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

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 for the REST service endpoint. The endpoint varies depending on services in different regions. It can be obtained in Endpoints. For example, the endpoint of IAM in the CN-Hong Kong region is iam.ap-southeast-1.myhuaweicloud.com. NOTE: Use iam-endpoint to obtain a token (iam-apigateway-proxy.{region_id}.{external_domain_name}). Configure the domain name in the format of "{float_ip} iam-apigateway-proxy.{region_id}.{external_domain_name}" in the hosts file on the local PC. For details, see Obtaining a User Token.
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 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
Click to enlarge

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

HTTP 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	Requests the server to return 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 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 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.

Table 3 describes common request header fields.

**Table 3** Common request headers
Parameter	Description	Mandatory	Example Value
Content-type	Request body type or format. The default value is application/json.	Yes	application/json
Content-Length	Length of the request body. The unit is byte.	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	The user token is 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	-
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) 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	Information about the requested server. The value can be obtained from the URL of the service API. The value is in the format of hostname:port. 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 more information about AK/SK-based authentication, see AK/SK Signing and Authentication 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 request with the request body added is as follows. Replace the italic fields in bold with the actual values. user_name indicates the username, domain_name indicates the account name, user_password indicates the login password, and ap-southeast-1 indicates the project name. For details about how to obtain the project name, see Obtaining a Username and ID, Obtaining an Account Name and Account ID, and Obtaining a Username.

The scope parameter specifies where a token takes effect. In the example, the token takes effect only for the resources in a specified project. MaaS 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.

Parent topic:Calling APIs

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Next topic: Authentication

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