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/*
* Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* 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.amazon.carbonado.cursor;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentHashMap;
/**
* Used internally by {@link MergeSortBuffer}.
*
* @author Brian S O'Neill
*/
class WorkFilePool {
private static final String cTempDir = System.getProperty("java.io.tmpdir");
private static final ConcurrentMap<String, WorkFilePool> cPools =
new ConcurrentHashMap<String, WorkFilePool>();
/**
* @param tempDir directory to store temp files for merging, or null for default
*/
static WorkFilePool getInstance(String tempDir) {
// This method uses ConcurrentMap features to eliminate the need to
// ever synchronize access, since this method may be called frequently.
if (tempDir == null) {
tempDir = cTempDir;
}
WorkFilePool pool = cPools.get(tempDir);
if (pool != null) {
return pool;
}
String canonical;
try {
canonical = new File(tempDir).getCanonicalPath();
} catch (IOException e) {
canonical = new File(tempDir).getAbsolutePath();
}
if (!canonical.equals(tempDir)) {
pool = getInstance(canonical);
cPools.putIfAbsent(tempDir, pool);
return pool;
}
pool = new WorkFilePool(new File(tempDir));
WorkFilePool existing = cPools.putIfAbsent(tempDir, pool);
if (existing == null) {
// New pool is the winner, so finish off initialization. Pool can
// be used concurrently by another thread without shutdown hook.
pool.addShutdownHook(tempDir);
} else {
pool = existing;
}
return pool;
}
private final File mTempDir;
// Work files not currently being used by any MergeSortBuffer.
private final List<RandomAccessFile> mWorkFilePool;
// Instances of MergeSortBuffer, to be notified on shutdown that they
// should close their work files.
private final Set<MergeSortBuffer<?>> mWorkFileUsers;
private Thread mShutdownHook;
/**
* @param tempDir directory to store temp files for merging, or null for default
*/
private WorkFilePool(File tempDir) {
mTempDir = tempDir;
mWorkFilePool = new ArrayList<RandomAccessFile>();
mWorkFileUsers = new HashSet<MergeSortBuffer<?>>();
}
RandomAccessFile acquireWorkFile(MergeSortBuffer<?> buffer) throws IOException {
synchronized (mWorkFileUsers) {
mWorkFileUsers.add(buffer);
}
synchronized (mWorkFilePool) {
if (mWorkFilePool.size() > 0) {
return mWorkFilePool.remove(mWorkFilePool.size() - 1);
}
}
File file = File.createTempFile("carbonado-mergesort-", null, mTempDir);
file.deleteOnExit();
return new RandomAccessFile(file, "rw");
}
void releaseWorkFiles(List<RandomAccessFile> files) {
synchronized (mWorkFilePool) {
for (RandomAccessFile raf : files) {
try {
raf.seek(0);
// Return space to file system.
raf.setLength(0);
mWorkFilePool.add(raf);
} catch (IOException e) {
// Work file is broken, discard it.
try {
raf.close();
} catch (IOException e2) {
}
}
}
}
}
void unregisterWorkFileUser(MergeSortBuffer<?> buffer) {
synchronized (mWorkFileUsers) {
mWorkFileUsers.remove(buffer);
// Only one wait condition, so okay to not call notifyAll.
mWorkFileUsers.notify();
}
}
private synchronized void addShutdownHook(String tempDir) {
if (mShutdownHook != null) {
return;
}
// Add shutdown hook to close work files so that they can be deleted.
String threadName = "MergeSortBuffer shutdown (" + tempDir + ')';
mShutdownHook = new Thread(threadName) {
@Override
public void run() {
// Notify users of work files and wait for them to close.
synchronized (mWorkFileUsers) {
for (MergeSortBuffer<?> buffer : mWorkFileUsers) {
buffer.stop();
}
final long timeout = 10000;
final long giveup = System.currentTimeMillis() + timeout;
try {
while (mWorkFileUsers.size() > 0) {
long now = System.currentTimeMillis();
if (now < giveup) {
mWorkFileUsers.wait(giveup - now);
} else {
break;
}
}
} catch (InterruptedException e) {
}
}
synchronized (mWorkFilePool) {
for (RandomAccessFile raf : mWorkFilePool) {
try {
raf.close();
} catch (IOException e) {
}
}
mWorkFilePool.clear();
}
}
};
Runtime.getRuntime().addShutdownHook(mShutdownHook);
}
}
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