| /** |
| * 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.datanode.fsdataset.impl; |
| |
| import java.io.BufferedReader; |
| import java.io.File; |
| import java.io.FileInputStream; |
| import java.io.FileNotFoundException; |
| import java.io.FileOutputStream; |
| import java.io.IOException; |
| import java.io.InputStreamReader; |
| import java.io.OutputStreamWriter; |
| import java.io.PrintWriter; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| import org.apache.hadoop.hdfs.server.datanode.DataBlockScanner; |
| import org.apache.hadoop.hdfs.server.datanode.fsdataset.RollingLogs; |
| |
| import com.google.common.base.Charsets; |
| |
| class RollingLogsImpl implements RollingLogs { |
| private static final String CURR_SUFFIX = ".curr"; |
| private static final String PREV_SUFFIX = ".prev"; |
| |
| static boolean isFilePresent(String dir, String filePrefix) { |
| return new File(dir, filePrefix + CURR_SUFFIX).exists() || |
| new File(dir, filePrefix + PREV_SUFFIX).exists(); |
| } |
| |
| private final File curr; |
| private final File prev; |
| private PrintWriter out; //require synchronized access |
| |
| private final Appender appender = new Appender() { |
| @Override |
| public Appendable append(CharSequence csq) { |
| synchronized(RollingLogsImpl.this) { |
| if (out == null) { |
| throw new IllegalStateException(RollingLogsImpl.this |
| + " is not yet opened."); |
| } |
| out.print(csq); |
| out.flush(); |
| } |
| return this; |
| } |
| |
| @Override |
| public Appendable append(char c) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| @Override |
| public Appendable append(CharSequence csq, int start, int end) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| @Override |
| public void close() { |
| synchronized(RollingLogsImpl.this) { |
| if (out != null) { |
| out.close(); |
| out = null; |
| } |
| } |
| } |
| }; |
| |
| |
| private final AtomicInteger numReaders = new AtomicInteger(); |
| |
| RollingLogsImpl(String dir, String filePrefix) throws FileNotFoundException{ |
| curr = new File(dir, filePrefix + CURR_SUFFIX); |
| prev = new File(dir, filePrefix + PREV_SUFFIX); |
| out = new PrintWriter(new OutputStreamWriter(new FileOutputStream( |
| curr, true), Charsets.UTF_8)); |
| } |
| |
| @Override |
| public Reader iterator(boolean skipPrevFile) throws IOException { |
| numReaders.incrementAndGet(); |
| return new Reader(skipPrevFile); |
| } |
| |
| @Override |
| public Appender appender() { |
| return appender; |
| } |
| |
| @Override |
| public boolean roll() throws IOException { |
| if (numReaders.get() > 0) { |
| return false; |
| } |
| if (!prev.delete() && prev.exists()) { |
| throw new IOException("Failed to delete " + prev); |
| } |
| |
| synchronized(this) { |
| appender.close(); |
| final boolean renamed = curr.renameTo(prev); |
| out = new PrintWriter(new OutputStreamWriter(new FileOutputStream( |
| curr, true), Charsets.UTF_8)); |
| if (!renamed) { |
| throw new IOException("Failed to rename " + curr + " to " + prev); |
| } |
| } |
| return true; |
| } |
| |
| @Override |
| public String toString() { |
| return curr.toString(); |
| } |
| |
| /** |
| * This is used to read the lines in order. |
| * If the data is not read completely (i.e, untill hasNext() returns |
| * false), it needs to be explicitly |
| */ |
| private class Reader implements RollingLogs.LineIterator { |
| private File file; |
| private File lastReadFile; |
| private BufferedReader reader; |
| private String line; |
| private boolean closed = false; |
| |
| private Reader(boolean skipPrevFile) throws IOException { |
| reader = null; |
| file = skipPrevFile? curr : prev; |
| readNext(); |
| } |
| |
| @Override |
| public boolean isPrevious() { |
| return file == prev; |
| } |
| |
| @Override |
| public boolean isLastReadFromPrevious() { |
| return lastReadFile == prev; |
| } |
| |
| private boolean openFile() throws IOException { |
| |
| for(int i=0; i<2; i++) { |
| if (reader != null || i > 0) { |
| // move to next file |
| file = isPrevious()? curr : null; |
| } |
| if (file == null) { |
| return false; |
| } |
| if (file.exists()) { |
| break; |
| } |
| } |
| |
| if (reader != null ) { |
| reader.close(); |
| reader = null; |
| } |
| |
| reader = new BufferedReader(new InputStreamReader(new FileInputStream( |
| file), Charsets.UTF_8)); |
| return true; |
| } |
| |
| // read next line if possible. |
| private void readNext() throws IOException { |
| line = null; |
| try { |
| if (reader != null && (line = reader.readLine()) != null) { |
| return; |
| } |
| // move to the next file. |
| if (openFile()) { |
| readNext(); |
| } |
| } finally { |
| if (!hasNext()) { |
| close(); |
| } |
| } |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return line != null; |
| } |
| |
| @Override |
| public String next() { |
| String curLine = line; |
| try { |
| lastReadFile = file; |
| readNext(); |
| } catch (IOException e) { |
| DataBlockScanner.LOG.warn("Failed to read next line.", e); |
| } |
| return curLine; |
| } |
| |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| if (!closed) { |
| try { |
| if (reader != null) { |
| reader.close(); |
| } |
| } finally { |
| file = null; |
| reader = null; |
| closed = true; |
| final int n = numReaders.decrementAndGet(); |
| assert(n >= 0); |
| } |
| } |
| } |
| } |
| } |