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/*
* Copyright 2013 Google Inc.
* Copyright 2014 Andreas Schildbach
*
* 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.wallet;
import org.bitcoinj.core.*;
import org.bitcoinj.utils.*;
import org.slf4j.*;
import com.google.common.base.Stopwatch;
import javax.annotation.*;
import java.io.*;
import java.util.Date;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import static com.google.common.base.Preconditions.*;
/**
* A class that handles atomic and optionally delayed writing of the wallet file to disk. In future: backups too.
* It can be useful to delay writing of a wallet 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 WalletFiles {
private static final Logger log = LoggerFactory.getLogger(WalletFiles.class);
private final Wallet wallet;
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 wallet 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 wallet 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 wallet file to disk. Note the initial wallet state isn't
* saved automatically. The {@link Wallet} calls {@link #saveNow()} or {@link #saveLater()} as wallet state changes,
* depending on the urgency of the changes.
*/
public WalletFiles(final Wallet wallet, 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("Wallet autosave thread", Thread.MIN_PRIORITY));
this.executor.setKeepAliveTime(5, TimeUnit.SECONDS);
this.executor.allowCoreThreadTimeOut(true);
this.executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
this.wallet = checkNotNull(wallet);
// 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;
}
Date lastBlockSeenTime = wallet.getLastBlockSeenTime();
log.info("Background saving wallet; last seen block is height {}, date {}, hash {}",
wallet.getLastBlockSeenHeight(),
lastBlockSeenTime != null ? Utils.dateTimeFormat(lastBlockSeenTime) : "unknown",
wallet.getLastBlockSeenHash());
saveNowInternal();
return null;
}
};
}
/** Get the {@link Wallet} this {@link WalletFiles} is managing. */
public Wallet getWallet() {
return wallet;
}
/**
* The given listener will be called on the autosave thread before and after the wallet is saved to disk.
*/
public void setListener(@Nonnull Listener listener) {
this.vListener = checkNotNull(listener);
}
/** Actually write the wallet 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 wallet is locked whilst saving, so we can have two saves in flight
// but they will serialize (using different temp files).
if (executor.isShutdown())
return;
Date lastBlockSeenTime = wallet.getLastBlockSeenTime();
log.info("Saving wallet; last seen block is height {}, date {}, hash {}", wallet.getLastBlockSeenHeight(),
lastBlockSeenTime != null ? Utils.dateTimeFormat(lastBlockSeenTime) : "unknown",
wallet.getLastBlockSeenHash());
saveNowInternal();
}
private void saveNowInternal() throws IOException {
final Stopwatch watch = Stopwatch.createStarted();
File directory = file.getAbsoluteFile().getParentFile();
File temp = File.createTempFile("wallet", null, directory);
final Listener listener = vListener;
if (listener != null)
listener.onBeforeAutoSave(temp);
wallet.saveToFile(temp, file);
if (listener != null)
listener.onAfterAutoSave(file);
watch.stop();
log.info("Save completed in {}", watch);
}
/** Queues up a save in the background. Useful for not very important wallet 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);
}
}
}
