com.uber.hoodie.common.model.HoodiePartitionMetadata Maven / Gradle / Ivy

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/*
 * Copyright (c) 2017 Uber Technologies, Inc. ([email protected])
 *
 * Licensed 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 com.uber.hoodie.common.model;

import com.uber.hoodie.exception.HoodieException;

import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;

import java.io.IOException;
import java.util.Properties;

/**
 * The metadata that goes into the meta file in each partition
 */
public class HoodiePartitionMetadata {

    public static final String HOODIE_PARTITION_METAFILE = ".hoodie_partition_metadata";
    public static final String PARTITION_DEPTH_KEY = "partitionDepth";
    public static final String COMMIT_TIME_KEY = "commitTime";

    /**
     * Contents of the metadata
     */
    private final Properties props;

    /**
     * Path to the partition, about which we have the metadata
     */
    private final Path partitionPath;

    private final FileSystem fs;

    private static Logger log = LogManager.getLogger(HoodiePartitionMetadata.class);


    /**
     * Construct metadata from existing partition
     */
    public HoodiePartitionMetadata(FileSystem fs, Path partitionPath) {
        this.fs = fs;
        this.props = new Properties();
        this.partitionPath = partitionPath;
    }

    /**
     * Construct metadata object to be written out.
     */
    public HoodiePartitionMetadata(FileSystem fs, String commitTime, Path basePath, Path partitionPath) {
        this(fs, partitionPath);
        props.setProperty(COMMIT_TIME_KEY, commitTime);
        props.setProperty(PARTITION_DEPTH_KEY, String.valueOf(partitionPath.depth() - basePath.depth()));
    }

    public int getPartitionDepth() {
        if (!props.containsKey(PARTITION_DEPTH_KEY)) {
            throw new HoodieException("Could not find partitionDepth in partition metafile");
        }
        return Integer.parseInt(props.getProperty(PARTITION_DEPTH_KEY));
    }

    /**
     * Write the metadata safely into partition atomically.
     *
     * @param taskPartitionId
     */
    public void trySave(int taskPartitionId) {
        Path tmpMetaPath = new Path(partitionPath, HoodiePartitionMetadata.HOODIE_PARTITION_METAFILE + "_" + taskPartitionId);
        Path metaPath = new Path(partitionPath, HoodiePartitionMetadata.HOODIE_PARTITION_METAFILE);
        boolean metafileExists = false;

        try {
            metafileExists = fs.exists(metaPath);
            if (!metafileExists) {
                // write to temporary file
                FSDataOutputStream os = fs.create(tmpMetaPath, true);
                props.store(os, "partition metadata");
                os.hsync();
                os.hflush();
                os.close();

                // move to actual path
                fs.rename(tmpMetaPath, metaPath);
            }
        } catch (IOException ioe) {
            log.warn("Error trying to save partition metadata (this is okay, as long as atleast 1 of these succced), " +
                    partitionPath, ioe);
        } finally {
            if (!metafileExists) {
                try {
                    // clean up tmp file, if still lying around
                    if (fs.exists(tmpMetaPath)) {
                        fs.delete(tmpMetaPath, false);
                    }
                } catch (IOException ioe) {
                    log.warn("Error trying to clean up temporary files for " + partitionPath, ioe);
                }
            }
        }
    }

    /**
     * Read out the metadata for this partition
     */
    public void readFromFS() {
        try {
            Path metaFile = new Path(partitionPath, HOODIE_PARTITION_METAFILE);
            FSDataInputStream is = fs.open(metaFile);
            props.load(is);
        } catch (IOException ioe) {
            throw new HoodieException("Error reading Hoodie partition metadata for " + partitionPath, ioe);
        }
    }

    // methods related to partition meta data
    public static boolean hasPartitionMetadata(FileSystem fs, Path partitionPath) {
        try {
            return fs.exists(new Path(partitionPath, HoodiePartitionMetadata.HOODIE_PARTITION_METAFILE));
        } catch (IOException ioe) {
            throw new HoodieException("Error checking Hoodie partition metadata for " + partitionPath, ioe);
        }
    }
}