Updated on 2022-09-15 GMT+08:00

Making an API Request

This section describes the structure of a REST API and how to call an API. Before calling an API, you need to obtain the user token using the IAM API.

Request URI

A request URI is in the following format:

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

Although a request URI is a part of 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. The endpoint varies depending on the service and service region. Endpoint: Endpoint of the Objective-func function. For details, see Regions and Endpoints.

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. 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.

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

To simplify the URI display, each API is provided only with a resource-path and a request method. This is because the URI-scheme value of all APIs is HTTPS, and the endpoints in a region are the same. Therefore, the two parts are omitted.

Request Method

HTTP methods, which are also called operations or actions, specify the type of operations that you are requesting.
Table 2 HTTP methods

Method

Description

GET

Requests a server to return specified resources.

PUT

Requests a server to update specified resources.

POST

Requests the server to add a resource or perform special operations.

DELETE

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

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

1
POST https://{{Endpoint}}/v3/auth/tokens

Request Headers

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.

You can also add additional fields to the request header, for example, the fields required by a specified URI and an HTTP method. Table 3 lists common request header fields.

Table 3 Common request headers

Field

Description

Mandatory

Example

Host

Requested server information, which can be obtained from the URL of the service API. The value is in the 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 parameter is mandatory for AK/SK authentication.

code.test.com

or

code.test.com:443

Content-Type

MIME type of the request body. You are advised to use the default value application/json. For APIs used to upload objects or images, the value varies depending on the flow type.

Yes

application/json

Content-Length

Length of the request body. The unit is byte.

This parameter is optional for POST requests, but must be left blank for GET requests.

3495

X-Project-Id

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

No

This parameter 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

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

No

This parameter is mandatory for token authentication.

The following is part of an example token:

MIIPAgYJKoZIhvcNAQcCo...ggg1BBIINPXsidG9rZ

In addition to supporting token-based authentication, APIs support authentication using access key ID/secret access key (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.

The API used to obtain a user token does not require authentication. Therefore, this API only requires adding the Content-Type field. The request with the added Content-Type header is as follows:

POST https://{{endpoint}}/v3/auth/tokens
Content-Type: application/json

(Optional) Request Body

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

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

For the API used to obtain a user token, the request parameters and parameter description can be obtained in the API request. The following provides an example request with a body included. Replace username, domainname, ******** (login password), and xxxxxxxxxxxxxxxxxx (project name such as ) with actual values. You can obtain the values from the administrator.

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.

POST https://{{endpoint}}/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 for the API 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. This token can then be used to authenticate the calling of other APIs.

Initiating Requests

You can initiate a request based on the constructed request message in one of the following ways:

  • cURL

    cURL is a command-line tool used to perform URL operations and transmit information. It serves as an HTTP client that can send HTTP requests to the server and receive response messages. cURL is used for API debugging. For more information about cURL, visit https://curl.haxx.se/.

    For security purposes, run the curl command on the server to query information, and then clear operation records, including but not limited to records in the ~/.bash_history and /var/log/messages directories (if any).

  • Code

    You can call APIs using code to assemble, send, and process request messages.

  • REST client

    Both Mozilla Firefox and Google Chrome provide a graphical browser plug-in, REST client, to send and process requests. For Mozilla Firefox, see Firefox REST Client. For Google Chrome, see Chrome REST Client.