Help Center/ ModelArts/ API Reference/ Calling APIs/ Making an API Request
Updated on 2025-08-20 GMT+08:00

Making an API Request

This section describes the structure of a REST API request, and uses the IAM API for Obtaining a User Token as an example to demonstrate how to call an API. The obtained token can then be used to authenticate the calling of other APIs.

Request URI

The format of a request URI is as follows:

{URI-scheme} :// {Endpoint} / {resource-path} ? {query-string}

Table 1 Request URI

Parameter

Description

URI-scheme

Protocol used to transmit requests. All APIs use HTTPS.

Endpoint

Domain name or IP address of the server for the REST service endpoint. The endpoint varies depending on services in different regions. It can be obtained in Endpoint.

For example, the endpoint of IAM in the CN-Hong Kong region is iam.ap-southeast-1.myhuaweicloud.com.

resource-path

Access path of an API for performing a specified operation. Obtain the value from the URI of an API. For example, the resource-path of the API used to obtain a user token is /v3/auth/tokens.

query-string

Query parameter, which is optional. Ensure that a question mark (?) is included before a query parameter that is in the format of "Parameter name=Parameter value". For example, ? limit=10 indicates that a maximum of 10 data records will be displayed.

For example, to obtain a token in the CN-Hong Kong region, obtain the endpoint of IAM (iam.ap-southeast-1.myhuaweicloud.com) for this region and the resource-path (/v3/auth/tokens) in the URI of the API used to obtain a user token. Then, construct the URI as follows:

https://iam.ap-southeast-1.myhuaweicloud.com/v3/auth/tokens
Figure 1 Example URI

To simplify the URI display, each API is provided with only a resource-path and a request method. The URI-scheme of all APIs is HTTPS, and the endpoints of all APIs in the same region are identical.

Request Methods

HTTP defines the following request methods that can be used to send a request to the server.

Table 2 HTTP methods

Method

Description

GET

Request the server to return specified resources.

PUT

Request the server to update specified resources.

POST

Request the server to add resources or perform special operations.

DELETE

Request the server to delete specified resources, for example, an object.

HEAD

Request header.

PATCH

Request the server to update partial content of a specified resource.

If the requested resource does not exist, the server may create the resource using the PATCH method.

For example, in the URI of the API for obtaining a user token, the request method is POST. The request is as follows:
POST https://iam.ap-southeast-1.myhuaweicloud.com/v3/auth/tokens

Request Header

You can add additional header fields to a request, such as the fields required by a specified URI or HTTP method. For example, to request for the authentication information, add Content-Type, which specifies the request body type.

Table 3 describes common request header fields.

Table 3 Common request headers

Parameter

Description

Mandatory

Example

Content-type

Request body type or format. The default value is application/json.

Yes

application/json

Content-Length

Length of the request body, in bytes.

Mandatory for POST and PUT requests but must be left blank for GET requests

3495

X-Project-Id

Project ID. This parameter is used to obtain a token for each project.

No

e9993fc787d94b6c886cbaa340f9c0f4

X-Auth-Token

User token, a response to the API used to obtain a user token. This API is the only one that does not require authentication.

Mandatory for token-based authentication

N/A

X-Sdk-Date

Time when the request is sent. The time is in YYYYMMDD'T'HHMMSS'Z' format.

The value is the current GMT time of the system.

Mandatory for AK/SK-based authentication, optional for PKI token-based authentication

20190307T101459Z

Authorization

Authentication information.

The value is obtained from the request signature result and is required when the AK/SK are used to encrypt the signature.

Type: string

Default value: none

Mandatory for AK/SK-based authentication

SDK-HMAC-SHA256 Credential=ZIRRKMTWPTQFQI1WKNKB/20150907//ec2/sdk_request, SignedHeaders=content-type;host;x-sdk-date, Signature=55741b610f3c9fa3ae40b5a8021ebf7ebc2a28a603fc62d25cb3bfe6608e1994

Host

Server information of the resource being requested. The value can be obtained from the URL of the service API.

This value is host name[:port number].

If the port number is not specified, the default port is used. The default port number for https is 443.

Mandatory for AK/SK-based authentication

code.test.com

or

code.test.com:443

In addition to supporting token-based authentication, APIs support authentication using AK/SK. During AK/SK authentication, an SDK is used to sign a request, and the Authorization (signature authentication) and X-Sdk-Date (time when a request is sent) headers are automatically added to the request. For details about AK/SK authentication, see API Request Signing Guide.

The API used to obtain a user token does not require authentication. Therefore, only the Content-Type field needs to be added to requests for calling the API. An example of such requests is as follows:
POST https://iam.ap-southeast-1.myhuaweicloud.com/v3/auth/tokens
Content-Type: application/json

Request Body

The body of a request is often sent in a structured format as specified in the Content-Type header field. The request body transfers content except the request header. If the request body contains Chinese characters, these characters must be encoded in UTF-8.

The request body varies depending on APIs. Some APIs do not require the request body, such as the APIs requested using the GET or DELETE method.

If an API is used to obtain a user token, the request parameters and parameter description can be obtained from the API request. The following provides an example request with a body included. Replace user_name, domain_name, and user_password with the actual username, account name, and login password, respectively. ap-southeast-1 is the project name. For details, see Obtaining a Username, Obtaining an Account Name and ID, and Obtaining a Project Name.

The scope parameter specifies where a token takes effect. In the example, the token takes effect only for the resources in a specified project. ModelArts uses a region-specific endpoint to call this API. Set scope to project. You can set scope to an account or a project under an account. For details, see Obtaining a User Token.

POST https://iam.ap-southeast-1.myhuaweicloud.com/v3/auth/tokens
Content-Type:application/json
{
  "auth": {
    "identity": {
      "methods": ["password"],
      "password": {
        "user": {
          "name": "user_name", 
          "password": "user_password",
          "domain": {
            "name": "domain_name"  
          }
        }
      }
    },
    "scope": {
      "project": {
        "name": "ap-southeast-1"  
      }
    }
  }
}

After all data required for the API request is available, send the request to call the API through curl, Postman, or coding. In the response to the API used to obtain a user token, x-subject-token is the desired user token. This token can then be used to authenticate the calling of other APIs.