org.apache.beam.sdk.util.FilePatternMatchingShardedFile.java Source code

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Here is the source code for org.apache.beam.sdk.util.FilePatternMatchingShardedFile.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.beam.sdk.util;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Strings;
import com.google.common.collect.Lists;
import com.google.common.io.CharStreams;
import java.io.IOException;
import java.io.Reader;
import java.nio.channels.Channels;
import java.nio.charset.StandardCharsets;
import java.util.Collection;
import java.util.List;
import java.util.stream.Collectors;
import org.apache.beam.sdk.io.FileSystems;
import org.apache.beam.sdk.io.fs.MatchResult.Metadata;
import org.apache.beam.sdk.io.fs.ResourceId;
import org.joda.time.Duration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A sharded file which matches a given file pattern. Note that the file pattern must match at least
 * one file.
 *
 * <p>Note that file matching should only occur once the file system is in a stable state and
 * guaranteed to provide a consistent result during file pattern matching.
 */
public class FilePatternMatchingShardedFile implements ShardedFile {

    private static final Logger LOG = LoggerFactory.getLogger(FilePatternMatchingShardedFile.class);

    private static final int MAX_READ_RETRIES = 4;
    private static final Duration DEFAULT_SLEEP_DURATION = Duration.standardSeconds(10L);
    static final FluentBackoff BACK_OFF_FACTORY = FluentBackoff.DEFAULT.withInitialBackoff(DEFAULT_SLEEP_DURATION)
            .withMaxRetries(MAX_READ_RETRIES);

    private final String filePattern;

    /**
     * Constructs an {@link FilePatternMatchingShardedFile} for the given file pattern. Note that the
     * file pattern must match at least one file.
     *
     * <p>Note that file matching should only occur once the file system is in a stable state and
     * guaranteed to provide a consistent result during file pattern matching.
     */
    public FilePatternMatchingShardedFile(String filePattern) {
        checkArgument(!Strings.isNullOrEmpty(filePattern), "Expected valid file path, but received %s",
                filePattern);
        this.filePattern = filePattern;
    }

    /** Discovers all shards of this file using the provided {@link Sleeper} and {@link BackOff}. */
    @Override
    public List<String> readFilesWithRetries(Sleeper sleeper, BackOff backOff)
            throws IOException, InterruptedException {
        IOException lastException = null;

        do {
            try {
                Collection<Metadata> files = FileSystems.match(filePattern).metadata();
                LOG.debug("Found file(s) {} by matching the path: {}", files.stream().map(Metadata::resourceId)
                        .map(ResourceId::getFilename).collect(Collectors.joining(",")), filePattern);
                if (files.isEmpty()) {
                    continue;
                }
                // Read data from file paths
                return readLines(files);
            } catch (IOException e) {
                // Ignore and retry
                lastException = e;
                LOG.warn("Error in file reading. Ignore and retry.");
            }
        } while (BackOffUtils.next(sleeper, backOff));
        // Failed after max retries
        throw new IOException(String.format("Unable to read file(s) after retrying %d times", MAX_READ_RETRIES),
                lastException);
    }

    /** Discovers all shards of this file. */
    public List<String> readFilesWithRetries() throws IOException, InterruptedException {
        return readFilesWithRetries(Sleeper.DEFAULT, BACK_OFF_FACTORY.backoff());
    }

    @Override
    public String toString() {
        return String.format("sharded file matching pattern: %s", filePattern);
    }

    /**
     * Reads all the lines of all the files.
     *
     * <p>Not suitable for use except in testing of small data, since the data size may be far more
     * than can be reasonably processed serially, in-memory, by a single thread.
     */
    @VisibleForTesting
    List<String> readLines(Collection<Metadata> files) throws IOException {
        List<String> allLines = Lists.newArrayList();
        int i = 1;
        for (Metadata file : files) {
            try (Reader reader = Channels.newReader(FileSystems.open(file.resourceId()),
                    StandardCharsets.UTF_8.name())) {
                List<String> lines = CharStreams.readLines(reader);
                allLines.addAll(lines);
                LOG.debug("[{} of {}] Read {} lines from file: {}", i, files.size(), lines.size(), file);
            }
            i++;
        }
        return allLines;
    }
}