Updated on 2022-08-09 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 describe 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 the request header, most programming languages or frameworks require the request URI to be transmitted separately.

Table 1 URI parameter description




Protocol used to transmit requests. All APIs use HTTPS.


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 the administrator.


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 pieces of data is to be viewed.


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




Requests the server to return specified resources.


Requests the server to update specified resources.


Requests the server to add resources or perform special operations.


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


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


Requests the server to update partial content of a specified resource.

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

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






Specifies the time when the request is sent. The time is in YYYYMMDD'T'HHMMSS'Z' format.

The value is the current GMT time of the system.


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



Specifies signature authentication information.

The value can be obtained from the request signing result.


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


Specifies the server domain name and port number of the resource being requested. The value can be obtained from the URL of a 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.


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





Specifies the MIME type of the request body.




Specifies the length of the request body. The unit is byte.

This field is mandatory for POST and PUT requests, but must be left blank for GET requests.



Specifies the project ID. This field is used to obtain the token for each project.

This field is mandatory for the request from a DeC or multi-project user.




Specifies the user token.


This field is mandatory for token-based authentication.


In addition to supporting token-based authentication, 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 details about other fields in the header, see the HTTPS protocol documentation.

Request Body

The body of a request is often sent in a structured format (JSON or XML) as specified in the Content-Type header field. The request body transfers content except the request header.

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 (xxxxx).

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

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

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.