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Descargar un archivo en fragmentos simultáneamente

Usa Gestor de transferencias para descargar un archivo grande en fragmentos, con simultaneidad.

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Para obtener documentación detallada que incluya este código de muestra, consulta lo siguiente:

Descargas de objetos segmentados

Código de ejemplo

Go

Para obtener más información, consulta la documentación de referencia de la API Go de Cloud Storage.

Para autenticarte en Cloud Storage, configura las credenciales predeterminadas de la aplicación. Para obtener más información, consulta el artículo Configurar la autenticación para bibliotecas de cliente.

package transfermanager

import (
	"context"
	"fmt"
	"io"
	"os"

	"cloud.google.com/go/storage"
	"cloud.google.com/go/storage/transfermanager"
)

// downloadChunksConcurrently downloads a single file in chunks, concurrently in a process pool.
func downloadChunksConcurrently(w io.Writer, bucketName, blobName, filename string) error {
	// bucketName := "your-bucket-name"
	// blobName := "target-file"
	// filename := "path/to/your/local/file.txt"

	// The chunkSize is the size of each chunk to be downloaded.
	// The performance impact of this value depends on the use case.
	// For example, for a slow network, using a smaller chunkSize may be better.
	// Providing this parameter is optional and the default value is 32 MiB.
	chunkSize := 16 * 1024 * 1024 // 16 MiB

	// The maximum number of workers to use for the operation.
	// Please note, providing this parameter is optional.
	// The performance impact of this value depends on the use case.
	// To download one large file, the default value: NumCPU / 2 is usually fine.
	workers := 8

	ctx := context.Background()
	client, err := storage.NewClient(ctx)
	if err != nil {
		return fmt.Errorf("storage.NewClient: %w", err)
	}
	defer client.Close()

	d, err := transfermanager.NewDownloader(client, transfermanager.WithPartSize(int64(chunkSize)), transfermanager.WithWorkers(workers))
	if err != nil {
		return fmt.Errorf("transfermanager.NewDownloader: %w", err)
	}

	f, err := os.Create(filename)
	if err != nil {
		return fmt.Errorf("os.Create: %w", err)
	}
	defer f.Close()

	in := &transfermanager.DownloadObjectInput{
		Bucket:      bucketName,
		Object:      blobName,
		Destination: f,
	}

	if err := d.DownloadObject(ctx, in); err != nil {
		return fmt.Errorf("d.DownloadObject: %w", err)
	}

	// Wait for all downloads to complete and close the downloader.
	// This allows to synchronize the download processes.
	results, err := d.WaitAndClose()
	if err != nil {
		return fmt.Errorf("d.WaitAndClose: %w", err)
	}

	// Process the downloader result.
	if len(results) != 1 {
		return fmt.Errorf("expected 1 result, got %d", len(results))
	}
	result := results[0]
	if result.Err != nil {
		fmt.Fprintf(w, "download of %v failed with error %v\n", result.Object, result.Err)
		return result.Err
	}
	fmt.Fprintf(w, "Downloaded %v to %v.\n", blobName, filename)

	return nil
}

Java

Para obtener más información, consulta la documentación de referencia de la API Java de Cloud Storage.

import com.google.cloud.storage.BlobInfo;
import com.google.cloud.storage.transfermanager.DownloadResult;
import com.google.cloud.storage.transfermanager.ParallelDownloadConfig;
import com.google.cloud.storage.transfermanager.TransferManager;
import com.google.cloud.storage.transfermanager.TransferManagerConfig;
import java.nio.file.Path;
import java.util.List;

class AllowDivideAndConquerDownload {

  public static void divideAndConquerDownloadAllowed(
      List<BlobInfo> blobs, String bucketName, Path destinationDirectory) {
    TransferManager transferManager =
        TransferManagerConfig.newBuilder()
            .setAllowDivideAndConquerDownload(true)
            .build()
            .getService();
    ParallelDownloadConfig parallelDownloadConfig =
        ParallelDownloadConfig.newBuilder()
            .setBucketName(bucketName)
            .setDownloadDirectory(destinationDirectory)
            .build();
    List<DownloadResult> results =
        transferManager.downloadBlobs(blobs, parallelDownloadConfig).getDownloadResults();

    for (DownloadResult result : results) {
      System.out.println(
          "Download of "
              + result.getInput().getName()
              + " completed with status "
              + result.getStatus());
    }
  }
}

Node.js

Para obtener más información, consulta la documentación de referencia de la API Node.js de Cloud Storage.

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// The ID of your GCS bucket
// const bucketName = 'your-unique-bucket-name';

// The ID of the GCS file to download
// const fileName = 'your-file-name';

// The path to which the file should be downloaded
// const destFileName = '/local/path/to/file.txt';

// The size of each chunk to be downloaded
// const chunkSize = 1024;

// Imports the Google Cloud client library
const {Storage, TransferManager} = require('@google-cloud/storage');

// Creates a client
const storage = new Storage();

// Creates a transfer manager client
const transferManager = new TransferManager(storage.bucket(bucketName));

async function downloadFileInChunksWithTransferManager() {
  // Downloads the files
  await transferManager.downloadFileInChunks(fileName, {
    destination: destFileName,
    chunkSizeBytes: chunkSize,
  });

  console.log(
    `gs://${bucketName}/${fileName} downloaded to ${destFileName}.`
  );
}

downloadFileInChunksWithTransferManager().catch(console.error);

Python

Para obtener más información, consulta la documentación de referencia de la API Python de Cloud Storage.

def download_chunks_concurrently(
    bucket_name, blob_name, filename, chunk_size=32 * 1024 * 1024, workers=8
):
    """Download a single file in chunks, concurrently in a process pool."""

    # The ID of your GCS bucket
    # bucket_name = "your-bucket-name"

    # The file to be downloaded
    # blob_name = "target-file"

    # The destination filename or path
    # filename = ""

    # The size of each chunk. The performance impact of this value depends on
    # the use case. The remote service has a minimum of 5 MiB and a maximum of
    # 5 GiB.
    # chunk_size = 32 * 1024 * 1024 (32 MiB)

    # The maximum number of processes to use for the operation. The performance
    # impact of this value depends on the use case, but smaller files usually
    # benefit from a higher number of processes. Each additional process occupies
    # some CPU and memory resources until finished. Threads can be used instead
    # of processes by passing `worker_type=transfer_manager.THREAD`.
    # workers=8

    from google.cloud.storage import Client, transfer_manager

    storage_client = Client()
    bucket = storage_client.bucket(bucket_name)
    blob = bucket.blob(blob_name)

    transfer_manager.download_chunks_concurrently(
        blob, filename, chunk_size=chunk_size, max_workers=workers
    )

    print("Downloaded {} to {}.".format(blob_name, filename))

Siguientes pasos

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