lemmy/src/root_span_builder.rs

use actix_web::{http::StatusCode, ResponseError};
use tracing::Span;
use tracing_actix_web::RootSpanBuilder;

// Code in this module adapted from DefaultRootSpanBuilder
// https://github.com/LukeMathWalker/tracing-actix-web/blob/main/src/root_span_builder.rs
// and root_span!
// https://github.com/LukeMathWalker/tracing-actix-web/blob/main/src/root_span_macro.rs

pub struct QuieterRootSpanBuilder;

impl RootSpanBuilder for QuieterRootSpanBuilder {
  fn on_request_start(request: &actix_web::dev::ServiceRequest) -> Span {
    let request_id = tracing_actix_web::root_span_macro::private::get_request_id(request);

    tracing::info_span!(
        "HTTP request",
        http.method = %request.method(),
        http.scheme = request.connection_info().scheme(),
        http.host = %request.connection_info().host(),
        http.target = %request.uri().path(),
        http.status_code = tracing::field::Empty,
        otel.kind = "server",
        otel.status_code = tracing::field::Empty,
        trace_id = tracing::field::Empty,
        request_id = %request_id,
        exception.message = tracing::field::Empty,
        // Not proper OpenTelemetry, but their terminology is fairly exception-centric
        exception.details = tracing::field::Empty,
    )
  }

  fn on_request_end<B>(
    span: tracing::Span,
    outcome: &Result<actix_web::dev::ServiceResponse<B>, actix_web::Error>,
  ) {
    match &outcome {
      Ok(response) => {
        if let Some(error) = response.response().error() {
          // use the status code already constructed for the outgoing HTTP response
          handle_error(span, response.status(), error.as_response_error());
        } else {
          let code: i32 = response.response().status().as_u16().into();
          span.record("http.status_code", code);
          span.record("otel.status_code", "OK");
        }
      }
      Err(error) => {
        let response_error = error.as_response_error();
        handle_error(span, response_error.status_code(), response_error);
      }
    };
  }
}

fn handle_error(span: Span, status_code: StatusCode, response_error: &dyn ResponseError) {
  let code: i32 = status_code.as_u16().into();

  span.record("http.status_code", code);

  if status_code.is_client_error() {
    span.record("otel.status_code", "OK");
  } else {
    span.record("otel.status_code", "ERROR");
  }

  // pre-formatting errors is a workaround for https://github.com/tokio-rs/tracing/issues/1565
  let display_error = format!("{response_error}");

  tracing::info_span!(
    parent: None,
    "Error encountered while processing the incoming HTTP request"
  )
  .in_scope(|| {
    if status_code.is_client_error() {
      tracing::warn!("{}", display_error);
    } else {
      tracing::error!("{}", display_error);
    }
  });

  span.record("exception.message", tracing::field::display(display_error));
}