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Multipart Upload Overview

To upload a large file, multipart upload is recommended. Multipart upload is applicable to many scenarios, when:

  • files to be uploaded are larger than 100 MB.
  • the network condition is poor. Connection to the OBS server is constantly down.
  • sizes of files to be uploaded are uncertain.

Multipart upload consists of three steps:

  1. Initialize a multipart upload (ObsClient.InitiateMultipartUpload).
  2. Upload parts one by one or concurrently (ObsClient.UploadPart).
  3. Combine parts (ObsClient.CompleteMultipartUpload) or abort the multipart upload (ObsClient.AbortMultipartUpload).

The following code shows how to perform multipart upload:

import (
       "fmt"
       "obs"
)

var ak = "*** Provide your Access Key ***"
var sk = "*** Provide your Secret Key ***"
var endpoint = "https://your-endpoint"

// Create an ObsClient struct.
var obsClient, _ = obs.New(ak, sk, endpoint)

func main() {
       var uploadId = ""
       var eTag1 = ""
       var eTag2 = ""

       // Initialize a multipart upload.
       inputInit := &obs.InitiateMultipartUploadInput{}
       inputInit.Bucket = "bucketname"
       inputInit.Key = "objectkey"
       outputInit, err := obsClient.InitiateMultipartUpload(inputInit)
       if err == nil {
              fmt.Printf("RequestId:%s\n", outputInit.RequestId)
              fmt.Printf("UploadId:%s\n", outputInit.UploadId)
              uploadId = outputInit.UploadId
       } else {
              if obsError, ok := err.(obs.ObsError); ok {
                     fmt.Println(obsError.Code)
                     fmt.Println(obsError.Message)
              } else {
                     fmt.Println(err)
              }
       }

       // Upload a part.
       inputUploadPart := &obs.UploadPartInput{}
       inputUploadPart.Bucket = "bucketname"
       inputUploadPart.Key = "objectkey"
       inputUploadPart.UploadId = uploadId
       inputUploadPart.PartNumber = "partNumber1"
       inputUploadPart.SourceFile = "localFilePath"
       outputUploadPart, err := obsClient.UploadPart(inputUploadPart)
       if err == nil {
              fmt.Printf("RequestId:%s\n", outputUploadPart.RequestId)
              fmt.Printf("ETag:%s\n", outputUploadPart.ETag)
              eTag1 = outputUploadPart.ETag
       } else {
              if obsError, ok := err.(obs.ObsError); ok {
                     fmt.Println(obsError.Code)
                     fmt.Println(obsError.Message)
              } else {
                     fmt.Println(err)
              }
       }
       inputUploadPart = &obs.UploadPartInput{}
       inputUploadPart.Bucket = "bucketname"
       inputUploadPart.Key = "objectkey"
       inputUploadPart.UploadId = uploadId
       inputUploadPart.PartNumber = "partNumber2"
       inputUploadPart.SourceFile = "localFilePath"
       outputUploadPart, err = obsClient.UploadPart(inputUploadPart)
       if err == nil {
              fmt.Printf("RequestId:%s\n", outputUploadPart.RequestId)
              fmt.Printf("ETag:%s\n", outputUploadPart.ETag)
              eTag2 = outputUploadPart.ETag
       } else {
              if obsError, ok := err.(obs.ObsError); ok {
                     fmt.Println(obsError.Code)
                     fmt.Println(obsError.Message)
              } else {
                     fmt.Println(err)
              }
       }

       // Combine parts.
       inputCompleteMultipart := &obs.CompleteMultipartUploadInput{}
       inputCompleteMultipart.Bucket = "bucketname"
       inputCompleteMultipart.Key = "objectkey"
       inputCompleteMultipart.UploadId = uploadId
       inputCompleteMultipart.Parts = []obs.Part{
              obs.Part{PartNumber: "partNumber1", ETag: eTag1},
              obs.Part{PartNumber: "partNumber2", ETag: eTag2},
       }
       outputCompleteMultipart, err := obsClient.CompleteMultipartUpload(inputCompleteMultipart)
       if err == nil {
              fmt.Printf("RequestId:%s\n", outputCompleteMultipart.RequestId)
              fmt.Printf("Location:%s, Bucket:%s, Key:%s, ETag:%s\n", outputCompleteMultipart.Location, outputCompleteMultipart.Bucket, outputCompleteMultipart.Key, outputCompleteMultipart.ETag)
       } else {
              if obsError, ok := err.(obs.ObsError); ok {
                     fmt.Println(obsError.Code)
                     fmt.Println(obsError.Message)
              } else {
                     fmt.Println(err)
              }
       }
}

For details about other operations of multipart upload, see: