Updated on 2024-01-25 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}

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

Table 1 Parameters in a URI

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. The endpoint varies between services in different regions. It can be obtained from Regions and Endpoints.

For example, the endpoint of IAM in region CN North-Beijing4 is iam.cn-north-4.myhuaweicloud.com.

resource-path

Access path of an API for performing a specified operation. Obtain the path 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. Not all APIs have a query parameter. Ensure that a question mark (?) is included before each 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 an IAM token in the CN North-Beijing4 region, obtain the endpoint of IAM (iam.cn-north-4.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:

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https://iam.cn-north-4.myhuaweicloud.com/v3/auth/tokens
Figure 1 Example URI

To simplify the URI display, 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

HTTP-based request methods, which are also called operations or actions, specifying the type of operations that you are requesting.
Table 2 HTTP methods

Method

Description

GET

Requests a server to return a specified resource.

PUT

Requests the server to update a specified resource.

POST

Requests a server to add a resource or perform a special operation.

DELETE

Requests a server to delete a specified resource (for example, an object).

HEAD

Requests a server resource header.

PATCH

Requests a server to update partial contents of a specified resource.

If the resource does not exist, a new resource will be created.

For example, in the case of the API used to obtain a user token, the request method is POST. The request is as follows:

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POST https://iam.cn-north-4.myhuaweicloud.com/v3/auth/tokens

Request Header

You can also add additional 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 lists common request header fields.
Table 3 Common request headers

Name

Description

Mandatory

Example Value

Host

Server domain name and port number of the resource being requested. The value can be obtained from the URL of the service API. The value is in the format of Hostname:Port number. If the port number is not specified, the default port is used. The default port number for HTTPS is 443.

No

This parameter is mandatory for AK/SK authentication.

code.test.com

or

code.test.com:443

Content-Type

Specifies the type (or format) of the message body. The default value application/json is recommended. Other values of this field will be provided for specific APIs if any.

Yes

application/json

Content-Length

Length of the request body. The unit is byte.

No

3495

X-Project-Id

Specifies a project ID. Obtain the project ID by following the instructions in Obtaining a Project ID.

No

This field is mandatory for requests that use AK/SK authentication in the Dedicated Cloud (DeC) scenario or multi-project scenario.

e9993fc787d94b6c886cbaa340f9c0f4

X-Auth-Token

User token.

It is a response to the API for obtaining a user token (This is the only API that does not require authentication).

After the request is processed, the value of X-Subject-Token in the response header is the token value.

No

Mandatory for token-based authentication.

The following is part of an example token:

MIIPAgYJKoZIhvcNAQcCo...ggg1BBIINPXsidG9rZ

In addition to supporting token-based authentication, cloud service APIs also 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, see "AK/SK-based Authentication" in Authentication.

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:

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POST https://iam.cn-north-4.myhuaweicloud.com/v3/auth/tokens
Content-Type: application/json

(Optional) Request Body

The request body is optional. A request body is often sent in a structured format (for example, JSON or XML) as defined in the Content-Type header field. If the request body contains full-width characters, these characters must be coded in UTF-8.

Request bodies vary with APIs. Some APIs do not require a 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 an example request with a body included. Replace username, domainname, ******** (login password), and xxxxxxxxxxxxxxxxxx (project name) with the actual values. Obtain a project name from Regions and Endpoints.

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.

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POST https://iam.cn-north-4.myhuaweicloud.com/v3/auth/tokens
Content-Type: application/json

{
    "auth": {
        "identity": {
            "methods": [
                "password"
            ],
            "password": {
                "user": {
                    "name": "username",
                    "password": "********",
                    "domain": {
                        "name": "domainname"
                    }
                }
            }
        },
        "scope": {
            "project": {
                "name": "xxxxxxxxxxxxxxxxxx"
            }
        }
    }
}

If all data required by a request is available, you can send the request to call the API through curl, Postman, or coding. For the API of obtaining a user token, x-subject-token in the response header is the required user token. Use the token to authenticate the calling of other APIs.