Distributed File Operations

/**
 * Distributed file copy utility similar to Hadoop DistCp.
 * Usage: DistCp --input <path> --output <path> [--parallelism <n>]
 * 
 * Note: In distributed environments, HDFS paths must be provided for both input and output.
 * Local file system paths can be used when running locally.
 */
public class DistCp {
    public static final String BYTES_COPIED_CNT_NAME = "BYTES_COPIED";
    public static final String FILES_COPIED_CNT_NAME = "FILES_COPIED";
    
    public static void main(String[] args) throws Exception;
}

// Copy files with default parallelism
String[] args = {
    "--input", "/source/directory",
    "--output", "/destination/directory"
};
DistCp.main(args);

// Copy files with custom parallelism
String[] args = {
    "--input", "hdfs://source/path",
    "--output", "hdfs://destination/path", 
    "--parallelism", "20"
};
DistCp.main(args);

// Access copy statistics after execution
JobExecutionResult result = env.getLastJobExecutionResult();
Map<String, Object> accumulators = result.getAllAccumulatorResults();
Long bytesCopied = (Long) accumulators.get(DistCp.BYTES_COPIED_CNT_NAME);
Long filesCopied = (Long) accumulators.get(DistCp.FILES_COPIED_CNT_NAME);

/**
 * Represents a single file copy task with source and destination information
 */
public class FileCopyTask {
    /**
     * Creates file copy task
     * @param path Source file path
     * @param relativePath Relative path for destination
     */
    public FileCopyTask(Path path, String relativePath);
    
    /**
     * Get source file path
     * @return Source Path object
     */
    public Path getPath();
    
    /**
     * Get relative destination path
     * @return Relative path string
     */
    public String getRelativePath();
    
    @Override
    public String toString();
}

import org.apache.flink.core.fs.Path;
import org.apache.flink.examples.java.distcp.FileCopyTask;

// Create file copy task
Path sourcePath = new Path("/source/data/file1.txt");
String relativePath = "data/file1.txt";
FileCopyTask task = new FileCopyTask(sourcePath, relativePath);

// Access task properties
Path source = task.getPath();
String destination = task.getRelativePath();
System.out.println("Copy: " + source + " -> " + destination);

// Use in file discovery
List<FileCopyTask> tasks = new ArrayList<>();
// Recursively discover files and create tasks
tasks.add(new FileCopyTask(filePath, "subdir/filename.ext"));

/**
 * Input split containing a file copy task for parallel processing
 */
public class FileCopyTaskInputSplit implements InputSplit {
    /**
     * Creates input split with copy task
     * @param task File copy task to process
     * @param splitNumber Split number for identification
     */
    public FileCopyTaskInputSplit(FileCopyTask task, int splitNumber);
    
    /**
     * Get file copy task
     * @return FileCopyTask to be processed
     */
    public FileCopyTask getTask();
    
    /**
     * Get split number
     * @return Split identification number
     */
    @Override
    public int getSplitNumber();
}

// Create input split for parallel processing
FileCopyTask task = new FileCopyTask(sourcePath, relativePath);
FileCopyTaskInputSplit split = new FileCopyTaskInputSplit(task, 0);

// Access split properties
FileCopyTask copyTask = split.getTask();
int splitId = split.getSplitNumber();

// Use in input format implementation
List<FileCopyTaskInputSplit> splits = new ArrayList<>();
for (int i = 0; i < tasks.size(); i++) {
    splits.add(new FileCopyTaskInputSplit(tasks.get(i), i));
}

/**
 * Input format for distributed file copy operations.
 * Distributes file copy tasks across parallel workers.
 */
public class FileCopyTaskInputFormat extends RichInputFormat<FileCopyTask, FileCopyTaskInputSplit> {
    /**
     * Creates input format with list of copy tasks
     * @param tasks List of file copy tasks to distribute
     */
    public FileCopyTaskInputFormat(List<FileCopyTask> tasks);
    
    /**
     * Configure input format
     * @param parameters Configuration parameters
     */
    @Override
    public void configure(Configuration parameters);
    
    /**
     * Create input splits for parallel processing
     * @param minNumSplits Minimum number of splits requested
     * @return Array of input splits
     */
    @Override
    public FileCopyTaskInputSplit[] createInputSplits(int minNumSplits) throws IOException;
    
    /**
     * Get input split type information
     * @return BaseStatistics for the input
     */
    @Override
    public BaseStatistics getStatistics(BaseStatistics cachedStatistics) throws IOException;
    
    /**
     * Open input split for reading
     * @param split Input split to open
     */
    @Override
    public void open(FileCopyTaskInputSplit split) throws IOException;
    
    /**
     * Check if more records available
     * @return true if more records available, false otherwise
     */
    @Override
    public boolean reachedEnd() throws IOException;
    
    /**
     * Read next record
     * @param reuse Reusable object for record
     * @return Next FileCopyTask or null if end reached
     */
    @Override
    public FileCopyTask nextRecord(FileCopyTask reuse) throws IOException;
    
