  @config            = Configuration.new(options)
  @failure_count     = Atomic.new(0)
  @last_failure_time = Atomic.new
  @lock              = Mutex.new
  @monitor           = CircuitMonitor.new
  fsm
end

Instance Attribute Details

#config ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

The circuit configuration



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# File 'lib/supervision/circuit_control.rb', line 14

def config
  @config
end

#monitor ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

The circuit performance monitor



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# File 'lib/supervision/circuit_control.rb', line 24

def monitor
  @monitor
end

#scheduler ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

The reset timeout scheduler



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# File 'lib/supervision/circuit_control.rb', line 19

def scheduler
  @scheduler
end

Instance Method Details

#fail_fast! ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Fail fast on any call

Raises:



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# File 'lib/supervision/circuit_control.rb', line 116

def fail_fast!
  monitor.measure(:open_circuit)
  raise CircuitBreakerOpenError
end

#failure_count ⇒ Integer

Total failure count for current circuit

Returns:

  • (Integer) 


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# File 'lib/supervision/circuit_control.rb', line 87

def failure_count
  @failure_count.value
end

#failure_count_exceeded? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:

  • (Boolean) 


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# File 'lib/supervision/circuit_control.rb', line 124

def failure_count_exceeded?
  failure_count > @config.max_failures
end

#fsm ⇒ FiniteMachine

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Creates internal finite state machine to transitions through three states :closed, :open and :half_open.

Returns:

  • (FiniteMachine) 


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# File 'lib/supervision/circuit_control.rb', line 49

def fsm
  context = self
  @fsm ||= FiniteMachine.define do
    initial :closed

    target context

    events do
      event :trip,         [:closed, :half_open] => :open
      event :attempt_reset, :open                => :half_open
      event :reset,         :half_open           => :closed
    end

    callbacks do
      on_enter :closed do |event|
        reset_failure
      end

      on_enter :open do |event|
        measure_timeout
        fail_fast!
      end

      on_enter :half_open do |event|
        monitor.measure(:half_open_circuit)
      end
    end
  end
end

#handle_failure(error = nil) ⇒ Object

Handler exception



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# File 'lib/supervision/circuit_control.rb', line 151

def handle_failure(error = nil)
  fail_fast! if fsm.open?
  record_failure
  monitor.record_failure
  trip if failure_count_exceeded? || fsm.half_open?
end

#last_failure_time ⇒ Time

Last time failure occured

Returns:

  • (Time) 


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# File 'lib/supervision/circuit_control.rb', line 96

def last_failure_time
  @last_failure_time.value
end

#max_thread_lifetime ⇒ Time

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Estimate maximum duration the scheduling thread should live

Returns:

  • (Time) 


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# File 'lib/supervision/circuit_control.rb', line 220

def max_thread_lifetime
  @config.reset_timeout + 100.milli
end

#measure_timeout ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Measure remaining timeout



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# File 'lib/supervision/circuit_control.rb', line 188

def measure_timeout
  @scheduler = Thread.new do
    Thread.current.abort_on_exception = true
    thread = Thread.current
    thread[:created_at] = Time.now
    @lock.synchronize do
      run_loop(thread)
    end
  end
end

#record_failure ⇒ Object

Record failure count



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# File 'lib/supervision/circuit_control.rb', line 170

def record_failure
  if fsm.closed? || fsm.half_open?
    @failure_count.update { |v| v + 1 }
    @last_failure_time.value = Time.now
  end
end

#record_success ⇒ Object

Record successful call



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# File 'lib/supervision/circuit_control.rb', line 161

def record_success
  reset if fsm.half_open?
  reset_failure
  monitor.record_success
end

#reset! ⇒ nil

Force closed state and reset failure statistics

Returns:

  • (nil) 


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# File 'lib/supervision/circuit_control.rb', line 105

def reset!
  fsm.reset!
  reset_failure
  throw(:terminate) if @scheduler && @scheduler.alive?
end

#reset_failure ⇒ Object

Resets failure count



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# File 'lib/supervision/circuit_control.rb', line 180

def reset_failure
  @failure_count.value = 0
  @last_failure_time.value = nil
end

#run_loop(thread) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Run scheduler loop



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# File 'lib/supervision/circuit_control.rb', line 202

def run_loop(thread)
  catch(:terminate) do
    loop do
      if tripped?
        attempt_reset && break
      elsif Time.now - thread[:created_at] > max_thread_lifetime
        thread.kill if thread.alive?
        break
      end
    end
  end
end

#timeout_exceeded? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Check if remaining duration until reset has been exceeded

Returns:

  • (Boolean) —

    whether or not the breaker will attempt a reset by transitioning to :half_open state



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# File 'lib/supervision/circuit_control.rb', line 142

def timeout_exceeded?
  return false unless last_failure_time
  timeout = Time.now - last_failure_time
  timeout > @config.reset_timeout
end

#tripped? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:

  • (Boolean) 


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# File 'lib/supervision/circuit_control.rb', line 131

def tripped?
  fsm.open? && timeout_exceeded?
end