Warning message during global destruction

[Joel Berger]

I see that there is already a PR for a probably similar issue (#22) but I am getting a different error message:

(in cleanup) Can't call method "ping" on an undefined value at .../Mojo/mysql.pm line 82, line 307 during global destruction.

Manually I can suppress the warnings by changing line 82 from

while (my $c = shift @{$self->{queue} || []}) { return $c if $c->[0]->ping }

to

while (my $c = shift @{$self->{queue} || []}) { return $c if $c->[0] && $c->[0]->ping }

[Jan Henning Thorsen]

I don't get how you get into that situation: How come there's something doing _dequeue() on global destruction? From what I can see, only db() calls _dequeue(), which means that at some point your code is calling $mysql->db on global destruction..?

[Joel Berger]

I'm not terribly sure either. I'm taking over a codebase where it seems to happen quite regularly. I THINK it might be related to Minion::Backend::mysql.

[Jan Henning Thorsen]

I'm closing this because of inactivity. Please re-open if you have new information.

[Adrian Crisan]

Hi @jhthorsen

Got in the same situation. Below is some debug from my log file:

[Wed Nov 16 08:42:39 2016] [debug] Performing job "3" with task "test_task" in process 5803
[Wed Nov 16 08:42:39 2016] [warn] ================================================
[Wed Nov 16 08:42:39 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:39 2016] [warn] ================================================
[Wed Nov 16 08:42:39 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:41 2016] [debug] Reading configuration file "/apps/my_app/config/development.conf"
[Wed Nov 16 08:42:41 2016] [warn] ================================================
[Wed Nov 16 08:42:41 2016] [warn] $VAR1 = [
          undef,
          undef
        ];
[Wed Nov 16 08:42:41 2016] [warn]   (in cleanup) Can't call method "ping" on an undefined value at /apps/my_app/local/lib/perl5/Mojo/mysql.pm line 82, <DATA> line 307 during global destruction.
[Wed Nov 16 08:42:41 2016] [debug] Helper "user" already exists, replacing
[Wed Nov 16 08:42:41 2016] [warn] ================================================
[Wed Nov 16 08:42:41 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:41 2016] [warn] ================================================
[Wed Nov 16 08:42:41 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:41 2016] [warn] ================================================
[Wed Nov 16 08:42:41 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:41 2016] [debug] Performing job "4" with task "test_task" in process 5806
[Wed Nov 16 08:42:41 2016] [warn] ================================================
[Wed Nov 16 08:42:41 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:41 2016] [warn] ================================================
[Wed Nov 16 08:42:41 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:41 2016] [warn] ================================================
[Wed Nov 16 08:42:41 2016] [warn] $VAR1 = [
          bless( {}, 'DBI::db' ),
          undef
        ];
[Wed Nov 16 08:42:42 2016] [warn] ================================================
[Wed Nov 16 08:42:42 2016] [warn] $VAR1 = [
          undef,
          undef
        ];
[Wed Nov 16 08:42:42 2016] [warn]   (in cleanup) Can't call method "ping" on an undefined value at /apps/my_app/local/lib/perl5/Mojo/mysql.pm line 82, <DATA> line 307 during global destruction.

Those debug messages were produced by changing:

sub _dequeue {
  my $self = shift;
  my $dbh;

  while (my $c = shift @{$self->{queue} || []}) { return $c if $c->[0]->ping }

to

sub _dequeue {
  my $self = shift;
  my $dbh;

  use Data::Dumper;

  while (my $c = shift @{$self->{queue} || []}) {
    warn "================================================\n";
    warn Dumper($c);
    return $c if $c->[0]->ping
  }

Basically I'm having a minion worker running (script/my_app minion worker) and I have generate a list of 50 jobs.

My test job looks like this:

$app->minion->add_task(test_task => sub {
        my ($job, $args) = @_;


        sleep(5);
        $job->finish('Action complete.');
    });

And this is how I've loaded up minion:

my $config = $self->config->{ database };
    my $dsn = sprintf('%s://%s:%s@%s/%s', $config->{ driver }, $config->{ user }, $config->{ password }, $config->{ host }, $config->{ database });

    $self->plugin(Minion => {
        $config->{ driver } => $dsn
    });

Looks like changing this line

while (my $c = shift @{$self->{queue} || []}) { return $c if $c->[0]->ping }

to

while (my $c = shift @{$self->{queue} || []}) { return $c if $c->[0] && $c->[0]->ping }

fixes the issue.

Could you do this change please? Or should I create a pull request?

Cheers,
Adrian.

[Jan Henning Thorsen]

Sorry. My answer is still the same: I don't want to add patchwork without knowing what is causing this. Maybe Carp::Always can give more information? Like where is this coming from?

What I like about your comment @crlcu, is that you have a minimal test case, which should make it easier to pin down the issue. I will re-open later when you have provided more information.

[Andrii Nikitin]

I am getting this relatively frequently in my tests.

I don't get how you get into that situation: How come there's something doing _dequeue() on global destruction? From what I can see, only db() calls _dequeue(), which means that at some point your code is calling $mysql->db on global destruction..?

Yep your PubSub does it