FileSystem Factory

/**
 * A file system factory for Hadoop-based file systems.
 * Calls Hadoop's mechanism to find a file system implementation for a given file
 * system scheme and wraps it as a Flink file system.
 */
public class HadoopFsFactory implements FileSystemFactory {
    public HadoopFsFactory();
    
    /**
     * Returns the scheme handled by this factory.
     * @return "*" indicating it handles various schemes
     */
    public String getScheme();
    
    /**
     * Configures the factory with Flink configuration.
     * @param config Flink's configuration object
     */
    public void configure(Configuration config);
    
    /**
     * Creates a file system instance for the given URI.
     * @param fsUri URI of the file system to create
     * @return FileSystem instance wrapped as Flink FileSystem
     * @throws IOException if file system creation fails
     * @throws UnsupportedFileSystemSchemeException if scheme is not supported
     */
    public FileSystem create(URI fsUri) throws IOException;
}

import org.apache.flink.runtime.fs.hdfs.HadoopFsFactory;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.core.fs.FileSystem;
import java.net.URI;

// Create and configure factory
HadoopFsFactory factory = new HadoopFsFactory();
Configuration config = new Configuration();
// Add Hadoop configuration properties to Flink config if needed
config.setString("fs.defaultFS", "hdfs://namenode:9000");
factory.configure(config);

// Create HDFS file system
URI hdfsUri = URI.create("hdfs://namenode:9000/");
FileSystem hdfsFs = factory.create(hdfsUri);

// Create S3 file system
URI s3Uri = URI.create("s3a://my-bucket/");
FileSystem s3Fs = factory.create(s3Uri);

// Create local file system
URI localUri = URI.create("file:///tmp/");
FileSystem localFs = factory.create(localUri);

import org.apache.flink.configuration.Configuration;

Configuration config = new Configuration();

// Set Hadoop configuration through Flink config
config.setString("fs.defaultFS", "hdfs://namenode:9000");
config.setString("fs.hdfs.impl", "org.apache.hadoop.hdfs.DistributedFileSystem");
config.setString("fs.s3a.access.key", "your-access-key");
config.setString("fs.s3a.secret.key", "your-secret-key");

// Configure connection limits
config.setInteger("fs.hdfs.limit.total", 100);
config.setInteger("fs.hdfs.limit.input", 50);
config.setInteger("fs.hdfs.limit.output", 50);
config.setLong("fs.hdfs.limit.timeout", 30000L);

factory.configure(config);

// HDFS schemes
FileSystem hdfs1 = factory.create(URI.create("hdfs://namenode:9000/"));
FileSystem hdfs2 = factory.create(URI.create("hdfs://ha-cluster/"));

// S3 schemes
FileSystem s3a = factory.create(URI.create("s3a://bucket/"));
FileSystem s3n = factory.create(URI.create("s3n://bucket/"));
FileSystem s3 = factory.create(URI.create("s3://bucket/"));

// Azure schemes
FileSystem wasb = factory.create(URI.create("wasb://container@account.blob.core.windows.net/"));
FileSystem abfs = factory.create(URI.create("abfs://container@account.dfs.core.windows.net/"));

// Google Cloud Storage
FileSystem gcs = factory.create(URI.create("gs://bucket/"));

// Local file system
FileSystem local = factory.create(URI.create("file:///path/"));

Configuration config = new Configuration();

// Set total connection limit for HDFS
config.setInteger("fs.hdfs.limit.total", 100);

// Set input stream connection limit
config.setInteger("fs.hdfs.limit.input", 50);

// Set output stream connection limit  
config.setInteger("fs.hdfs.limit.output", 30);

// Set connection timeout (milliseconds)
config.setLong("fs.hdfs.limit.timeout", 30000L);

// Set stream inactivity timeout (milliseconds)
config.setLong("fs.hdfs.limit.stream-timeout", 300000L);

factory.configure(config);

// Created file system will automatically use connection limiting
FileSystem limitedFs = factory.create(URI.create("hdfs://namenode:9000/"));

try {
    FileSystem fs = factory.create(URI.create("hdfs://invalid-host:9000/"));
} catch (UnsupportedFileSystemSchemeException e) {
    // Scheme not supported or Hadoop classes missing
    System.err.println("Unsupported scheme: " + e.getMessage());
} catch (UnknownHostException e) {
    // Authority cannot be resolved
    System.err.println("Cannot resolve host: " + e.getMessage());
} catch (IOException e) {
    // General I/O error during file system creation
    System.err.println("File system creation failed: " + e.getMessage());
}

Configuration config = new Configuration();
config.setString("fs.defaultFS", "hdfs://namenode:9000");
factory.configure(config);

// This URI has no authority
URI uriNoAuthority = URI.create("hdfs:///path/to/file");

// Factory will use fs.defaultFS to resolve authority
FileSystem fs = factory.create(uriNoAuthority);
// Results in: hdfs://namenode:9000/path/to/file

// Flink's FileSystemFactory interface
public interface FileSystemFactory {
    String getScheme();
    void configure(Configuration config);
    FileSystem create(URI fsUri) throws IOException;
}

// Flink's Configuration class
public class Configuration {
    public void setString(String key, String value);
    public void setInteger(String key, int value);
    public void setLong(String key, long value);
    public String getString(String key, String defaultValue);
}

// Exceptions thrown by factory
public class UnsupportedFileSystemSchemeException extends IOException {
    public UnsupportedFileSystemSchemeException(String message, Throwable cause);
}