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  2. Flex Gateway Policy Development Kit (PDK) (1.1)
  3. Implementing Your Custom Policy Features in Rust

  4. Performing an HTTP Call

Performing an HTTP Call

To view an example policy project that makes HTTP calls, see Simple OAuth 2.0 Validation Policy Example.

To interact with external services, the policy must use HTTP calls. You can only make HTTP calls from the request filter or the response filter.

To perform an HTTP call, either inject the HTTPClient into the [entrypoint] function or the wrapper functions:

  • Injecting the client parameters into the [entrypoint] function enables you to make calls in both the request and the response filter:

    #[entrypoint]
async fn configure(launcher: Launcher, Configuration(bytes): Configuration, client: HttpClient) -> Result<()> {
    let config: Config = serde_json::from_slice(&bytes).unwrap();

    // Both request and the response handlers will use the client
    let filter = on_request(|request_state| request_filter(request_state, &config, &client))
        .on_response(|response_state, request_data| {
            response_filter(response_state, request_data, &config, &client)
        });

    launcher.launch(filter).await?;
    Ok(())
}

  • Injecting the client parameters into one of the on_request or on_response wrapper functions enables you to only make calls in that function:

    // Handler with the logic for incoming requests
​​async fn request_filter(state: RequestState, conf: &Config, client: HttpClient) {
 ...
}

#[entrypoint]
async fn configure(launcher: Launcher, Configuration(bytes): Configuration) -> Result<()> {
    let config: Config = serde_json::from_slice(&bytes).unwrap();

    // For incoming request events, using the on_request wrapper, inject the client and pass it to the request_filter handler
    launcher
        .launch(on_request(|request, client| {
            request_filter(request, &config, client)
        }))
        .await?;
    Ok(())
}

You must define your service as a parameter in your schema definition to make HTTP requests. To learn more about defining parameters, see Defining a Policy Schema Definition

The following code snippet provides an example schema definition for an external service:

properties:
      externalService:
          type: string
          format: service
      endpointPath:
          type: string

In the policy’s Rust source code, you can access the defined external service in the Config struct. To perform requests, call the HTTP client in your policy, for example:

let response = client
    .request(&config.external_service)
    .path(&config.endpoint_path)
    .headers(vec![("Content-Type", "application/json")])
    .body(r#"{"key": "value"}"#.as_bytes())
    .put().await?;

See Also