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 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}

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
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 between services in different regions. An endpoint is the request address for calling an API. Endpoints vary depending on services and regions. You can obtain endpoints from Endpoints. For example, the endpoint of IAM in the EU-Dublin region is iam.eu-west-101.myhuaweicloud.eu.
resource-path	Access path of an API for performing a specified operation. Obtain the value 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, it indicates that a maximum of 10 data records are allowed.

For example, to obtain an IAM token in the EU-Dublin region, obtain the endpoint of IAM (iam.eu-west-101.myhuaweicloud.eu) 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.eu-west-101.myhuaweicloud.eu/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 value 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.eu-west-101.myhuaweicloud.eu/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 the authentication information, add Content-Type, which specifies the request body type.

Table 3 lists common request header fields.

**Table 3** Common request header fields
Field	Description	Mandatory	Example
Content-Type	Specifies the request body MIME type. This field is mandatory and its default value is application/json. Other values of this field will be provided for specific APIs if any.	Yes	The default value is application/json.
Content-Length	Specifies the length of the request body. The unit is byte.	No	3495
X-Language	Specifies the request language.	No	en_us
X-Project-Id	Specifies a project ID. Obtain the project ID by following the instructions in Project ID and Account ID.	No	e9993fc787d94b6c886cbaa340f9c0f4
X-Auth-Token	Specifies a user 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. The token is the value of X-Subject-Token in the response header.	This field is mandatory for token authentication.	The following is part of an example token: MIIPAgYJKoZIhvcNAQcCo...ggg1BBIINPXsidG9rZ
X-Sdk-Date	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.	20150907T101459Z
Host	Specifies the server domain name and port number of the resources being requested. 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.	This field is mandatory for AK/SK-based authentication.	code.test.com or code.test.com:443
Authorization	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=QRUP2R3QFNAOVAWMYHZW/20160202/northchina/test/sdk_request, SignedHeaders=host;x-sdk-date, Signature=9d8b56b055c0e1f7a9498d881a7cb726be91b4f0cde1773b0b1557e987a480ce
workspace	Workspace ID. For details about how to obtain it, see DataArts Studio Instance ID and Workspace ID.	You do not need to set this field when calling a CDM API because in that case, only the default workspace can be used. When a DataArts Factory API is called, data in the default workspace is queried by default. To query data in other workspaces, include this header in the query request. This header is mandatory for calling the APIs of other modules. Otherwise, API calls will fail.	d1cd7861478748a6925bc02f47c69279
X-Dlm-Type	DataArts DataService edition, which is Exclusive	This parameter is mandatory for calling DataArts DataService APIs.	EXCLUSIVE: exclusive edition

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 authentication) 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:

POST https://iam.eu-west-101.myhuaweicloud.eu/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.

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, ******** (login password), and xxxxxxxxxxxxxxxxxx (project ID) with the actual values. To learn how to obtain a project ID, see Project ID and Account ID.

The scope parameter specifies where a token takes effect. You can set scope to an account or a project under an account. For details, see Obtaining a User Token.

POST https://iam.eu-west-101.myhuaweicloud.eu/v3/auth/tokens
Content-Type: application/json

{
    "auth": {
        "identity": {
            "methods": [
                "password"
            ],
            "password": {
                "user": {
                    "name": "username",
                    "password": "********",
                    "domain": {
                        "name": "domainname"
                    }
                }
            }
        },
        "scope": {
            "project": {
                "id": "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 used to obtain a user token, x-subject-token in the response header is the desired user token. This token can then be used to authenticate the calling of other APIs.

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