Performing a Resumable Download

API Description

This API is an encapsulated and enhanced version of multipart download, and aims to eliminate large file download failures caused by poor network conditions and program breakdowns.

Method Definition

ObsClient.downloadFile

Request Parameter

Returned Result (InterfaceResult)

Sample Code

This example downloads objectname from examplebucket in a resumable download and prints the progress.

// Use npm to install the client.
var ObsClient = require('esdk-obs-nodejs');

// Obtain an AK/SK pair using environment variables or import the AK/SK pair in other ways. Using hard coding may result in leakage.
// Obtain an AK/SK pair on the management console by referring to https://support.huaweicloud.com/intl/en-us/usermanual-ca/ca_01_0003.html.
const AK = process.env.AccessKeyID
const SK = process.env.SecretAccessKey
// (Optional) If you use a temporary AK/SK pair and a security token to access OBS, obtain them using environment variables.
const security_token= process.env.SecurityToken
// Set server to the endpoint corresponding to the bucket. CN-Hong Kong is used here as an example. Replace it with the one in your actual situation.
const server = "https://obs.ap-southeast-1.myhuaweicloud.com"

var obsClient = new ObsClient({
    access_key_id: AK,
    secret_access_key: SK,
    server: server,
});
const Bucket = 'examplebucket'
// Name of the object to be downloaded
const Key = 'objectname'
// Set the local path the object will be downloaded to.
const DownloadFile = 'D:\\example'
// Set the part size to 10 MB.
const PartSize = 10 * 1024 * 1024
// Number of concurrent downloads
const TaskNum = 10
// Define the control parameter used for canceling the resumable download.
var hook;
// Perform the resumable download.
try {
    obsClient.downloadFile({
        Bucket,
        Key,
        DownloadFile,
        PartSize,
        TaskNum,
        // Enable the resumable download.
        EnableCheckpoint: true,
        // Progress callback
        ProgressCallback: function (transferredAmount, totalAmount, totalSeconds) {
            // Print the download speed in KB/s.
            console.log(transferredAmount * 1.0 / totalSeconds / 1024);
            // Print the download percentage.
            console.log(transferredAmount * 100.0 / totalAmount);
            // Pause the download when the progress reaches 50%.
            // if(hook && (transferredAmount / totalAmount) > 0.5){
            //     // Pause the resumable download.
            //     hook.cancel();
            // }
        },
        ResumeCallback : function(resumeHook){
            // Obtain the control parameter used for canceling the resumable download.
            hook = resumeHook;
        }
    }, (err, result) => {
        if (err) {
            console.log('DownloadFile Failed')
            console.error('Error-->' + err);
        } else {
            if (result.CommonMsg.Status < 300) {
                console.log('DownloadFile Succeeded')
                console.log('RequestId-->' + result.InterfaceResult.RequestId);
                console.log('LastModified-->' + result.InterfaceResult.LastModified);
                console.log('Metadata-->' + JSON.stringify(result.InterfaceResult.Metadata)); 
            } else {
                console.log('DownloadFile Failed')
                console.log('ErrorCode-->' + result.CommonMsg.Code);
                console.log('ErrorMessage-->' + result.CommonMsg.Message);
            }
        }
    });
} catch (error) {
    console.log('DownloadFile Failed')
    console.error('Error-->' + error);
}