content: /*
   * 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
   *
   *     https://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.trevni.avro.mapreduce;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.nio.charset.StandardCharsets;
  import java.util.Map.Entry;
  
  import org.apache.avro.Schema;
  import org.apache.avro.reflect.ReflectData;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.mapreduce.RecordWriter;
  import org.apache.hadoop.mapreduce.TaskAttemptContext;
  import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
  import org.apache.trevni.ColumnFileMetaData;
  import org.apache.trevni.avro.AvroColumnWriter;
  
  /**
   * Abstract base class for <code>RecordWriter</code>s that writes Trevni
   * container files.
   *
   * @param <K> The type of key the record writer should generate.
   * @param <V> The type of value the record wrtier should generate.
   * @param <T> The type of the entries within the Trevni container file being
   *            written.
   */
  public abstract class AvroTrevniRecordWriterBase<K, V, T> extends RecordWriter<K, V> {
  
    /** trevni file extension */
    public final static String EXT = ".trv";
  
    /** prefix of job configs that we care about */
    public static final String META_PREFIX = "trevni.meta.";
  
    /**
     * Counter that increments as new trevni files are create because the current
     * file has exceeded the block size
     */
    protected int part = 0;
  
    /** Trevni file writer */
    protected AvroColumnWriter<T> writer;
  
    /** This will be a unique directory linked to the task */
    final Path dirPath;
  
    /** HDFS object */
    final FileSystem fs;
  
    /** Current configured blocksize */
    final long blockSize;
  
    /** Provided avro schema from the context */
    protected Schema schema;
  
    /** meta data to be stored in the output file. */
    protected ColumnFileMetaData meta;
  
    /**
     * Constructor.
     * 
     * @param context The TaskAttempContext to supply the writer with information
     *                form the job configuration
     */
    public AvroTrevniRecordWriterBase(TaskAttemptContext context) throws IOException {
  
      schema = initSchema(context);
      meta = filterMetadata(context.getConfiguration());
      writer = new AvroColumnWriter<>(schema, meta, ReflectData.get());
  
      Path outputPath = FileOutputFormat.getOutputPath(context);
  
      String dir = FileOutputFormat.getUniqueFile(context, "part", "");
      dirPath = new Path(outputPath.toString() + "/" + dir);
      fs = dirPath.getFileSystem(context.getConfiguration());
      fs.mkdirs(dirPath);
  
      blockSize = fs.getDefaultBlockSize(dirPath);
    }
  
    /**
     * Use the task context to construct a schema for writing
     * 
     * @throws IOException
     */
    abstract protected Schema initSchema(TaskAttemptContext context);
  
    /**
     * A Trevni flush will close the current file and prep a new writer
     * 
     * @throws IOException
     */
    public void flush() throws IOException {
      try (OutputStream out = fs.create(new Path(dirPath, "part-" + (part++) + EXT))) {
        writer.writeTo(out);
      }
      writer = new AvroColumnWriter<>(schema, meta, ReflectData.get());
    }
  
    /** {@inheritDoc} */
    @Override
    public void close(TaskAttemptContext arg0) throws IOException, InterruptedException {
      flush();
    }
  
    static ColumnFileMetaData filterMetadata(final Configuration configuration) {
      final ColumnFileMetaData meta = new ColumnFileMetaData();
  
      for (Entry<String, String> confEntry : configuration) {
        if (confEntry.getKey().startsWith(META_PREFIX))
          meta.put(confEntry.getKey().substring(META_PREFIX.length()),
              confEntry.getValue().getBytes(StandardCharsets.UTF_8));
      }
  
      return meta;
    }
  }
  