| /** |
| * 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.hadoop.hdfs.server.namenode; |
| |
| import java.io.IOException; |
| import java.io.OutputStream; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.hdfs.protocol.HdfsConstants; |
| import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.Writer; |
| import org.apache.hadoop.io.DataOutputBuffer; |
| import org.apache.hadoop.io.IOUtils; |
| |
| import com.google.common.base.Preconditions; |
| |
| /** |
| * A double-buffer for edits. New edits are written into the first buffer |
| * while the second is available to be flushed. Each time the double-buffer |
| * is flushed, the two internal buffers are swapped. This allows edits |
| * to progress concurrently to flushes without allocating new buffers each |
| * time. |
| */ |
| @InterfaceAudience.Private |
| public class EditsDoubleBuffer { |
| |
| private TxnBuffer bufCurrent; // current buffer for writing |
| private TxnBuffer bufReady; // buffer ready for flushing |
| private final int initBufferSize; |
| |
| public EditsDoubleBuffer(int defaultBufferSize) { |
| initBufferSize = defaultBufferSize; |
| bufCurrent = new TxnBuffer(initBufferSize); |
| bufReady = new TxnBuffer(initBufferSize); |
| |
| } |
| |
| public void writeOp(FSEditLogOp op) throws IOException { |
| bufCurrent.writeOp(op); |
| } |
| |
| public void writeRaw(byte[] bytes, int offset, int length) throws IOException { |
| bufCurrent.write(bytes, offset, length); |
| } |
| |
| public void close() throws IOException { |
| Preconditions.checkNotNull(bufCurrent); |
| Preconditions.checkNotNull(bufReady); |
| |
| int bufSize = bufCurrent.size(); |
| if (bufSize != 0) { |
| throw new IOException("FSEditStream has " + bufSize |
| + " bytes still to be flushed and cannot be closed."); |
| } |
| |
| IOUtils.cleanup(null, bufCurrent, bufReady); |
| bufCurrent = bufReady = null; |
| } |
| |
| public void setReadyToFlush() { |
| assert isFlushed() : "previous data not flushed yet"; |
| TxnBuffer tmp = bufReady; |
| bufReady = bufCurrent; |
| bufCurrent = tmp; |
| } |
| |
| /** |
| * Writes the content of the "ready" buffer to the given output stream, |
| * and resets it. Does not swap any buffers. |
| */ |
| public void flushTo(OutputStream out) throws IOException { |
| bufReady.writeTo(out); // write data to file |
| bufReady.reset(); // erase all data in the buffer |
| } |
| |
| public boolean shouldForceSync() { |
| return bufCurrent.size() >= initBufferSize; |
| } |
| |
| DataOutputBuffer getReadyBuf() { |
| return bufReady; |
| } |
| |
| DataOutputBuffer getCurrentBuf() { |
| return bufCurrent; |
| } |
| |
| public boolean isFlushed() { |
| return bufReady.size() == 0; |
| } |
| |
| public int countBufferedBytes() { |
| return bufReady.size() + bufCurrent.size(); |
| } |
| |
| /** |
| * @return the transaction ID of the first transaction ready to be flushed |
| */ |
| public long getFirstReadyTxId() { |
| assert bufReady.firstTxId > 0; |
| return bufReady.firstTxId; |
| } |
| |
| /** |
| * @return the number of transactions that are ready to be flushed |
| */ |
| public int countReadyTxns() { |
| return bufReady.numTxns; |
| } |
| |
| /** |
| * @return the number of bytes that are ready to be flushed |
| */ |
| public int countReadyBytes() { |
| return bufReady.size(); |
| } |
| |
| private static class TxnBuffer extends DataOutputBuffer { |
| long firstTxId; |
| int numTxns; |
| private Writer writer; |
| |
| public TxnBuffer(int initBufferSize) { |
| super(initBufferSize); |
| writer = new FSEditLogOp.Writer(this); |
| reset(); |
| } |
| |
| public void writeOp(FSEditLogOp op) throws IOException { |
| if (firstTxId == HdfsConstants.INVALID_TXID) { |
| firstTxId = op.txid; |
| } else { |
| assert op.txid > firstTxId; |
| } |
| writer.writeOp(op); |
| numTxns++; |
| } |
| |
| @Override |
| public DataOutputBuffer reset() { |
| super.reset(); |
| firstTxId = HdfsConstants.INVALID_TXID; |
| numTxns = 0; |
| return this; |
| } |
| } |
| |
| } |