jetbrains.exodus.io.SharedMappedFilesCache Maven / Gradle / Ivy
/**
* Copyright 2010 - 2022 JetBrains s.r.o.
*
* 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
*
* https://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 jetbrains.exodus.io;
import jetbrains.exodus.ExodusException;
import jetbrains.exodus.core.dataStructures.hash.LinkedHashMap;
import jetbrains.exodus.system.OperatingSystem;
import jetbrains.exodus.util.SharedRandomAccessFile;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentLinkedQueue;
public final class SharedMappedFilesCache {
private static final Object syncObject = new Object();
@Nullable
private static volatile SharedMappedFilesCache theCache = null;
private final long freePhysicalMemoryThreshold;
private final ConcurrentLinkedQueue obsoleteQueue;
private final LinkedHashMap cache;
private SharedMappedFilesCache(final long freePhysicalMemoryThreshold) {
this.freePhysicalMemoryThreshold = freePhysicalMemoryThreshold;
obsoleteQueue = new ConcurrentLinkedQueue<>();
cache = new LinkedHashMap() {
@Override
protected boolean removeEldestEntry(Map.Entry eldest) {
return isOSOverloaded();
}
@Override
public SharedMappedByteBuffer remove(Object key) {
final SharedMappedByteBuffer obsolete = super.remove(key);
if (obsolete != null) {
obsoleteQueue.offer(obsolete);
}
return obsolete;
}
};
}
static void createInstance(final long freePhysicalMemoryThreshold) {
if (theCache == null) {
synchronized (syncObject) {
if (theCache == null) {
theCache = new SharedMappedFilesCache(freePhysicalMemoryThreshold);
}
}
}
}
@NotNull
static SharedMappedFilesCache getInstance() {
SharedMappedFilesCache result = theCache;
if (result == null) {
throw new ExodusException("SharedMappedFilesCache instance should be created explicitly");
}
return result;
}
/**
* For tests only!!!
*/
public static void invalidate() {
final SharedMappedFilesCache oldCache;
synchronized (syncObject) {
oldCache = SharedMappedFilesCache.theCache;
SharedMappedFilesCache.theCache = null;
}
if (oldCache != null) {
for (final SharedMappedByteBuffer buffer : oldCache.cache.values()) {
buffer.close();
}
}
}
@NotNull
SharedMappedByteBuffer getFileBuffer(@NotNull final SharedRandomAccessFile file) throws IOException {
try {
SharedMappedByteBuffer result;
final File key = file.getFile();
synchronized (cache) {
result = cache.get(key);
if (result != null) {
// we do employ() in the critical section intentionally, in order to avoid possible
// (though rather theoretical) race with closing this buffer when it becomes obsolete
result.employ();
return result;
}
}
result = new SharedMappedByteBuffer(file);
result.employ();
final SharedMappedByteBuffer obsolete;
synchronized (cache) {
obsolete = cache.put(key, result);
}
if (obsolete != null) {
obsoleteQueue.offer(obsolete);
}
return result;
} finally {
freeObsoleteBuffers();
}
}
void removeFileBuffer(@NotNull final File file) {
try {
final SharedMappedByteBuffer obsolete;
synchronized (cache) {
obsolete = cache.remove(file);
}
if (obsolete != null) {
obsoleteQueue.offer(obsolete);
}
} finally {
freeObsoleteBuffers();
}
}
void removeDirectory(@NotNull final File dir) {
try {
final List result = new ArrayList<>();
final List obsoleteFiles = new ArrayList<>();
synchronized (cache) {
for (File file : cache.keySet()) {
if (file.getParentFile().equals(dir)) {
obsoleteFiles.add(file);
result.add(cache.get(file));
}
}
for (final File file : obsoleteFiles) {
cache.remove(file);
}
}
for (final SharedMappedByteBuffer obsolete : result) {
obsoleteQueue.offer(obsolete);
}
} finally {
freeObsoleteBuffers();
}
}
private void freeObsoleteBuffers() {
SharedMappedByteBuffer obsolete;
while (true) {
while ((obsolete = obsoleteQueue.poll()) != null) {
obsolete.close();
}
if (!isOSOverloaded()) {
break;
}
synchronized (cache) {
if (cache.size() == 0) {
break;
}
cache.removeEldest();
}
}
}
private boolean isOSOverloaded() {
return OperatingSystem.getFreePhysicalMemorySize() < freePhysicalMemoryThreshold;
}
}