content: /*
   * 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 org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  
  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.annotations.Internal;
  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.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Strings;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Lists;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.io.CharStreams;
  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.
   */
  @Internal
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  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;
    }
  }
  