| /** |
| * 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.io.Writable; |
| |
| /** |
| * A generic abstract class to support journaling of edits logs into |
| * a persistent storage. |
| */ |
| abstract class EditLogOutputStream extends OutputStream |
| implements JournalStream { |
| // these are statistics counters |
| private long numSync; // number of sync(s) to disk |
| private long totalTimeSync; // total time to sync |
| |
| EditLogOutputStream() throws IOException { |
| numSync = totalTimeSync = 0; |
| } |
| |
| /** {@inheritDoc} */ |
| abstract public void write(int b) throws IOException; |
| |
| /** |
| * Write edits log record into the stream. |
| * The record is represented by operation name and |
| * an array of Writable arguments. |
| * |
| * @param op operation |
| * @param writables array of Writable arguments |
| * @throws IOException |
| */ |
| abstract void write(byte op, Writable ... writables) throws IOException; |
| |
| /** |
| * Create and initialize underlying persistent edits log storage. |
| * |
| * @throws IOException |
| */ |
| abstract void create() throws IOException; |
| |
| /** {@inheritDoc} */ |
| abstract public void close() throws IOException; |
| |
| /** |
| * All data that has been written to the stream so far will be flushed. |
| * New data can be still written to the stream while flushing is performed. |
| */ |
| abstract void setReadyToFlush() throws IOException; |
| |
| /** |
| * Flush and sync all data that is ready to be flush |
| * {@link #setReadyToFlush()} into underlying persistent store. |
| * @throws IOException |
| */ |
| abstract protected void flushAndSync() throws IOException; |
| |
| /** |
| * Flush data to persistent store. |
| * Collect sync metrics. |
| */ |
| public void flush() throws IOException { |
| numSync++; |
| long start = FSNamesystem.now(); |
| flushAndSync(); |
| long end = FSNamesystem.now(); |
| totalTimeSync += (end - start); |
| } |
| |
| /** |
| * Return the size of the current edits log. |
| * Length is used to check when it is large enough to start a checkpoint. |
| */ |
| abstract long length() throws IOException; |
| |
| boolean isOperationSupported(byte op) { |
| return true; |
| } |
| |
| /** |
| * Return total time spent in {@link #flushAndSync()} |
| */ |
| long getTotalSyncTime() { |
| return totalTimeSync; |
| } |
| |
| /** |
| * Return number of calls to {@link #flushAndSync()} |
| */ |
| long getNumSync() { |
| return numSync; |
| } |
| |
| @Override // Object |
| public String toString() { |
| return getName(); |
| } |
| } |