Problem with Mojo::IOLoop timer before redirect

Question

i have a sub in my Mojolicious Controller which is called when a csv file is uploaded through a http post. After the file is uploaded, a message gets rendered that say "you will be redirected in x seconds". so i want to implement Mojo::IOLoop::Delay and as callback i use the redirect statement. But i get the following error by Morbo:

Mojo::Reactor::EV: Timer failed: Transaction already destroyed at /usr/local/share/perl/5.22.1/Mojolicious/Plugin/DefaultHelpers.pm line 168.

controller code:

sub upload {
    my $self = shift;
      # Check file size
      return $self->render(text => 'File is too big.', status => 200)
      if $self->req->is_limit_exceeded;

  # Process uploaded file
  return $self->redirect_to('/') unless my $newCsv = $self->param('fileToUpload');
  my $size = $newCsv->size;
  my $name = $newCsv->filename;
  my $delay = 2;
  $self->render(text => "Thanks for uploading $size byte file $name.<br>
    You will be redirected in $delay seconds");
  Mojo::IOLoop->timer($delay => sub {
    $self->redirect_to('/');
    });
}

relevant routes:

$r->get('/')->to(controller => 'main', action => 'index');
$r->post('/uploadCsv')->to(controller => 'main', action => 'upload')->name('uploadCsv');

Thank you in advance

score 3 · Answer 1 · answered Mar 08 '19 at 17:52

3

redirect_to is effectively a render that renders a HTTP 302 response to redirect. You cannot render twice, so even if you keep the transaction around until the redirect_to call, it would have already rendered the page. So there are two actual options for what you are trying to do; render a page with javascript that will perform the redirect after a timeout, or render an HTML page with a meta refresh tag which will cause the page to redirect after a delay. This MDN page discusses both approaches.

answered Mar 08 '19 at 17:52

Grinnz

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18

thanks for your answer. I have chosen the 3rd solution :) : i implemented a JS-script with a timeout in my .html. do you think this solution is practicable too, or it's not "the best" solution? – Chris Mar 08 '19 at 20:33
1

@Chris I think it's fine for what you want to accomplish, the only benefit of the meta-refresh approach is that it doesn't require the user to enable javascript. – Grinnz Mar 08 '19 at 20:36

score 1 · Accepted Answer · answered Mar 08 '19 at 08:30

upload returns after Mojo::IOLoop->timer and nothing waits for the timer. You can try using Mojo::IOLoop->delay and $delay->wait instead. But I am not sure how it works. So it might be equivalent to just sleep.

Do you really need to redirect from perl code? You can render some js with setTimeout for the same effect.

In fact I would recommend moving all text and redirecting to js and render only json with some status information inside upload. So you can implement better UI with error handling.

Problem with Mojo::IOLoop timer before redirect

2 Answers2