Class: ResilientCall::Circuit

Inherits:
Object
  • Object
show all
Defined in:
lib/resilient_call/circuit.rb

Overview

Holds the state of a single named circuit and manages its transitions. Thread-safe: every public method runs under an internal Mutex.

closed --(threshold failures)--> open --(reset_timeout elapsed)--> half_open
  ^                                                                     |
  +------------------------- record_success! -------------------------+
half_open --(record_failure!)--> open  (restarts the timer)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, threshold: 5, reset_timeout: 60) ⇒ Circuit

Returns a new instance of Circuit.



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# File 'lib/resilient_call/circuit.rb', line 14

def initialize(name, threshold: 5, reset_timeout: 60)
  @name          = name
  @threshold     = threshold
  @reset_timeout = reset_timeout
  @state         = :closed
  @failure_count = 0
  @opened_at     = nil
  @last_failure  = nil
  @mutex         = Mutex.new
end

Instance Attribute Details

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/resilient_call/circuit.rb', line 12

def name
  @name
end

#reset_timeout ⇒ Object (readonly)

Returns the value of attribute reset_timeout.



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# File 'lib/resilient_call/circuit.rb', line 12

def reset_timeout
  @reset_timeout
end

#threshold ⇒ Object (readonly)

Returns the value of attribute threshold.



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# File 'lib/resilient_call/circuit.rb', line 12

def threshold
  @threshold
end

Instance Method Details

#allow_request? ⇒ Boolean

Whether a request may pass right now. An :open circuit whose reset_timeout has elapsed transitions to :half_open and lets a single probe through.

Returns:

  • (Boolean) 


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# File 'lib/resilient_call/circuit.rb', line 43

def allow_request?
  @mutex.synchronize do
    case @state
    when :closed
      true
    when :half_open
      true
    when :open
      if Time.now - @opened_at >= @reset_timeout
        @state = :half_open
        true
      else
        false
      end
    end
  end
end

#failure_count ⇒ Object 



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# File 'lib/resilient_call/circuit.rb', line 29

def failure_count
  @mutex.synchronize { @failure_count }
end

#last_failure ⇒ Object 



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# File 'lib/resilient_call/circuit.rb', line 33

def last_failure
  @mutex.synchronize { @last_failure }
end

#opened_at ⇒ Object 



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# File 'lib/resilient_call/circuit.rb', line 37

def opened_at
  @mutex.synchronize { @opened_at }
end

#record_failure!(error) ⇒ Object 



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# File 'lib/resilient_call/circuit.rb', line 73

def record_failure!(error)
  @mutex.synchronize do
    @failure_count += 1
    @last_failure   = error

    if @state == :half_open
      @state     = :open
      @opened_at = Time.now
    elsif @state == :closed && @failure_count >= @threshold
      @state     = :open
      @opened_at = Time.now
    end
  end
end

#record_success! ⇒ Object 



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# File 'lib/resilient_call/circuit.rb', line 61

def record_success!
  @mutex.synchronize do
    case @state
    when :half_open
      @state         = :closed
      @failure_count = 0
    when :closed
      @failure_count = 0
    end
  end
end

#reset! ⇒ Object 



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# File 'lib/resilient_call/circuit.rb', line 88

def reset!
  @mutex.synchronize do
    @state         = :closed
    @failure_count = 0
    @opened_at     = nil
    @last_failure  = nil
  end
end

#state ⇒ Object 



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# File 'lib/resilient_call/circuit.rb', line 25

def state
  @mutex.synchronize { @state }
end

#update_config(threshold: nil, reset_timeout: nil) ⇒ Object

Lets the entry point inject configured thresholds onto a circuit that was created lazily by the registry with default values.



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# File 'lib/resilient_call/circuit.rb', line 99

def update_config(threshold: nil, reset_timeout: nil)
  @mutex.synchronize do
    @threshold     = threshold     unless threshold.nil?
    @reset_timeout = reset_timeout unless reset_timeout.nil?
  end
end