| /** |
| * |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.bookkeeper.bookie; |
| |
| import java.io.File; |
| import java.io.IOException; |
| import java.io.UncheckedIOException; |
| import java.util.concurrent.atomic.AtomicInteger; |
| import java.util.concurrent.locks.ReentrantReadWriteLock; |
| import lombok.extern.slf4j.Slf4j; |
| import org.apache.bookkeeper.util.collections.ConcurrentLongHashMap; |
| |
| @Slf4j |
| class FileInfoBackingCache { |
| static final int DEAD_REF = -0xdead; |
| |
| final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(); |
| final ConcurrentLongHashMap<CachedFileInfo> fileInfos = new ConcurrentLongHashMap<>(); |
| final FileLoader fileLoader; |
| final int fileInfoVersionToWrite; |
| |
| FileInfoBackingCache(FileLoader fileLoader, int fileInfoVersionToWrite) { |
| this.fileLoader = fileLoader; |
| this.fileInfoVersionToWrite = fileInfoVersionToWrite; |
| } |
| |
| /** |
| * This method should be under `lock` of FileInfoBackingCache. |
| */ |
| private static CachedFileInfo tryRetainFileInfo(CachedFileInfo fi) throws IOException { |
| boolean retained = fi.tryRetain(); |
| if (!retained) { |
| throw new IOException("FileInfo " + fi + " is already marked dead"); |
| } else if (fi.isDeleted()) { |
| throw new Bookie.NoLedgerException(fi.ledgerId); |
| } |
| return fi; |
| } |
| |
| CachedFileInfo loadFileInfo(long ledgerId, byte[] masterKey) throws IOException { |
| lock.readLock().lock(); |
| try { |
| CachedFileInfo fi = fileInfos.get(ledgerId); |
| if (fi != null) { |
| // tryRetain only fails if #markDead() has been called |
| // on fi. This is only called from within the write lock, |
| // and if it is called (and succeeds) the fi will have been |
| // removed from fileInfos at the same time, so we should not |
| // have been able to get a reference to it here. |
| // The caller of loadFileInfo owns the refence, and is |
| // responsible for calling the corresponding #release(). |
| return tryRetainFileInfo(fi); |
| } |
| } finally { |
| lock.readLock().unlock(); |
| } |
| |
| File backingFile = fileLoader.load(ledgerId, masterKey != null); |
| CachedFileInfo newFi = new CachedFileInfo(ledgerId, backingFile, masterKey); |
| |
| // else FileInfo not found, create it under write lock |
| lock.writeLock().lock(); |
| try { |
| CachedFileInfo fi = fileInfos.get(ledgerId); |
| if (fi != null) { |
| // someone is already putting a fileinfo here, so use the existing one and recycle the new one |
| newFi.recycle(); |
| } else { |
| fileInfos.put(ledgerId, newFi); |
| fi = newFi; |
| } |
| |
| // see comment above for why we assert |
| return tryRetainFileInfo(fi); |
| } finally { |
| lock.writeLock().unlock(); |
| } |
| } |
| |
| private void releaseFileInfo(long ledgerId, CachedFileInfo fileInfo) { |
| lock.writeLock().lock(); |
| try { |
| if (fileInfo.markDead()) { |
| fileInfo.close(true); |
| fileInfos.remove(ledgerId, fileInfo); |
| } |
| } catch (IOException ioe) { |
| log.error("Error evicting file info({}) for ledger {} from backing cache", |
| fileInfo, ledgerId, ioe); |
| } finally { |
| lock.writeLock().unlock(); |
| } |
| } |
| |
| void closeAllWithoutFlushing() throws IOException { |
| try { |
| fileInfos.forEach((key, fileInfo) -> { |
| try { |
| fileInfo.close(false); |
| } catch (IOException e) { |
| throw new UncheckedIOException(e); |
| } |
| }); |
| } catch (UncheckedIOException uioe) { |
| throw uioe.getCause(); |
| } |
| } |
| |
| class CachedFileInfo extends FileInfo { |
| final long ledgerId; |
| final AtomicInteger refCount; |
| |
| CachedFileInfo(long ledgerId, File lf, byte[] masterKey) throws IOException { |
| super(lf, masterKey, fileInfoVersionToWrite); |
| this.ledgerId = ledgerId; |
| this.refCount = new AtomicInteger(0); |
| } |
| |
| /** |
| * Mark this fileinfo as dead. We can only mark a fileinfo as |
| * dead if noone currently holds a reference to it. |
| * |
| * @return true if we marked as dead, false otherwise |
| */ |
| private boolean markDead() { |
| return refCount.compareAndSet(0, DEAD_REF); |
| } |
| |
| /** |
| * Attempt to retain the file info. |
| * When a client obtains a fileinfo from a container object, |
| * but that container object may release the fileinfo before |
| * the client has a chance to call retain. In this case, the |
| * file info could be released and the destroyed before we ever |
| * get a chance to use it. |
| * |
| * <p>tryRetain avoids this problem, by doing a compare-and-swap on |
| * the reference count. If the refCount is negative, it means that |
| * the fileinfo is being cleaned up, and this fileinfo object should |
| * not be used. This works in tandem with #markDead, which will only |
| * set the refCount to negative if noone currently has it retained |
| * (i.e. the refCount is 0). |
| * |
| * @return true if we managed to increment the refcount, false otherwise |
| */ |
| boolean tryRetain() { |
| while (true) { |
| int count = refCount.get(); |
| if (count < 0) { |
| return false; |
| } else if (refCount.compareAndSet(count, count + 1)) { |
| return true; |
| } |
| } |
| } |
| |
| int getRefCount() { |
| return refCount.get(); |
| } |
| |
| void release() { |
| if (refCount.decrementAndGet() == 0) { |
| releaseFileInfo(ledgerId, this); |
| } |
| } |
| |
| @Override |
| public String toString() { |
| return "CachedFileInfo(ledger=" + ledgerId |
| + ",refCount=" + refCount.get() |
| + ",closed=" + isClosed() |
| + ",id=" + System.identityHashCode(this) + ")"; |
| } |
| } |
| |
| interface FileLoader { |
| File load(long ledgerId, boolean createIfMissing) throws IOException; |
| } |
| } |