Updated on 2023-11-20 GMT+08:00

Making an API Request

This section describes the structure of a REST API, and uses the IAM API for obtaining a user token as an example to demonstrate how to call an API. The obtained token is used to authenticate the calling of other APIs.

Request URI

A request URI is in the following format:

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

Although a request URI is included in a request header, most programming languages or frameworks require the request URI to be separately transmitted, rather than being conveyed in a request message.

Table 1 URI parameter description

Parameter

Description

URI-scheme

Protocol used to transmit requests. All APIs use HTTPS.

Endpoint

Domain name or IP address of the server bearing the REST service endpoint. Obtain the value from Endpoints.

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

resource-path

Resource path, that is, API access path.

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

(Optional) Query parameter. Not all APIs have a query parameter. 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 pieces of data is to be viewed.

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

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

To simplify the URI display in this document, each API is provided only with 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

The HTTP protocol defines the following request methods that can be used to send a request to the server:

Table 2 HTTP-defined request methods

Method

Description

GET

Requests the server to return specified resources.

PUT

Requests the server to update specified resources.

POST

Requests the server to add resources or perform special operations.

DELETE

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

HEAD

Same as GET except that the server must return only the response header.

PATCH

Requests the server to update partial content of a specified resource. If the resource does not exist, a new resource will be created.

In the case of the API used to obtain 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 also 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.

Common request header fields are as follows:

Table 3 Common request header fields

Parameter

Description

Mandatory

Example

X-Sdk-Date

Time when a request is sent, in YYYYMMDD'T'HHMMSS'Z' format.

The value is the current Greenwich Mean Time (GMT) of the system.

No

This field is mandatory for AK/SK-based authentication.

20150907T101459Z

Authorization

Signature authentication information.

The value can be obtained from the request signing result.

No

This field is 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

Requested server information, which can be obtained from the URL of a service API. The value is in hostname[:port] format. If the port number is not specified, the default port is used. The default port number for https is 443.

No

This field is mandatory for AK/SK-based authentication.

code.test.com

or

code.test.com:443

Content-Type

MIME type of the request body

Yes

application/json

Content-Length

Length of the request body. The unit is byte.

This parameter is 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 the token for each project.

No

e9993fc787d94b6c886cbaa340f9c0f4

X-Auth-Token

User token

No

This field is mandatory for token-based authentication.

-

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

For details about other fields in the header, see the HTTPS protocol documentation.

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 between APIs. Some APIs do not require the request body, such as the APIs requested using the GET and DELETE methods.

In the case of the API used to obtain a user token, the request parameters and parameter description can be obtained from the API request. The following provides a sample request with the body included. Set the username (username), account name (domainname), login password (********), and project name (xxxxxx). To learn how to obtain these values, see Obtaining Account, IAM User, and Project Information.

The scope parameter specifies where a token takes effect. You can set scope to an account or a project under an account. In the following example, the token takes effect only for the resources in a specified project. For more information about this API, 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": "username", 
                    "password": "********", 
                    "domain": { 
                        "name": "domainname" 
                    } 
                } 
            } 
        }, 
        "scope": { 
            "project": { 
                "name": "xxxxxx" 
            } 
        } 
    } 
}

If all data required for the API request is available, you can 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.