Google App Engine 中 blobstore 对象的 1MB 配额限制？

Question

我正在使用 App Engine（版本 1.4.3）直接编写blobstore 以保存图像。 当我尝试存储大于 1MB 的图像时，出现以下异常

com.google.apphosting.api.ApiProxy$RequestTooLargeException: The request to API call datastore_v3.Put() was too large.

我认为 每个对象的限制是2GB

这是存储图像的Java代码

private void putInBlobStore(final String mimeType, final byte[] data) throws IOException {
    final FileService fileService = FileServiceFactory.getFileService();
    final AppEngineFile file = fileService.createNewBlobFile(mimeType);
    final FileWriteChannel writeChannel = fileService.openWriteChannel(file, true);
    writeChannel.write(ByteBuffer.wrap(data));
    writeChannel.closeFinally();
}

Answer 1

以下是我读取和写入大文件的方法：

public byte[] readImageData(BlobKey blobKey, long blobSize) {
    BlobstoreService blobStoreService = BlobstoreServiceFactory
            .getBlobstoreService();
    byte[] allTheBytes = new byte[0];
    long amountLeftToRead = blobSize;
    long startIndex = 0;
    while (amountLeftToRead > 0) {
        long amountToReadNow = Math.min(
                BlobstoreService.MAX_BLOB_FETCH_SIZE - 1, amountLeftToRead);

        byte[] chunkOfBytes = blobStoreService.fetchData(blobKey,
                startIndex, startIndex + amountToReadNow - 1);

        allTheBytes = ArrayUtils.addAll(allTheBytes, chunkOfBytes);

        amountLeftToRead -= amountToReadNow;
        startIndex += amountToReadNow;
    }

    return allTheBytes;
}

public BlobKey writeImageData(byte[] bytes) throws IOException {
    FileService fileService = FileServiceFactory.getFileService();

    AppEngineFile file = fileService.createNewBlobFile("image/jpeg");
    boolean lock = true;
    FileWriteChannel writeChannel = fileService
            .openWriteChannel(file, lock);

    writeChannel.write(ByteBuffer.wrap(bytes));
    writeChannel.closeFinally();

    return fileService.getBlobKey(file);
}

Answer 2

最大对象大小为 2 GB，但每个 API 调用最多只能处理 1 MB。至少对于阅读来说是这样，但我认为对于写作来说可能也是如此。因此，您可以尝试将对象的写入拆分为 1 MB 的块，看看是否有帮助。

Answer 3

正如布鲁莫上面所建议的，如果你把它分成块< 1MB就可以了。这是一些代码。

public BlobKey putInBlobStoreString(String fileName, String contentType, byte[] filebytes) throws IOException {
    // Get a file service
    FileService fileService = FileServiceFactory.getFileService();
    AppEngineFile file = fileService.createNewBlobFile(contentType, fileName);
    // Open a channel to write to it
    boolean lock = true;
    FileWriteChannel writeChannel = null;
    writeChannel = fileService.openWriteChannel(file, lock);
    // lets buffer the bitch
    BufferedInputStream in = new BufferedInputStream(new ByteArrayInputStream(filebytes));
    byte[] buffer = new byte[524288]; // 0.5 MB buffers
    int read;
    while( (read = in.read(buffer)) > 0 ){ //-1 means EndOfStream
        ByteBuffer bb = ByteBuffer.wrap(buffer);
        writeChannel.write(bb);
    }
    writeChannel.closeFinally();
    return fileService.getBlobKey(file);
}