http_request_post plugin

Article
08/12/2024

Applies to: ✅ Microsoft Fabric ✅ Azure Data Explorer

The http_request_post plugin sends an HTTP POST request and converts the response into a table.

Prerequisites

Run .enable plugin http_request_post to enable the plugin
Set the URI to access as an allowed destination for webapi in the Callout policy

Syntax

evaluate http_request_post ( Uri [, RequestHeaders [, Options [, Content]]] )

Learn more about syntax conventions.

Parameters

Name	Type	Required	Description
Uri	`string`	✔️	The destination URI for the HTTP or HTTPS request.
RequestHeaders	`dynamic`		A property bag containing HTTP headers to send with the request.
Options	`dynamic`		A property bag containing additional properties of the request.
Content	`string`		The body content to send with the request. The content is encoded in `UTF-8` and the media type for the `Content-Type` attribute is `application/json`.

Note

To specify an optional parameter that follows an optional parameter, make sure to provide a value for the preceding optional parameter. For more information, see Working with optional parameters.
If you're using authentication, use the HTTPS protocol. Attempts to use HTTP with authentication results in an error.

Authentication and authorization

To authenticate, use the HTTP standard Authorization header or any custom header supported by the web service.

Note

If the query includes confidential information, make sure that the relevant parts of the query text are obfuscated so that they'll be omitted from any tracing. For more information, see obfuscated string literals.

Returns

The plugin returns a table that has a single record with the following dynamic columns:

ResponseHeaders: A property bag with the response header.
ResponseBody: The response body parsed as a value of type dynamic.

If the HTTP response indicates (via the Content-Type response header) that the media type is application/json, the response body is automatically parsed as-if it's a JSON object. Otherwise, it's returned as-is.

Headers

The RequestHeaders argument can be used to add custom headers to the outgoing HTTP request. In addition to the standard HTTP request headers and the user-provided custom headers, the plugin also adds the following custom headers:

Name	Description
`x-ms-client-request-id`	A correlation ID that identifies the request. Multiple invocations of the plugin in the same query will all have the same ID.
`x-ms-readonly`	A flag indicating that the processor of this request shouldn't make any persistent changes.

Warning

The x-ms-readonly flag is set for every HTTP request sent by the plugin that was triggered by a query and not a management command. Web services should treat any requests with this flag as one that does not make internal state changes, otherwise they should refuse the request. This protects users from being sent seemingly-innocent queries that end up making unwanted changes by using a Kusto query as the launchpad for such attacks.

Example

The following example is for a hypothetical HTTPS web service that accepts additional request headers and must be authenticated to using Microsoft Entra ID:

Kusto

let uri='https://example.com/node/js/on/eniac';
let headers=dynamic({'x-ms-correlation-vector':'abc.0.1.0', 'authorization':'bearer ...Azure-AD-bearer-token-for-target-endpoint...'});
evaluate http_request_post(uri, headers)

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