| /* |
| * Copyright © 2012-2014 Cask Data, Inc. |
| * |
| * 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 |
| * |
| * 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 co.cask.tephra.persist; |
| |
| import co.cask.tephra.metrics.MetricsCollector; |
| import com.google.common.base.Throwables; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.fs.FileStatus; |
| import org.apache.hadoop.fs.FileSystem; |
| import org.apache.hadoop.fs.Path; |
| import org.apache.hadoop.io.LongWritable; |
| import org.apache.hadoop.io.SequenceFile; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import java.io.EOFException; |
| import java.io.IOException; |
| |
| /** |
| * Allows reading from and writing to a transaction write-ahead log stored in HDFS. |
| */ |
| public class HDFSTransactionLog extends AbstractTransactionLog { |
| private static final Logger LOG = LoggerFactory.getLogger(HDFSTransactionLog.class); |
| |
| private final FileSystem fs; |
| private final Configuration hConf; |
| private final Path logPath; |
| |
| /** |
| * Creates a new HDFS-backed write-ahead log for storing transaction state. |
| * @param fs Open FileSystem instance for opening log files in HDFS. |
| * @param hConf HDFS cluster configuration. |
| * @param logPath Path to the log file. |
| */ |
| public HDFSTransactionLog(final FileSystem fs, final Configuration hConf, |
| final Path logPath, long timestamp, MetricsCollector metricsCollector) { |
| super(timestamp, metricsCollector); |
| this.fs = fs; |
| this.hConf = hConf; |
| this.logPath = logPath; |
| } |
| |
| @Override |
| protected TransactionLogWriter createWriter() throws IOException { |
| return new LogWriter(fs, hConf, logPath); |
| } |
| |
| @Override |
| public String getName() { |
| return logPath.getName(); |
| } |
| |
| @Override |
| public TransactionLogReader getReader() throws IOException { |
| FileStatus status = fs.getFileStatus(logPath); |
| long length = status.getLen(); |
| |
| LogReader reader = null; |
| // check if this file needs to be recovered due to failure |
| // Check for possibly empty file. With appends, currently Hadoop reports a |
| // zero length even if the file has been sync'd. Revisit if HDFS-376 or |
| // HDFS-878 is committed. |
| if (length <= 0) { |
| LOG.warn("File " + logPath + " might be still open, length is 0"); |
| } |
| |
| try { |
| HDFSUtil hdfsUtil = new HDFSUtil(); |
| hdfsUtil.recoverFileLease(fs, logPath, hConf); |
| try { |
| FileStatus newStatus = fs.getFileStatus(logPath); |
| LOG.info("New file size for " + logPath + " is " + newStatus.getLen()); |
| SequenceFile.Reader fileReader = new SequenceFile.Reader(fs, logPath, hConf); |
| reader = new LogReader(fileReader); |
| } catch (EOFException e) { |
| if (length <= 0) { |
| // TODO should we ignore an empty, not-last log file if skip.errors |
| // is false? Either way, the caller should decide what to do. E.g. |
| // ignore if this is the last log in sequence. |
| // TODO is this scenario still possible if the log has been |
| // recovered (i.e. closed) |
| LOG.warn("Could not open " + logPath + " for reading. File is empty", e); |
| return null; |
| } else { |
| // EOFException being ignored |
| return null; |
| } |
| } |
| } catch (IOException e) { |
| throw e; |
| } |
| |
| return reader; |
| } |
| |
| private static final class LogWriter implements TransactionLogWriter { |
| private final SequenceFile.Writer internalWriter; |
| |
| public LogWriter(FileSystem fs, Configuration hConf, Path logPath) throws IOException { |
| // TODO: retry a few times to ride over transient failures? |
| this.internalWriter = |
| SequenceFile.createWriter(fs, hConf, logPath, LongWritable.class, TransactionEdit.class); |
| LOG.debug("Created a new TransactionLog writer for " + logPath); |
| } |
| |
| @Override |
| public void append(Entry entry) throws IOException { |
| internalWriter.append(entry.getKey(), entry.getEdit()); |
| } |
| |
| @Override |
| public void sync() throws IOException { |
| internalWriter.syncFs(); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| internalWriter.close(); |
| } |
| } |
| |
| private static final class LogReader implements TransactionLogReader { |
| |
| private boolean closed; |
| private SequenceFile.Reader reader; |
| private LongWritable key = new LongWritable(); |
| |
| public LogReader(SequenceFile.Reader reader) { |
| this.reader = reader; |
| } |
| |
| @Override |
| public TransactionEdit next() { |
| try { |
| return next(new TransactionEdit()); |
| } catch (IOException ioe) { |
| throw Throwables.propagate(ioe); |
| } |
| } |
| |
| @Override |
| public TransactionEdit next(TransactionEdit reuse) throws IOException { |
| if (closed) { |
| return null; |
| } |
| LOG.error("1111111 Position in file = {}", reader.getPosition()); |
| boolean successful = reader.next(key, reuse); |
| if (successful) { |
| return reuse; |
| } |
| return null; |
| } |
| |
| @Override |
| public void close() throws IOException { |
| if (closed) { |
| return; |
| } |
| reader.close(); |
| closed = true; |
| } |
| } |
| } |