• Object Storage Service

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  4. Operations on Objects
  5. Complete Multipart Upload

Complete Multipart Upload

After uploading all parts for a multipart upload, you can use this operation to complete the multipart upload.

Upon receiving a Complete Multipart Upload request, OBS concatenates the specified parts to create a new object. All associated parts cannot be downloaded until the multipart upload is complete.

When starting to complete a multipart upload, OBS first copies the header information from the metadata of associated parts and then incorporates the header information into the metadata of the newly created object.

Before a multipart upload is completed, all associated parts occupy storage quota. After the multipart upload is completed, only parts included in the part list specified in the Complete Multipart Upload request are concatenated. These parts still occupy storage quota while other parts are deleted to release storage quota.

After a multipart upload is completed, you can send a GET request to obtain the newly created object or some parts comprising this object by specifying a range in the request. You can also send a DELETE request to delete all parts uploaded for the multipart upload. The deleted parts cannot be restored.

The MD5 value recorded in the ETag of a newly created object is calculated using the MD5 values of the parts comprising this object. The object ETag is calculated as follows:



Mn is the MD5 value of part N

N is the total number of parts


If a bucket has versioning enabled, a unique version ID is generated for an object created from a multipart upload in this bucket and the version ID is returned in response header x-amz-version-id. If the bucket has versioning suspended, the version ID of the object is null. For details about bucket versioning, see section PUT Bucket versioning.

If 10 parts are uploaded but only 9 parts are selected for combination, the part that is not combined will be automatically deleted. After the part is deleted, it cannot be restored. Before combining the parts, adopt the interface used to list the parts that have been uploaded to check all parts to ensure that no part is missed.