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/*
* =========================================================================================
* Copyright © 2013-2015 the kamon project <http://kamon.io/>
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the
* License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
* =========================================================================================
*/
package kamon.metric.instrument
import akka.actor.{Scheduler, Cancellable}
import org.HdrHistogram.WriterReaderPhaser
import scala.collection.concurrent.TrieMap
import scala.concurrent.ExecutionContext
import scala.concurrent.duration.FiniteDuration
trait RefreshScheduler {
def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable
}
/**
* Default implementation of RefreshScheduler that simply uses an [[akka.actor.Scheduler]] to schedule tasks to be run
* in the provided ExecutionContext.
*/
class DefaultRefreshScheduler(scheduler: Scheduler, dispatcher: ExecutionContext) extends RefreshScheduler {
def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable =
scheduler.schedule(interval, interval)(refresh.apply())(dispatcher)
}
object DefaultRefreshScheduler {
def apply(scheduler: Scheduler, dispatcher: ExecutionContext): RefreshScheduler =
new DefaultRefreshScheduler(scheduler, dispatcher)
def create(scheduler: Scheduler, dispatcher: ExecutionContext): RefreshScheduler =
apply(scheduler, dispatcher)
}
/**
* RefreshScheduler implementation that accumulates all the scheduled actions until it is pointed to another refresh
* scheduler. Once it is pointed, all subsequent calls to `schedule` will immediately be scheduled in the pointed
* scheduler.
*/
class LazyRefreshScheduler extends RefreshScheduler {
private val _schedulerPhaser = new WriterReaderPhaser
private val _backlog = new TrieMap[(FiniteDuration, () ⇒ Unit), RepointableCancellable]()
@volatile private var _target: Option[RefreshScheduler] = None
def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable = {
val criticalEnter = _schedulerPhaser.writerCriticalSectionEnter()
try {
_target.map { scheduler ⇒
scheduler.schedule(interval, refresh)
} getOrElse {
val entry = (interval, refresh)
val cancellable = new RepointableCancellable(entry)
_backlog.put(entry, cancellable)
cancellable
}
} finally {
_schedulerPhaser.writerCriticalSectionExit(criticalEnter)
}
}
def point(target: RefreshScheduler): Unit = try {
_schedulerPhaser.readerLock()
if (_target.isEmpty) {
_target = Some(target)
_schedulerPhaser.flipPhase(10000L)
_backlog.dropWhile {
case ((interval, refresh), repointableCancellable) ⇒
repointableCancellable.point(target.schedule(interval, refresh))
true
}
} else sys.error("A LazyRefreshScheduler cannot be pointed more than once.")
} finally { _schedulerPhaser.readerUnlock() }
class RepointableCancellable(entry: (FiniteDuration, () ⇒ Unit)) extends Cancellable {
private var _isCancelled = false
private var _cancellable: Option[Cancellable] = None
def isCancelled: Boolean = synchronized {
_cancellable.map(_.isCancelled).getOrElse(_isCancelled)
}
def cancel(): Boolean = synchronized {
_isCancelled = true
_cancellable.map(_.cancel()).getOrElse(_backlog.remove(entry).nonEmpty)
}
def point(cancellable: Cancellable): Unit = synchronized {
if (_cancellable.isEmpty) {
_cancellable = Some(cancellable)
if (_isCancelled)
cancellable.cancel()
} else sys.error("A RepointableCancellable cannot be pointed more than once.")
}
}
}
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