org.bitcoinj.manager.ManagerFiles Maven / Gradle / Ivy
/*
* Copyright 2013 Google Inc.
* Copyright 2014 Andreas Schildbach
* Copyright 2022 Dash Core Group
*
* 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 org.bitcoinj.manager;
import com.google.common.base.Stopwatch;
import org.bitcoinj.core.AbstractManager;
import org.bitcoinj.utils.ContextPropagatingThreadFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.annotation.Nonnull;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import static com.google.common.base.Preconditions.checkNotNull;
/**
* A class that handles atomic and optionally delayed writing of a manager file to disk. In future: backups too.
* It can be useful to delay writing of a manager file to disk on slow devices where disk and serialization overhead
* can come to dominate the chain processing speed, i.e. on Android phones. By coalescing writes and doing serialization
* and disk IO on a background thread performance can be improved.
*/
public class ManagerFiles {
private static final Logger log = LoggerFactory.getLogger(ManagerFiles.class);
private final AbstractManager manager;
private final ScheduledThreadPoolExecutor executor;
private final File file;
private final AtomicBoolean savePending;
private final long delay;
private final TimeUnit delayTimeUnit;
private final Callable saver;
private volatile Listener vListener;
/**
* Implementors can do pre/post treatment of the manager file. Useful for adjusting permissions and other things.
*/
public interface Listener {
/**
* Called on the auto-save thread when a new temporary file is created but before the manager data is saved
* to it. If you want to do something here like adjust permissions, go ahead and do so.
*/
void onBeforeAutoSave(File tempFile);
/**
* Called on the auto-save thread after the newly created temporary file has been filled with data and renamed.
*/
void onAfterAutoSave(File newlySavedFile);
}
/**
* Initialize atomic and optionally delayed writing of the manager file to disk. Note the initial manager state isn't
* saved automatically. The {@link AbstractManager} calls {@link #saveNow()} or {@link #saveLater()} as manager state changes,
* depending on the urgency of the changes.
*/
public ManagerFiles(final AbstractManager manager, File file, long delay, TimeUnit delayTimeUnit) {
// An executor that starts up threads when needed and shuts them down later.
this.executor = new ScheduledThreadPoolExecutor(1, new ContextPropagatingThreadFactory("AbstractManager autosave thread", Thread.MIN_PRIORITY));
this.executor.setKeepAliveTime(5, TimeUnit.SECONDS);
this.executor.allowCoreThreadTimeOut(true);
this.executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
this.manager = checkNotNull(manager);
// File must only be accessed from the auto-save executor from now on, to avoid simultaneous access.
this.file = checkNotNull(file);
this.savePending = new AtomicBoolean();
this.delay = delay;
this.delayTimeUnit = checkNotNull(delayTimeUnit);
this.saver = new Callable() {
@Override public Void call() throws Exception {
// Runs in an auto save thread.
if (!savePending.getAndSet(false)) {
// Some other scheduled request already beat us to it.
return null;
}
log.info("Background saving manager");
saveNowInternal();
return null;
}
};
}
/** Get the {@link AbstractManager} this {@link ManagerFiles} is managing. */
public AbstractManager getManager() {
return manager;
}
/**
* The given listener will be called on the autosave thread before and after the manager is saved to disk.
*/
public void setListener(@Nonnull Listener listener) {
this.vListener = checkNotNull(listener);
}
/** Actually write the manager file to disk, using an atomic rename when possible. Runs on the current thread. */
public void saveNow() throws IOException {
// Can be called by any thread. However the manager is locked whilst saving, so we can have two saves in flight
// but they will serialize (using different temp files).
if (executor.isShutdown())
return;
log.info("Saving manager file: {}", file.getAbsolutePath());
saveNowInternal();
}
private void saveNowInternal() throws IOException {
final Stopwatch watch = Stopwatch.createStarted();
File directory = file.getAbsoluteFile().getParentFile();
File temp = File.createTempFile("manager", null, directory);
final Listener listener = vListener;
if (listener != null)
listener.onBeforeAutoSave(temp);
manager.saveToFile(temp, file);
if (listener != null)
listener.onAfterAutoSave(file);
watch.stop();
log.info("Save completed in {} to {}", watch, file.getAbsolutePath());
}
/** Queues up a save in the background. Useful for not very important manager changes. */
public void saveLater() {
if (executor.isShutdown() || savePending.getAndSet(true))
return; // Already pending.
executor.schedule(saver, delay, delayTimeUnit);
}
/** Shut down auto-saving. */
public void shutdownAndWait() {
executor.shutdown();
try {
executor.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS); // forever
} catch (InterruptedException x) {
throw new RuntimeException(x);
}
}
}