    /**
     * Close input format
     */
    @Override
    public void close() throws IOException;
}

// Create input format with tasks
List<FileCopyTask> copyTasks = getCopyTasks(sourcePath);
FileCopyTaskInputFormat inputFormat = new FileCopyTaskInputFormat(copyTasks);

// Use with DataSource
DataSet<FileCopyTask> inputTasks = new DataSource<>(
    env,
    inputFormat,
    new GenericTypeInfo<>(FileCopyTask.class),
    "fileCopyTasks"
);

// Process tasks with custom function
DataSet<Object> results = inputTasks.flatMap(new FileCopyProcessor());

// Create copy tasks from source directory
List<FileCopyTask> tasks = getCopyTasks(sourcePath);

// Create DataSource with custom input format
DataSet<FileCopyTask> inputTasks = new DataSource<>(
    env,
    new FileCopyTaskInputFormat(tasks),
    new GenericTypeInfo<>(FileCopyTask.class),
    "fileCopyTasks"
);

// Process each task with rich flat map function
FlatMapOperator<FileCopyTask, Object> results = inputTasks.flatMap(
    new RichFlatMapFunction<FileCopyTask, Object>() {
        private LongCounter fileCounter;
        private LongCounter bytesCounter;
        
        @Override
        public void open(Configuration parameters) throws Exception {
            bytesCounter = getRuntimeContext().getLongCounter(BYTES_COPIED_CNT_NAME);
            fileCounter = getRuntimeContext().getLongCounter(FILES_COPIED_CNT_NAME);
        }
        
        @Override
        public void flatMap(FileCopyTask task, Collector<Object> out) throws Exception {
            // Perform actual file copy operation
            copyFile(task);
        }
    }
);

private static List<FileCopyTask> getCopyTasks(Path sourcePath) throws IOException {
    List<FileCopyTask> tasks = new ArrayList<>();
    getCopyTasks(sourcePath, "", tasks);
    return tasks;
}

private static void getCopyTasks(Path p, String rel, List<FileCopyTask> tasks) throws IOException {
    FileStatus[] fileStatuses = p.getFileSystem().listStatus(p);
    if (fileStatuses == null) {
        return;
    }
    
    for (FileStatus fs : fileStatuses) {
        if (fs.isDir()) {
            // Recursively process directories
            getCopyTasks(fs.getPath(), rel + fs.getPath().getName() + "/", tasks);
        } else {
            // Add file to copy tasks
            Path filePath = fs.getPath();
            tasks.add(new FileCopyTask(filePath, rel + filePath.getName()));
        }
    }
}

// Check execution environment
private static boolean isLocal(final ExecutionEnvironment env) {
    return env instanceof LocalEnvironment;
}

// Check file system type
private static boolean isOnDistributedFS(final Path path) throws IOException {
    return path.getFileSystem().isDistributedFS();
}

// Validate paths for distributed execution
if (!isLocal(env) && !(isOnDistributedFS(sourcePath) && isOnDistributedFS(targetPath))) {
    System.out.println("In a distributed mode only HDFS input/output paths are supported");
    return;
}

// Initialize counters in open() method
private LongCounter fileCounter;
private LongCounter bytesCounter;

@Override
public void open(Configuration parameters) throws Exception {
    bytesCounter = getRuntimeContext().getLongCounter(BYTES_COPIED_CNT_NAME);
    fileCounter = getRuntimeContext().getLongCounter(FILES_COPIED_CNT_NAME);
}

// Update counters during copy operation
int bytes = IOUtils.copy(inputStream, outputStream);
bytesCounter.add(bytes);
fileCounter.add(1L);

// Access results after execution
Map<String, Object> accumulators = env.getLastJobExecutionResult().getAllAccumulatorResults();
System.out.println("Files copied: " + accumulators.get(FILES_COPIED_CNT_NAME));
System.out.println("Bytes copied: " + accumulators.get(BYTES_COPIED_CNT_NAME));

// Required parameters
--input <path>      // Source directory or file path
--output <path>     // Destination directory path

// Optional parameters  
--parallelism <n>   // Number of parallel workers (default: 10)

// Flink file system types
import org.apache.flink.core.fs.Path;
import org.apache.flink.core.fs.FileSystem;
import org.apache.flink.core.fs.FileStatus;
import org.apache.flink.core.fs.FSDataInputStream;
import org.apache.flink.core.fs.FSDataOutputStream;

// File copy task
FileCopyTask task = new FileCopyTask(sourcePath, relativePath);

// Input format and splits
FileCopyTaskInputFormat inputFormat = new FileCopyTaskInputFormat(tasks);
FileCopyTaskInputSplit split = new FileCopyTaskInputSplit(task, splitNumber);

// Accumulator types for metrics
LongCounter bytesCounter;
LongCounter filesCounter;