com.thebuzzmedia.exiftool.core.schedulers.DefaultScheduler Maven / Gradle / Ivy
/**
* Copyright 2011 The Buzz Media, LLC
* Copyright 2015 Mickael Jeanroy
*
* 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 com.thebuzzmedia.exiftool.core.schedulers;
import com.thebuzzmedia.exiftool.Scheduler;
import com.thebuzzmedia.exiftool.logs.Logger;
import com.thebuzzmedia.exiftool.logs.LoggerFactory;
import java.util.concurrent.RunnableFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import static com.thebuzzmedia.exiftool.commons.lang.PreConditions.notNull;
import static com.thebuzzmedia.exiftool.core.schedulers.SchedulerDuration.duration;
import static com.thebuzzmedia.exiftool.core.schedulers.SchedulerDuration.millis;
import static com.thebuzzmedia.exiftool.core.schedulers.SchedulerDuration.seconds;
/**
* Default implementation for {@code exiftool} {@link com.thebuzzmedia.exiftool.Scheduler}.
*
*
*
* This scheduler will execute a task in a specified amount of time:
*
*
* - Time must be specified during construction.
* - Time unit (milliseconds, seconds, hours, etc.) may be defined during construction.
*
*
* Note: This scheduler will stop pending task when instance is
* garbage collected. This is just a small security but we cannot guarantee when
* instance will be garbage collected. For this reason, it should be up to the caller
* to stop this scheduler when it is not needed anymore.
*/
public class DefaultScheduler implements Scheduler {
/**
* Class Logger.
*/
private static final Logger log = LoggerFactory.getLogger(DefaultScheduler.class);
/**
* Delay before task execution.
*/
private final SchedulerDuration executionDelay;
/**
* Delay to wait for scheduler termination.
*/
private final SchedulerDuration terminationDelay;
/**
* Executor used to defer task execution.
* This withExecutor will produce instance of {@link RunnableFuture} tasks.
*/
private final ScheduledThreadPoolExecutor executor;
/**
* Create new scheduler.
* Default time unit is {@link TimeUnit#MILLISECONDS}.
* A default withExecutor will be created.
*
* @param delay Delay.
* @throws IllegalArgumentException If {@code delay} is less than or equal to zero.
* @deprecated Use {@link #DefaultScheduler(SchedulerDuration)} instead.
*/
@Deprecated
public DefaultScheduler(long delay) {
this(millis(delay));
}
/**
* Create new scheduler.
* A default withExecutor will be created.
*
* @param delay Delay.
* @param timeUnit Time Unit.
* @throws NullPointerException If {@code timeUnit} is {@code null}.
* @throws IllegalArgumentException If {@code delay} is less than or equal to zero.
* @deprecated Use {@link #DefaultScheduler(SchedulerDuration)} instead.
*/
@Deprecated
public DefaultScheduler(long delay, TimeUnit timeUnit) {
this(duration(delay, timeUnit));
}
/**
* Create new scheduler.
* Default time unit is {@link TimeUnit#MILLISECONDS}.
* A default withExecutor will be created.
*
* @param executionDelay The delay between execution.
* @throws IllegalArgumentException If {@code delay} is less than or equal to zero.
*/
public DefaultScheduler(SchedulerDuration executionDelay) {
this(executionDelay, seconds(5));
}
/**
* Create new scheduler.
* A default withExecutor will be created.
*
* @param executionDelay The delay between scheduler execution.
* @param terminationDelay The delay to use to wait for termination when scheduler is shutting down.
* @throws NullPointerException If {@code timeUnit} is {@code null}.
* @throws IllegalArgumentException If {@code delay} is less than or equal to zero.
*/
public DefaultScheduler(SchedulerDuration executionDelay, SchedulerDuration terminationDelay) {
this.executionDelay = notNull(executionDelay, "Execution delay must not be null");
this.terminationDelay = notNull(terminationDelay, "Termination delay must not be null");
// Create executor
this.executor = new ScheduledThreadPoolExecutor(1);
this.executor.setRemoveOnCancelPolicy(true);
}
@Override
public synchronized void start(Runnable runnable) {
executor.schedule(runnable, executionDelay.getDelay(), executionDelay.getTimeUnit());
}
@Override
public synchronized void stop() {
for (Runnable runnable : executor.getQueue()) {
((RunnableFuture>) runnable).cancel(false);
}
executor.purge();
}
@Override
public synchronized void shutdown() {
stop();
processShutdown();
}
private void processShutdown() {
log.debug("Shutdown scheduler");
// Disable new tasks from being submitted
executor.shutdown();
try {
log.debug("Wait for scheduler termination");
// Wait a while for existing tasks to terminate
if (!executor.awaitTermination(terminationDelay.getDelay(), terminationDelay.getTimeUnit())) {
// Cancel currently executing tasks
log.debug("Termination seems to failed, shutdown now");
executor.shutdownNow();
// Wait a while for tasks to respond to being cancelled
if (!executor.awaitTermination(terminationDelay.getDelay(), terminationDelay.getTimeUnit())) {
log.error("Scheduler did not seem to terminate");
}
}
}
catch (InterruptedException ie) {
// (Re-)Cancel if current thread also interrupted
executor.shutdownNow();
// Preserve interrupt status
Thread.currentThread().interrupt();
}
}
// Implement finalizer.
// This is just a small security to stop scheduled task if
// instance is garbage collected.
@Override
protected void finalize() throws Throwable {
super.finalize();
shutdown();
}
}
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