Performing a Resumable Upload

Uploading large files often fails due to poor network conditions or program breakdowns. It is a waste of resources to restart the upload process upon an upload failure, and the restarted upload process may still suffer from the unstable network. To resolve such issues, you can use the API for resumable upload, whose working principle is to divide the to-be-uploaded file into multiple parts and upload them separately. The upload result of each part is recorded in a checkpoint file in real time. Only when all parts are successfully uploaded, the result indicating a successful upload is returned. Otherwise, an exception is thrown to remind you of calling the API again for re-uploading. Based on the upload status of each part recorded in the checkpoint file, the re-uploading will upload the parts failed to be uploaded previously, instead of uploading all parts. By virtue of this, resources are saved and efficiency is improved.

You can call ObsClient.UploadFile to perform a resumable upload. The following table describes the parameters involved in this API.

Sample code:

// Initialize configuration parameters.
ObsConfig config = new ObsConfig();
config.Endpoint = "https://your-endpoint";
// Hard-coded or plaintext AK/SK are risky. For security purposes, encrypt your AK/SK and store them in the configuration file or environment variables. In this example, the AK/SK are stored in environment variables for identity authentication. Before running this example, configure environment variables AccessKeyID and SecretAccessKey.
// Obtain an AK/SK pair on the management console. For details, see https://support.huaweicloud.com/eu/usermanual-ca/ca_01_0003.html.
string accessKey= Environment.GetEnvironmentVariable("AccessKeyID", EnvironmentVariableTarget.Machine);
string secretKey= Environment.GetEnvironmentVariable("SecretAccessKey", EnvironmentVariableTarget.Machine);
// Create an instance of ObsClient.
ObsClient client = new ObsClient(accessKey, secretKey, config);
// Perform a resumable upload.
try
{
    UploadFileRequest request = new UploadFileRequest
    {
        BucketName = "bucketname",
        ObjectKey = "objectname",
        // Specify the local file to be uploaded.
        UploadFile = "localpath",
        // Set the part size to 10 MB.
        UploadPartSize = 10 * 1024 * 1024,
        // Enable the resumable download mode.
        EnableCheckpoint = true,
    };
    // Represent the progress by showing how many bytes have been uploaded.
    request.ProgressType = ProgressTypeEnum.ByBytes;
    // Refresh the upload progress each time 1 MB data is uploaded.
    request.ProgressInterval = 1024 * 1024;

    // Register the upload progress callback function. 
    request.UploadProgress += delegate(object sender, TransferStatus status){
        // Obtain the average upload rate.
        Console.WriteLine("AverageSpeed: {0}", status.AverageSpeed / 1024  + "KB/S");
        // Obtain the upload progress in percentage.
        Console.WriteLine("TransferPercentage: {0}", status.TransferPercentage);
    };
    
    // Register the upload event callback function. 
    request.UploadEventHandler += delegate(object sender, ResumableUploadEvent e){       
        // Obtain the upload events.
        Console.WriteLine("EventType: {0}", e.EventType);
    };
     
    CompleteMultipartUploadResponse response = client.UploadFile(request);
    Console.WriteLine("Upload File response: {0}", response.StatusCode);
}
catch (ObsException ex)
{
   Console.WriteLine("ErrorCode: {0}", ex.ErrorCode);
   Console.WriteLine("ErrorMessage: {0}", ex.ErrorMessage);
}

• The API for resumable upload, which is implemented based on multipart upload, is an encapsulated and enhanced version of multipart upload.
• This API saves resources and improves efficiency upon the re-upload, and speeds up the upload process by concurrently uploading parts. Because this API is transparent to users, users are free from concerns about internal service details, such as the creation and deletion of checkpoint files, division of objects, and concurrent upload of parts.

• The default value of the EnableCheckpoint parameter is false, which indicates that the resumable upload mode is disabled. In such cases, the API for resumable upload degrades to the simple encapsulation of multipart upload, and no checkpoint file will be generated.
• The CheckpointFile and EnableCheckSum parameters are valid only when EnableCheckpoint is true.