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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.

You can also learn how to construct a request to call an API through the video tutorial.

Request URI

A request URI is in the following format:

{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 bearing the REST service. The endpoint varies between services in different regions. It can be obtained from Endpoints.

For example, the endpoint of IAM in the CN North-Beijing4 region 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. 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 CN North-Beijing4, 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:

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

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 Method

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

Table 2 HTTP 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.
For example, 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.cn-north-4.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.

Table 3 describes common request header fields.

Table 3 Common request header fields

Parameter

Description

Mandatory

Example Value

Content-type

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

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

No

This parameter is mandatory for token 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 Greenwich Mean Time (GMT) of the system.

No

If AK and SK are used for API authentication, this parameter must be configured. If PKI token is used, you do not need to configure this parameter.

20190307T101459Z

Authorization

Signature authentication information.

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

Type: string

Default value: none

No

This parameter is mandatory for AK/SK authentication.

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

Host

Information about the requested server. The value can be obtained from the URL of the service API.

The value is hostname[:port].

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

In addition to supporting token-based authentication, public cloud APIs also 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 details, see API Request Signing Guide.

For example, 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.cn-north-4.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 coded 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 an example request with a body included. Replace username, domainname, and ******** (login password) with the actual values. cn-north-4 indicates the project name. To learn how to obtain your username, account name, and project ID, see Obtaining the Username, Account Name, and Project Name.

  • The scope parameter specifies where a token takes effect. Its value can be project or domain. In the preceding example, the value of scope is project, indicating that the obtained token can access only resources of the specified project. If the value of scope is domainname, the obtained token can access all resources of the specified account. For details, see Obtaining a User Token.
  • project name: On the My Credentials page, the value in the Project column is the project name. For details about how to obtain the project name, see Obtaining the Username, Account Name, and Project Name.
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": "cn-north-4"  
      }
    }
  }
}

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.

Parent topic: Calling APIs