Handle async routes in the Mojolicious plugin

[rabbiveesh]

Because the sentry integrations are global, they don't play nicely out of the box with async; in my project at work i've written my own sentry plugin around this one that uses Syntax::Keyword::Dynamically and Future::AsyncAwait to solve this, relevant bits below -

  $app->hook(
    around_action => sub ($next, $c, $action, $last) {
      my $req = $c->req;

      my $scope       = $c->stash('_sentry_scope');
      my $transaction = $c->stash('_sentry_transaction');
      unless ($scope) {

        # eliminate any non-request scopes, b/c memory leaks for the lose
        Sentry::Hub->get_current_hub->reset;
        Sentry::SDK->configure_scope(sub ($new_scope) {
          my $transaction = Sentry::SDK->start_transaction({
            name    => $c->match->endpoint->to_string // '/',
            op      => 'http.server',
            request => {
              url     => $req->url->to_abs->to_string,
              method  => $req->method,
              query   => $req->url->query->to_hash,
              headers => { pairgrep { $a ne 'Cookie' } $req->headers->to_hash->%* }
            },
            $self->continue_from_headers($req->headers)->%*
          });
          $new_scope->set_span($transaction);

          $c->stash(_sentry_scope       => $scope = $new_scope);
          $c->stash(_sentry_transaction => $transaction);
        });
      }

      # save our scope for this dynamic context
      dynamically Sentry::Hub->get_current_hub->{scopes} = [$scope];

      # turn on breadcrumbs for this dynamic context
      dynamically Sentry::Integration->get_integration('DBI')->{breadcrumbs}           = 1;
      dynamically Sentry::Integration->get_integration('MojoUserAgent')->{breadcrumbs} = 1;

      return $next->() if $c->tx->is_websocket;

      # always returns a promise
      $self->handle_action($c, $next, $last);

      # break the dispatch chain, but the action handler may actually continue it
      return $last;
    }
  );

and the call to handle_action is

async sub handle_action ($self, $c, $next_hook, $last) {
  # we must hold onto the $tx here, b/c the req may get cancelled while await-ing
  my $tx;
  try {
    $tx = $c->render_later->tx;
    my $fin = $next_hook->();
    $fin = await $fin if blessed $fin and $fin->can('AWAIT_IS_READY');

    # we need to delay to avoid an infinite loop
    Mojo::IOLoop->next_tick(sub {
      $c->continue if $fin && !$last;
    });
  } catch ($err) {
    $c->reply->exception($err);
    Sentry::SDK->capture_exception($err) if $c->res->is_server_error;
  } finally {
    if ($last) {
      my $transaction = $c->stash('_sentry_transaction');
      if (defined $c->stash('sentry_tracing')) {
        $transaction->sampled($c->stash('sentry_tracing'));
      }
      $transaction->set_http_status($c->res->code) if $c->res->code;
      $transaction->finish();
    }
  }
}

Would be happy to open a PR, just wanna know if the dependencies are acceptable for the scope of this project.

[pmb0]

Hi, I've never used async in Perl (and never will in the future) -- if your changes don't cause problems with the blocking variant, I'd merge them.