org.apache.druid.data.input.impl.AbstractTextFilesFirehoseFactory.java Source code

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Here is the source code for org.apache.druid.data.input.impl.AbstractTextFilesFirehoseFactory.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.druid.data.input.impl;

import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.LineIterator;
import org.apache.druid.data.input.FiniteFirehoseFactory;
import org.apache.druid.data.input.Firehose;
import org.apache.druid.data.input.InputSplit;
import org.apache.druid.java.util.common.logger.Logger;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.stream.Stream;

/**
 * This is an abstract class for firehose factory for making firehoses reading text files.
 * It provides an unified {@link #connect(StringInputRowParser, File)} implementation for its subclasses.
 *
 * @param <T> object type representing input data
 */
public abstract class AbstractTextFilesFirehoseFactory<T>
        implements FiniteFirehoseFactory<StringInputRowParser, T> {
    private static final Logger LOG = new Logger(AbstractTextFilesFirehoseFactory.class);

    private List<T> objects;

    @Override
    public Firehose connect(StringInputRowParser firehoseParser, File temporaryDirectory) throws IOException {
        initializeObjectsIfNeeded();
        final Iterator<T> iterator = objects.iterator();
        return new FileIteratingFirehose(new Iterator<LineIterator>() {
            @Override
            public boolean hasNext() {
                return iterator.hasNext();
            }

            @Override
            public LineIterator next() {
                if (!hasNext()) {
                    throw new NoSuchElementException();
                }
                final T object = iterator.next();
                try {
                    return IOUtils.lineIterator(wrapObjectStream(object, openObjectStream(object)),
                            StandardCharsets.UTF_8);
                } catch (Exception e) {
                    LOG.error(e, "Exception reading object[%s]", object);
                    throw Throwables.propagate(e);
                }
            }
        }, firehoseParser);
    }

    protected void initializeObjectsIfNeeded() throws IOException {
        if (objects == null) {
            objects = ImmutableList.copyOf(Preconditions.checkNotNull(initObjects(), "initObjects"));
        }
    }

    public List<T> getObjects() {
        return objects;
    }

    @Override
    public Stream<InputSplit<T>> getSplits() throws IOException {
        initializeObjectsIfNeeded();
        return getObjects().stream().map(InputSplit::new);
    }

    @Override
    public int getNumSplits() throws IOException {
        initializeObjectsIfNeeded();
        return getObjects().size();
    }

    /**
     * Initialize objects to be read by this firehose.  Since firehose factories are constructed whenever
     * org.apache.druid.indexing.common.task.Task objects are deserialized, actual initialization of objects is deferred
     * until {@link #connect(StringInputRowParser, File)} is called.
     *
     * @return a collection of initialized objects.
     */
    protected abstract Collection<T> initObjects() throws IOException;

    /**
     * Open an input stream from the given object.  If the object is compressed, this method should return a byte stream
     * as it is compressed.  The object compression should be handled in {@link #wrapObjectStream(Object, InputStream)}.
     *
     * @param object an object to be read
     *
     * @return an input stream for the object
     */
    protected abstract InputStream openObjectStream(T object) throws IOException;

    /**
     * Wrap the given input stream if needed.  The decompression logic should be applied to the given stream if the object
     * is compressed.
     *
     * @param object an input object
     * @param stream a stream for the object
     * @return an wrapped input stream
     */
    protected abstract InputStream wrapObjectStream(T object, InputStream stream) throws IOException;
}