Class: Seekmodo::Sdk::CircuitBreaker

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

Constant Summary collapse

STATE_CLOSED = 
"closed"
STATE_OPEN = 
"open"
STATE_HALFOPEN = 
"half_open"

Instance Method Summary collapse

Constructor Details

#initialize(store, key: "numinix.seekmodo.circuit", failure_threshold: 5, failure_window_seconds: 60, open_cooldown_seconds: 30, clock: nil) ⇒ CircuitBreaker

Returns a new instance of CircuitBreaker.



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# File 'lib/seekmodo/sdk/circuit_breaker.rb', line 12

def initialize(
  store,
  key: "numinix.seekmodo.circuit",
  failure_threshold: 5,
  failure_window_seconds: 60,
  open_cooldown_seconds: 30,
  clock: nil
)
  @store = store
  @key = key
  @failure_threshold = failure_threshold
  @failure_window_seconds = failure_window_seconds
  @open_cooldown_seconds = open_cooldown_seconds
  @clock = clock || -> { Time.now.to_i }
end

Instance Method Details

#allow_request? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/seekmodo/sdk/circuit_breaker.rb', line 28

def allow_request?
  state = load_state
  now = @clock.call

  if state["state"] == STATE_OPEN
    if now - state["opened_at"].to_i >= @open_cooldown_seconds
      state["state"] = STATE_HALFOPEN
      state["probe_in_flight"] = true
      save_state(state)
      return true
    end
    return false
  end

  if state["state"] == STATE_HALFOPEN
    return false if state["probe_in_flight"]

    state["probe_in_flight"] = true
    save_state(state)
    return true
  end

  true
end

#record_failure ⇒ Object 



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# File 'lib/seekmodo/sdk/circuit_breaker.rb', line 71

def record_failure
  state = load_state
  now = @clock.call

  if state["state"] == STATE_HALFOPEN
    save_state(
      "state" => STATE_OPEN,
      "failures" => [],
      "opened_at" => now,
      "probe_in_flight" => false
    )
    return
  end

  failures = state["failures"] + [now]
  cutoff = now - @failure_window_seconds
  failures = failures.select { |ts| ts >= cutoff }

  if failures.length >= @failure_threshold
    save_state(
      "state" => STATE_OPEN,
      "failures" => [],
      "opened_at" => now,
      "probe_in_flight" => false
    )
    return
  end

  state["failures"] = failures
  save_state(state)
end

#record_success ⇒ Object 



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# File 'lib/seekmodo/sdk/circuit_breaker.rb', line 53

def record_success
  state = load_state
  if [STATE_HALFOPEN, STATE_OPEN].include?(state["state"])
    save_state(
      "state" => STATE_CLOSED,
      "failures" => [],
      "opened_at" => 0,
      "probe_in_flight" => false
    )
    return
  end

  if state["failures"].any?
    state["failures"] = []
    save_state(state)
  end
end

#snapshot ⇒ Object 



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# File 'lib/seekmodo/sdk/circuit_breaker.rb', line 107

def snapshot
  load_state
end

#state ⇒ Object 



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# File 'lib/seekmodo/sdk/circuit_breaker.rb', line 103

def state
  load_state["state"]
end