| /** |
| * 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 |
| * <p/> |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * <p/> |
| * 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.tez.dag.history.logging.proto; |
| |
| import java.io.Closeable; |
| import java.io.IOException; |
| |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.fs.Path; |
| import org.apache.hadoop.io.NullWritable; |
| import org.apache.hadoop.io.SequenceFile.Reader; |
| |
| import com.google.protobuf.MessageLite; |
| import com.google.protobuf.Parser; |
| |
| public class ProtoMessageReader<T extends MessageLite> implements Closeable { |
| private final Path filePath; |
| private final Reader reader; |
| private final ProtoMessageWritable<T> writable; |
| |
| public ProtoMessageReader(Configuration conf, Path filePath, Parser<T> parser) throws IOException { |
| this.filePath = filePath; |
| // The writer does not flush the length during hflush. Using length options lets us read |
| // past length in the FileStatus but it will throw EOFException during a read instead |
| // of returning null. |
| this.reader = new Reader(conf, Reader.file(filePath), Reader.length(Long.MAX_VALUE)); |
| this.writable = new ProtoMessageWritable<>(parser); |
| } |
| |
| public Path getFilePath() { |
| return filePath; |
| } |
| |
| public void setOffset(long offset) throws IOException { |
| reader.seek(offset); |
| } |
| |
| public long getOffset() throws IOException { |
| return reader.getPosition(); |
| } |
| |
| public T readEvent() throws IOException { |
| if (!reader.next(NullWritable.get(), writable)) { |
| return null; |
| } |
| return writable.getMessage(); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| reader.close(); |
| } |
| } |