Class: HTTPigeon::CircuitBreaker::Fuse

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

Constant Summary collapse

STATE_OPEN = 
'open'.freeze
STATE_HALF_OPEN = 
'half_open'.freeze
STATE_CLOSED = 
'closed'.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config) ⇒ Fuse

Returns a new instance of Fuse.



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 19

def initialize(config)
  @config = config
  @service_id = config.service_id.to_s
  @store = CircuitBreaker::MemoryStore.new(config.sample_window)
  @open_storage_key = "circuit:#{service_id}:#{STATE_OPEN}"
  @half_open_storage_key = "circuit:#{service_id}:#{STATE_HALF_OPEN}"
  @state_change_syncer = Mutex.new
end

Instance Attribute Details

#config ⇒ Object (readonly)

Returns the value of attribute config.



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 17

def config
  @config
end

#service_id ⇒ Object (readonly)

Returns the value of attribute service_id.



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 17

def service_id
  @service_id
end

#store ⇒ Object (readonly)

Returns the value of attribute store.



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 17

def store
  @store
end

Class Method Details

.from_options(options) ⇒ Object 



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 13

def self.from_options(options)
  new(FuseConfig.new(options))
end

Instance Method Details

#execute(request_id: nil) ⇒ Object 



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 28

def execute(request_id: nil)
  @request_id = request_id

  if open?
    record_tripped!

    config.open_circuit_handler.call(config.null_response, config.circuit_open_error)
  else
    begin
      response = yield
      server_maintenance_timeout = response.headers[config.maintenance_mode_header].to_i

      if server_maintenance_timeout.positive?
        record_failure!
        open!(
          {
            expires_in: server_maintenance_timeout,
            # for logging purposes. can't log expires_in because it might be overridden if greater than max
            server_maintenance_timeout: server_maintenance_timeout
          }
        )

        return config.open_circuit_handler.call(response, config.circuit_open_error)
      end

      record_success!
      response
    rescue Faraday::Error => e
      record_failure! if e.response_status >= 500 || config.error_codes_watchlist.include?(e.response_status)

      raise e
    end
  end
end

#failure_count ⇒ Object 



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 71

def failure_count
  store.get(stat_storage_key(:failure)).to_i
end

#failure_rate ⇒ Object 



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 83

def failure_rate
  total_stats = success_count + failure_count + tripped_count

  return 0.0 unless total_stats.positive?

  (total_stats - success_count).to_f / total_stats
end

#half_open? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 67

def half_open?
  store.key?(half_open_storage_key)
end

#open? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 63

def open?
  store.key?(open_storage_key)
end

#reset! ⇒ Object 



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 91

def reset!
  state_change_syncer.synchronize { store.reset! }
end

#success_count ⇒ Object 



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 75

def success_count
  store.get(stat_storage_key(:success)).to_i
end

#tripped_count ⇒ Object 



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# File 'lib/httpigeon/circuit_breaker/fuse.rb', line 79

def tripped_count
  store.get(stat_storage_key(:tripped)).to_i
end