org.apache.crunch.io.text.NLineFileSource.java Source code

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Here is the source code for org.apache.crunch.io.text.NLineFileSource.java

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/**
 * 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.crunch.io.text;

import java.io.IOException;

import java.util.List;

import org.apache.crunch.ReadableData;
import org.apache.crunch.impl.mr.run.RuntimeParameters;
import org.apache.crunch.io.FormatBundle;
import org.apache.crunch.io.ReadableSource;
import org.apache.crunch.io.impl.FileSourceImpl;
import org.apache.crunch.types.PType;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.lib.input.NLineInputFormat;

/**
 * A {@code Source} instance that uses the {@code NLineInputFormat}, which gives each map
 * task a fraction of the lines in a text file as input. Most useful when running simulations
 * on Hadoop, where each line represents configuration information about each simulation
 * run.
 */
public class NLineFileSource<T> extends FileSourceImpl<T> implements ReadableSource<T> {

    private static FormatBundle getBundle(int linesPerTask) {
        FormatBundle bundle = FormatBundle.forInput(NLineInputFormat.class);
        bundle.set(NLineInputFormat.LINES_PER_MAP, String.valueOf(linesPerTask));
        bundle.set(RuntimeParameters.DISABLE_COMBINE_FILE, "true");
        return bundle;
    }

    /**
     * Create a new {@code NLineFileSource} instance.
     * 
     * @param path The path to the input data, as a String
     * @param ptype The PType to use for processing the data
     * @param linesPerTask The number of lines from the input each map task will process
     */
    public NLineFileSource(String path, PType<T> ptype, int linesPerTask) {
        this(new Path(path), ptype, linesPerTask);
    }

    /**
     * Create a new {@code NLineFileSource} instance.
     *  
     * @param path The {@code Path} to the input data
     * @param ptype The PType to use for processing the data
     * @param linesPerTask The number of lines from the input each map task will process
     */
    public NLineFileSource(Path path, PType<T> ptype, int linesPerTask) {
        super(path, ptype, getBundle(linesPerTask));
    }

    /**
     * Create a new {@code NLineFileSource} instance.
     *
     * @param paths The {@code Path}s to the input data
     * @param ptype The PType to use for processing the data
     * @param linesPerTask The number of lines from the input each map task will process
     */
    public NLineFileSource(List<Path> paths, PType<T> ptype, int linesPerTask) {
        super(paths, ptype, getBundle(linesPerTask));
    }

    @Override
    public String toString() {
        return "NLine(" + pathsAsString() + ")";
    }

    @Override
    public Iterable<T> read(Configuration conf) throws IOException {
        return read(conf, new TextFileReaderFactory<T>(LineParser.forType(ptype)));
    }

    @Override
    public ReadableData<T> asReadable() {
        return new TextReadableData<T>(paths, ptype);
    }
}