Plack::Middleware::ContentLength

  # in app.psgi
  builder {
      enable "Plack::Middleware::ContentLength";
      $app;
  }
  # Or in Plack::Handler::*
  $app = Plack::Middleware::ContentLength->wrap($app);

Plack::Middleware::ContentLength is a middleware that automatically adds "Content-Length" header when it's appropriate i.e. the response has a content body with calculable size (array of chunks or a real filehandle).

This middleware can also be used as a library from PSGI server implementations to automatically set "Content-Length" rather than in the end user level.

Tatsuhiko Miyagawa

Rack::ContentLength