akka.remote.DeadlineFailureDetector.scala Maven / Gradle / Ivy

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/**
 * Copyright (C) 2009-2014 Typesafe Inc. 
 */
package akka.remote

import scala.concurrent.duration.Duration
import scala.concurrent.duration.FiniteDuration
import com.typesafe.config.Config
import akka.event.EventStream
import akka.remote.FailureDetector.Clock
import akka.util.Helpers.ConfigOps

/**
 * Implementation of failure detector using an absolute timeout of missing heartbeats
 * to trigger unavailability.
 *
 * @param acceptableHeartbeatPause Duration corresponding to number of potentially lost/delayed
 *   heartbeats that will be accepted before considering it to be an anomaly.
 *
 * @param clock The clock, returning current time in milliseconds, but can be faked for testing
 *   purposes. It is only used for measuring intervals (duration).
 */
class DeadlineFailureDetector(
  val acceptableHeartbeatPause: FiniteDuration)(
    implicit clock: Clock) extends FailureDetector {

  /**
   * Constructor that reads parameters from config.
   * Expecting config properties named `acceptable-heartbeat-pause`.
   */
  def this(config: Config, ev: EventStream) =
    this(acceptableHeartbeatPause = config.getMillisDuration("acceptable-heartbeat-pause"))

  require(acceptableHeartbeatPause >= Duration.Zero, "failure-detector.acceptable-heartbeat-pause must be >= 0")

  private val acceptableHeartbeatPauseMillis = acceptableHeartbeatPause.toMillis
  @volatile private var heartbeatTimestamp = 0L //not used until active (first heartbeat)
  @volatile private var active = false

  override def isAvailable: Boolean = isAvailable(clock())

  private def isAvailable(timestamp: Long): Boolean =
    if (active) (heartbeatTimestamp + acceptableHeartbeatPauseMillis) > timestamp
    else true // treat unmanaged connections, e.g. with zero heartbeats, as healthy connections

  override def isMonitoring: Boolean = active

  final override def heartbeat(): Unit = {
    heartbeatTimestamp = clock()
    active = true
  }

}