com.sap.hana.datalake.files.utils.filewatcher.DirectoryWatcher Maven / Gradle / Ivy

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An implementation of org.apache.hadoop.fs.FileSystem targeting SAP HANA Data Lake Files.
There is a newer version: 3.0.27
// © 2023-2024 SAP SE or an SAP affiliate company. All rights reserved.
package com.sap.hana.datalake.files.utils.filewatcher;

import com.sap.hana.datalake.files.classification.InterfaceAudience;
import org.slf4j.Logger;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.util.Collections;
import java.util.List;
import java.util.Optional;

@InterfaceAudience.Private
public class DirectoryWatcher implements Runnable {

  @FunctionalInterface
  public interface EventHandler {
    void handleModifyEvent(final String fileName) throws FileWatcherException;
  }

  protected final EventHandler eventHandler;

  private final List directoriesPath;
  private final Logger log;
  private final WatchService watchService;

  public DirectoryWatcher(final String directoryPath, final Logger log, final EventHandler eventHandler) throws FileWatcherException {
    this(Collections.singletonList(directoryPath), log, eventHandler);
  }

  public DirectoryWatcher(final List directoriesPath, final Logger log, final EventHandler eventHandler) throws FileWatcherException {
    this.directoriesPath = directoriesPath;
    this.log = log;
    this.eventHandler = eventHandler;
    this.watchService = this.setupWatchService();
  }

  @Override
  public void run() {
    this.watchModifyEvents();
  }

  protected WatchService setupWatchService() throws FileWatcherException {
    try {
      final WatchService watchService = FileSystems.getDefault().newWatchService();
      final WatchEvent.Kind event = StandardWatchEventKinds.ENTRY_MODIFY;

      for (final String directoryPath : this.directoriesPath) {
        final Path dirPath = Paths.get(directoryPath).toAbsolutePath();
        dirPath.register(watchService, event);

        this.log.info("Registered the directory [{}] with the watch service for event [{}]", dirPath, event);
      }

      return watchService;
    } catch (final IOException ex) {
      final String errMsg = String.format("Error setting up the watch service for directories [%s]", this.directoriesPath);
      this.log.error(errMsg, ex);
      throw new FileWatcherException(errMsg);
    }
  }

  private void watchModifyEvents() {
    try {
      WatchKey key;

      while ((key = this.watchService.take()) != null) {
        this.handleModifyEvent(key);

        if (!key.reset()) {
          break;
        }
      }
    } catch (final InterruptedException ex) {
      this.log.error("Thread interrupt while watching events", ex);
      Thread.currentThread().interrupt();
    }
  }

  private void handleModifyEvent(final WatchKey key) {
    final Optional> modifyEvent = key.pollEvents()
            .stream()
            .filter(event -> event.kind() == StandardWatchEventKinds.ENTRY_MODIFY)
            .findFirst();

    if (!modifyEvent.isPresent()) {
      return;
    }

    final String fileName = modifyEvent.get().context().toString();

    try {
      this.eventHandler.handleModifyEvent(fileName);
    } catch (final FileWatcherException ex) {
      this.log.error(String.format("Error in handling the modify event for the file: [%s]", fileName), ex);
    }
  }
}

// © 2023-2024 SAP SE or an SAP affiliate company. All rights reserved.