API operation for initiating a multipart upload - Object Storage Service

Initiates a multipart upload task before you can upload data in parts to Object Storage Service (OSS).

Usage notes

When you call the InitiateMultipartUpload operation, OSS creates and returns a unique upload ID to identify the multipart upload task. You can initiate operations such as stopping or querying the multipart upload task by using this upload ID.
When you initiate a multipart upload request to upload an object, the existing object that has the same name is not affected.
The InitiateMultipartUpload operation requires ?uploads to be present in CanonicalizedResource to implement the authentication signature calculation.
To call the InitiateMultipartUpload operation, you must have the oss:PutObject permission. For more information, see Common examples of RAM policies.

Request syntax

POST /ObjectName?uploads HTTP/1.1
Host: BucketName.oss-cn-hangzhou.aliyuncs.com
Date: GMT date
Authorization: SignatureValue

Request headers

InitiateMultipartUpload requests support custom headers that start with x-oss-meta- and the following standard HTTP request headers: Cache-Control, Content-Disposition, Content-Encoding, Content-Type, and Expires. For more information, see PutObject.

Header	Type	Description
Cache-Control	String	The caching behavior of the web page when the object is downloaded. For more information, see RFC 2616. This header is empty by default.
Content-Disposition	String	The name of the object when the object is downloaded. For more information, see RFC 2616. This header is empty by default.
Content-Encoding	String	The content encoding format of the object when the object is downloaded. For more information, see RFC 2616. This header is empty by default.
Expires	Integer	The expiration time of the cache. Unit: milliseconds. For more information, see RFC 2616. This header is empty by default.
x-oss-forbid-overwrite	String	Specifies whether the InitiateMultipartUpload operation overwrites the existing object that has the same name as the object that you want to upload. If versioning is enabled or suspended for the bucket to which you want to upload the object, the x-oss-forbid-overwrite header does not take effect. As a result, the object that is uploaded by calling the InitiateMultipartUpload operation overwrites the existing object that has the same name. If you do not specify the x-oss-forbid-overwrite header or you set the x-oss-forbid-overwrite header to false, the operation overwrites an existing object that has the same name. If you set the x-oss-forbid-overwrite header to true, an existing object that has the same name cannot be overwritten. If you specify the x-oss-forbid-overwrite header, the queries per second (QPS) performance of OSS may be degraded. If you want to specify the x-oss-forbid-overwrite header in a large number of requests (QPS greater than 1,000), contact technical support.
x-oss-server-side-encryption	String	The server-side encryption method that is used to encrypt each part of the object that you want to upload. Valid values: AES256 and KMS Important To use the KMS encryption method, make sure that Key Management Service (KMS) is activated. If you specify this header in the request, this header is included in the response. OSS uses the method specified by this header to encrypt each uploaded part. When you download the object, the x-oss-server-side-encryption header is included in the response and the header value is set to the method that is used to encrypt the object.
x-oss-server-side-encryption-key-id	String	The ID of the customer master key (CMK) managed by KMS. This parameter is valid only when x-oss-server-side-encryption is set to KMS.
x-oss-storage-class	String	The storage class of the object that you want to upload. If you specify the storage class when you upload the object, the specified storage class applies regardless of the storage class of the bucket to which the object is uploaded. For example, if you set x-oss-storage-class to Standard when you upload an object to an Infrequent Access (IA) bucket, the storage class of the uploaded object is Standard. Valid values: Standard IA Archive ColdArchive For more information about the storage classes, see Overview.
x-oss-tagging	String	The tag of the object. You can configure multiple tags for the object. Example: TagA=A&TagB=B. Note The tag key and value must be URL-encoded. If a tag does not contain an equal sign (`=`), the tag value is considered an empty string.

Request parameters

When you call the InitiateMultipartUpload operation, you can specify the encoding-type parameter in the request to encode the object name returned in the response.

Parameter

Type

Description

encoding-type

String

The method used to encode the object name in the response. Only URL encoding is supported. The object name can contain characters that are encoded in UTF-8. However, the XML 1.0 standard cannot be used to parse some control characters, such as characters with an ASCII value from 0 to 10. If an object name contains control characters that are not supported by XML 1.0, the solution is to configure the encoding-type parameter to encode the object names in the response.

This header is empty by default.

Valid value: url

Response parameters

After OSS receives an InitiateMultipartUpload request, OSS returns a response that contains a message body in the XML format. The message body contains the following parameters: Bucket, Key, and UploadID.

Parameter	Type	Description
InitiateMultipartUploadResult	Container	The container that stores the results of the InitiateMultipartUpload request. Child nodes: Bucket, Key, UploadId, and EncodingType Parent nodes: none
Bucket	String	The name of the bucket to which the object is uploaded by the multipart upload task. Parent nodes: InitiateMultipartUploadResult
Key	String	The name of the object that is uploaded by the multipart upload task. Parent nodes: InitiateMultipartUploadResult
UploadId	String	The upload ID that uniquely identifies the multipart upload task. The upload ID is used to call UploadPart and CompleteMultipartUpload later. Parent nodes: InitiateMultipartUploadResult
EncodingType	String	The encoding type of the object name in the response. If the encoding-type parameter is specified in the request, the object name in the response is encoded. Parent nodes: InitiateMultipartUploadResult

The response headers involved in this API operation include common response headers. For more information, see Common HTTP headers.

Description

Sample requests

POST /multipart.data?uploads HTTP/1.1 
Host: oss-example.oss-cn-hangzhou.aliyuncs.com 
Date: Wed, 22 Feb 2012 08:32:21 GMT 
x-oss-storage-class: Archive
Authorization: OSS qn6q**************:77Dv****************

Sample success responses

HTTP/1.1 200 OK
Content-Length: 230
Server: AliyunOSS
Connection: keep-alive
x-oss-request-id: 42c25703-7503-fbd8-670a-bda01eae****
Date: Wed, 22 Feb 2012 08:32:21 GMT
Content-Type: application/xml
<?xml version="1.0" encoding="UTF-8"?>
<InitiateMultipartUploadResult xmlns="http://doc.oss-cn-hangzhou.aliyuncs.com">
    <Bucket>oss-example</Bucket>
    <Key>multipart.data</Key>
    <UploadId>0004B9894A22E5B1888A1E29F823****</UploadId>
</InitiateMultipartUploadResult>

SDK

You can use OSS SDKs for the following programming languages to call the InitiateMultipartUpload operation:

Error codes

Error code	HTTP status code	Description
InvalidEncryptionAlgorithmError	400	A server-side encryption method other than AES 256 and KMS is specified.
InvalidArgument	400	The x-oss-server-side-encryption header is specified each time a part is uploaded.
InvalidArgument	400	The specified storage class of the object to upload is invalid.
KmsServiceNotEnabled	403	KMS is specified as the server-side encryption method but KMS is not activated.
FileAlreadyExists	409	The request contains the `x-oss-forbid-overwrite=true` header, and the bucket contains an object that has the same name as the object that you want to upload. The object that you want to upload by using InitiateMultipartUpload is a directory in a bucket for which the hierarchical namespace feature is enabled.