IgfsRecordResolver.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.ignite.igfs.mapreduce;

import java.io.IOException;
import java.io.Serializable;
import org.apache.ignite.IgniteException;
import org.apache.ignite.IgniteFileSystem;
import org.apache.ignite.igfs.IgfsInputStream;
import org.jetbrains.annotations.Nullable;

/**
 * IGFS record resolver. When {@link IgfsTask} is split into {@link IgfsJob}s each produced job will obtain
 * {@link IgfsFileRange} based on file data location. Record resolver is invoked in each job before actual
 * execution in order to adjust record boundaries in a way consistent with user data.
 * <p>
 * E.g., you may want to split your task into jobs so that each job process zero, one or several lines from that file.
 * But file is split into ranges based on block locations, not new line boundaries. Using convenient record resolver
 * you can adjust job range so that it covers the whole line(s).
 * <p>
 * The following record resolvers are available out of the box:
 * <ul>
 *     <li>{@link org.apache.ignite.igfs.mapreduce.records.IgfsFixedLengthRecordResolver}</li>
 *     <li>{@link org.apache.ignite.igfs.mapreduce.records.IgfsByteDelimiterRecordResolver}</li>
 *     <li>{@link org.apache.ignite.igfs.mapreduce.records.IgfsStringDelimiterRecordResolver}</li>
 *     <li>{@link org.apache.ignite.igfs.mapreduce.records.IgfsNewLineRecordResolver}</li>
 * </ul>
 */
public interface IgfsRecordResolver extends Serializable {
    /**
     * Adjusts record start offset and length.
     *
     * @param fs IGFS instance to use.
     * @param stream Input stream for split file.
     * @param suggestedRecord Suggested file system record.
     * @return New adjusted record. If this method returns {@code null}, original record is ignored.
     * @throws IgniteException If resolve failed.
     * @throws IOException If resolve failed.
     */
    @Nullable public IgfsFileRange resolveRecords(IgniteFileSystem fs, IgfsInputStream stream,
        IgfsFileRange suggestedRecord) throws IgniteException, IOException;
}