kafka.utils.KafkaScheduler.scala Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 kafka.utils
import java.util.concurrent._
import atomic._
import org.apache.kafka.common.utils.Utils
/**
* A scheduler for running jobs
*
* This interface controls a job scheduler that allows scheduling either repeating background jobs
* that execute periodically or delayed one-time actions that are scheduled in the future.
*/
trait Scheduler {
/**
* Initialize this scheduler so it is ready to accept scheduling of tasks
*/
def startup()
/**
* Shutdown this scheduler. When this method is complete no more executions of background tasks will occur.
* This includes tasks scheduled with a delayed execution.
*/
def shutdown()
/**
* Check if the scheduler has been started
*/
def isStarted: Boolean
/**
* Schedule a task
* @param name The name of this task
* @param delay The amount of time to wait before the first execution
* @param period The period with which to execute the task. If < 0 the task will execute only once.
* @param unit The unit for the preceding times.
*/
def schedule(name: String, fun: ()=>Unit, delay: Long = 0, period: Long = -1, unit: TimeUnit = TimeUnit.MILLISECONDS)
}
/**
* A scheduler based on java.util.concurrent.ScheduledThreadPoolExecutor
*
* It has a pool of kafka-scheduler- threads that do the actual work.
*
* @param threads The number of threads in the thread pool
* @param threadNamePrefix The name to use for scheduler threads. This prefix will have a number appended to it.
* @param daemon If true the scheduler threads will be "daemon" threads and will not block jvm shutdown.
*/
@threadsafe
class KafkaScheduler(val threads: Int,
val threadNamePrefix: String = "kafka-scheduler-",
daemon: Boolean = true) extends Scheduler with Logging {
private var executor: ScheduledThreadPoolExecutor = null
private val schedulerThreadId = new AtomicInteger(0)
override def startup() {
debug("Initializing task scheduler.")
this synchronized {
if(isStarted)
throw new IllegalStateException("This scheduler has already been started!")
executor = new ScheduledThreadPoolExecutor(threads)
executor.setContinueExistingPeriodicTasksAfterShutdownPolicy(false)
executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false)
executor.setThreadFactory(new ThreadFactory() {
def newThread(runnable: Runnable): Thread =
Utils.newThread(threadNamePrefix + schedulerThreadId.getAndIncrement(), runnable, daemon)
})
}
}
override def shutdown() {
debug("Shutting down task scheduler.")
// We use the local variable to avoid NullPointerException if another thread shuts down scheduler at same time.
val cachedExecutor = this.executor
if (cachedExecutor != null) {
this synchronized {
cachedExecutor.shutdown()
this.executor = null
}
cachedExecutor.awaitTermination(1, TimeUnit.DAYS)
}
}
def schedule(name: String, fun: ()=>Unit, delay: Long, period: Long, unit: TimeUnit) {
debug("Scheduling task %s with initial delay %d ms and period %d ms."
.format(name, TimeUnit.MILLISECONDS.convert(delay, unit), TimeUnit.MILLISECONDS.convert(period, unit)))
this synchronized {
ensureRunning
val runnable = CoreUtils.runnable {
try {
trace("Beginning execution of scheduled task '%s'.".format(name))
fun()
} catch {
case t: Throwable => error("Uncaught exception in scheduled task '" + name +"'", t)
} finally {
trace("Completed execution of scheduled task '%s'.".format(name))
}
}
if(period >= 0)
executor.scheduleAtFixedRate(runnable, delay, period, unit)
else
executor.schedule(runnable, delay, unit)
}
}
def isStarted: Boolean = {
this synchronized {
executor != null
}
}
private def ensureRunning = {
if(!isStarted)
throw new IllegalStateException("Kafka scheduler is not running.")
}
}