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  2. Flex Gateway Policy Development Kit (PDK) (1.2)
  3. Implementing Your Custom Policy Features in Rust

  4. Sharing Data Between Requests and Responses

Sharing Data Between Requests and Responses

Flex Gateway Policy Development Kit (PDK) provides the RequestData enum to pass data between the request and the response.

To share a status between the request and the response functions, the request function must return a Flow::Continue enum variant with a data parameter that that you wish to pass to the response function. The response function must receive the RequestData parameter that contains the request function’s final status and the data parameter that was passed.

The RequestData enum has the following possible final status:

  • RequestData::Continue(data): The request function ended with Flow::Continue(data).

  • RequestData::Break : The request function ended with Flow::Break.

  • RequestData::Cancel: The request function was cancelled.

If the request function ended with a Flow::Continue and was not cancelled by upstream policies, the RequestData::Continue variant contains the value sent by the request function.

Implement this by adding an on_response wrapped function to the Flow example used in Stopping Request Execution:

async fn request_filter(state: RequestState) -> Flow<String> {
    let state = state.into_headers_state().await;
    let handler = state.handler();
    if handler.header("authorization").is_some() {
        Flow::Continue(state.path())
    } else {
        Flow::Break(
            Response::new(401)
                .with_headers(vec![(
                    "WWW-Authenticate".to_string(),
                    "Bearer realm=\"oauth2\"".to_string(),
                )])
                .with_body(r#"{ "error": "token was not present"}"#),
        )
    }
}

async fn response_filter(state: ResponseState, request_data: RequestData<String>) {
    // Handle only completed requests
    if let RequestData::Continue(path) = request_data else {
        return;
    };

    let state = state.into_headers_state().await;
    logger::info!("Path: {path}, Status: {}", state.status_code());
}

See Also