# Multipart Upload

#### Functions

After initiating a multipart upload, you can use this operation to upload parts for the multipart upload using its task ID. When parts are uploaded in a multipart upload of an object, the upload sequence does not affect part merging, namely, multiple parts can be uploaded concurrently.

Part sizes range from 100 KB to 5 GB. However, when parts are being merged, the size of the last uploaded part ranges from 0 to 5 GB. The upload part ID ranges from 1 to 10,000.

This operation supports server-side encryption.

The value of partNumber in a multipart task is unique. If you upload a part of the same partNumber repeatedly, the last part uploaded will overwrite the previous one. When multiple concurrent uploading of the same partNumber part of the same object is performed, the Last Write Win policy is applied. The time of Last Write is defined as the time when the metadata of the part is created. To ensure data accuracy, the client must be locked to ensure concurrent upload of the same part of the same object. Concurrent upload of different parts of the same object does not need to be locked.

#### Request Syntax

    PUT /ObjectName?partNumber=partNum&uploadId=uploadID  HTTP/1.1
    Host: bucketname.obs.region.example.com
    Date: date
    Content-Length: length
    Authorization: authorization
    Content-MD5:md5
    <object Content>

#### Request Parameters

This request uses parameters to specify the upload task ID and part number. Table 1 describes the parameters.

Table 1 Request parameters
Parameter | Description | Mandatory
--- | --- | ---
partNumber | Indicates the ID of a part to be uploaded. The value is an integer from 1 to 10000. Type: integer | Yes
uploadId | Indicates a multipart upload ID. Type: string | Yes

#### Request Headers

This request uses common headers. For details, see Table 3.

Table 2 Server encryption request headers
Header | Description | Mandatory
--- | --- | ---

x-obs-server-side-encryption-customer-algorithm

Indicates an encryption algorithm. The header is used in SSE-C mode.

Type: string

Example: x-obs-server-side-encryption-customer-algorithm:AES256

Constraint: This header must be used together with x-obs-server-side-encryption-customer-key and x-obs-server-side-encryption-customer-key-MD5.

No. This header is required when SSE-C is used. The encryption algorithm must be the same as that used to initiate multipart upload tasks.

x-obs-server-side-encryption-customer-key

Indicates a key used to encrypt objects. The header is used in SSE-C mode. This key is used to encrypt objects.

Type: string

Example: x-obs-server-side-encryption-customer-key:K7QkYpBkM5+hca27fsNkUnNVaobncnLht/rCB2o/9Cw=

Constraint: This header is a Base64-encoded 256-bit key and must be used together with x-obs-server-side-encryption-customer-algorithm and x-obs-server-side-encryption-customer-key-MD5.

No. This header is required when SSE-C is used. The key must be the same as that used to initiate multipart upload tasks.

x-obs-server-side-encryption-customer-key-MD5

Indicates the MD5 value of a key used to encrypt objects. The header is used in SSE-C mode. The MD5 value is used to check whether any error occurs during the transmission of the key.

Type: string

Example: x-obs-server-side-encryption-customer-key-MD5:4XvB3tbNTN+tIEVa0/fGaQ==

Constraint: This header is a Base64-encoded 128-bit MD5 value and must be used together with x-obs-server-side-encryption-customer-algorithm and x-obs-server-side-encryption-customer-key.

No. This header is required when SSE-C is used. The MD5 value must be the same as that used to initiate multipart upload tasks.

#### Request Elements

This request involves no elements.

#### Response Syntax

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    HTTP/1.1 status_code
    Date: date
    ETag: etag
    Content-Length: length

#### Response Headers

The response to the request uses common headers. For details, see Table 1.

Table 3 Additional response headers
Header | Description
--- | ---
x-obs-server-side-encryption | This header is included in a response if SSE-KMS is used. Type: string Example: x-obs-server-side-encryption:kms

x-obs-server-side-encryption-kms-key-id

Indicates the master key ID. This header is included in a response if SSE-KMS is used.

Type: string

Format: regionID:domainID:key/key_id

regionID is the ID of the region to which the key belongs. domainID is the account ID of the tenant to which the key belongs. key_id is the key ID used in this encryption.

Example: x-obs-server-side-encryption-kms-key-id:region:domainiddomainiddomainiddoma0001:key/4f1cd4de-ab64-4807-920a-47fc42e7f0d0

x-obs-server-side-encryption-customer-algorithm | Indicates an encryption algorithm. This header is included in a response if SSE-C is used. Type: string Example: x-obs-server-side-encryption-customer-algorithm:AES256
x-obs-server-side-encryption-customer-key-MD5 | Indicates the MD5 value of a key used to encrypt objects. This header is included in a response if SSE-C is used. Type: string Example: x-obs-server-side-encryption-customer-key-MD5:4XvB3tbNTN+tIEVa0/fGaQ==

#### Response Elements

This response involves no elements.

#### Error Responses

1. If a part number is not within the range from 1 to 10000, OBS returns 400 Bad Request.
2. If a part size has exceeded 5 GB, the error code 400 Bad Request is returned.
3. If the AK or signature is invalid, OBS returns 403 Forbidden and the error code is AccessDenied.
4. Check whether the bucket exists. If the bucket does not exist, OBS returns 404 Not Found and the error code is NoSuchBucket.
5. View the bucket ACL to check whether the user has the read permission for the requested bucket. If the user does not have the read permission, OBS returns 403 AccessDenied.
6. Check whether the multipart upload task exists. If the task does not exist, OBS returns 404 Not Found and the error code is NoSuchUpload.
7. Check whether the request user is the initiator of the multipart upload task. If not, OBS returns 403 Forbidden and the error code is AccessDenied.

Other errors are included in Table 2.

#### Sample Request

    PUT /object02?partNumber=1&uploadId=00000163D40171ED8DF4050919BD02B8 HTTP/1.1
    User-Agent: curl/7.29.0
    Host: examplebucket.obs.region.example.com
    Accept: */*
    Date: WED, 01 Jul 2015 05:15:55 GMT
    Authorization: OBS H4IPJX0TQTHTHEBQQCEC:ZB0hFwaHubi1aKHv7dSZjJts40g=
    Content-Length: 102015348

    [102015348 Byte part content]

#### Sample Response

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    HTTP/1.1 200 OK
    Server: OBS
    x-obs-request-id: 8DF400000163D40956A703289CA066F1
    ETag: "b026324c6904b2a9cb4b88d6d61c81d1"
    x-obs-id-2: 32AAAQAAEAABAAAQAAEAABAAAQAAEAABCUQu/EOEVSMa04GXVwy0z9WI+BsDKvfh
    Date: WED, 01 Jul 2015 05:15:55 GMT
    Content-Length: 0

Parent topic: Operations on Multipart Upload