src/main/java/org/apache/sysds/runtime/io/FrameWriterBinaryBlock.java

/*
 * 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.sysds.runtime.io;

import java.io.IOException;

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.apache.hadoop.io.SequenceFile.Writer;
import org.apache.hadoop.mapred.JobConf;
import org.apache.sysds.conf.ConfigurationManager;
import org.apache.sysds.runtime.DMLRuntimeException;
import org.apache.sysds.runtime.frame.data.FrameBlock;
import org.apache.sysds.runtime.util.HDFSTool;

/**
 * Single-threaded frame binary block writer.
 * 
 */
public class FrameWriterBinaryBlock extends FrameWriter {

	@Override
	public final void writeFrameToHDFS(FrameBlock src, String fname, long rlen, long clen)
		throws IOException, DMLRuntimeException {
		// prepare file access
		JobConf job = new JobConf(ConfigurationManager.getCachedJobConf());
		Path path = new Path(fname);

		// if the file already exists on HDFS, remove it.
		HDFSTool.deleteFileIfExistOnHDFS(fname);

		// bound check for src block
		if(src.getNumRows() > rlen || src.getNumColumns() > clen) {
			throw new IOException("Frame block [1:" + src.getNumRows() + ",1:" + src.getNumColumns() + "] "
				+ "out of overall frame range [1:" + rlen + ",1:" + clen + "].");
		}

		// write binary block to hdfs (sequential/parallel)
		writeBinaryBlockFrameToHDFS(path, job, src, rlen, clen);
	}

	protected void writeBinaryBlockFrameToHDFS(Path path, JobConf job, FrameBlock src, long rlen, long clen)
		throws IOException, DMLRuntimeException {
		FileSystem fs = IOUtilFunctions.getFileSystem(path);
		int blen = ConfigurationManager.getBlocksize();

		// sequential write to single file
		writeBinaryBlockFrameToSequenceFile(path, job, fs, src, blen, 0, (int) rlen);
		IOUtilFunctions.deleteCrcFilesFromLocalFileSystem(fs, path);
	}

	/**
	 * Internal primitive to write a block-aligned row range of a frame to a single sequence file, which is used for both
	 * single- and multi-threaded writers (for consistency).
	 * 
	 * @param path file path
	 * @param job  job configuration
	 * @param fs   file system
	 * @param src  frame block
	 * @param blen block length
	 * @param rl   lower row
	 * @param ru   upper row
	 * @throws IOException if IOException occurs
	 */
	protected static void writeBinaryBlockFrameToSequenceFile(Path path, JobConf job, FileSystem fs, FrameBlock src,
		int blen, int rl, int ru) throws IOException {
		// 1) create sequence file writer
		SequenceFile.Writer writer = SequenceFile.createWriter(job, Writer.file(path), Writer.bufferSize(4096),
			Writer.blockSize(4096), Writer.keyClass(LongWritable.class), Writer.valueClass(FrameBlock.class),
			Writer.compression(SequenceFile.CompressionType.NONE), Writer.replication((short) 1));

		final int rlen = src.getNumRows();
		final int clen = src.getNumColumns();
		try {
			// 2) reblock and write
			LongWritable index = new LongWritable();

			if(rlen <= blen) { // single block
				index.set(1);
				writer.append(index, src);
			}
			else { // multi block
				for(int bi = rl; bi < ru; bi += blen) {
					int len = Math.min(blen, rlen - bi);
					// get reuse frame block and copy subpart to block (incl meta on first)
					FrameBlock block = src.slice(bi, bi + len - 1, 0, clen - 1); // full width?
					if(bi == 0) // first block
						block.setColumnMetadata(src.getColumnMetadata());
					// append block to sequence file
					index.set(bi + 1);
					writer.append(index, block);
				}
			}
		}
		finally {
			IOUtilFunctions.closeSilently(writer);
		}
	}
}