start recurring timer once with multiple workers

[Tim]

Hi,

is it possible to start a recurring timer only once when I have multiple workers?

So that I get this output

$ perl test.pl prefork -w 1
[Thu Jul  3 11:29:09 2014] [info] Listening at "http://*:3000".
Server available at http://127.0.0.1:3000.
[Thu Jul  3 11:29:09 2014] [info] Manager 1836 started.
[Thu Jul  3 11:29:09 2014] [debug] Worker 1837 started.
[Thu Jul  3 11:29:12 2014] [info] 0
[Thu Jul  3 11:29:15 2014] [info] 1
[Thu Jul  3 11:29:18 2014] [info] 2

instead of

$ perl test.pl prefork -w 4
[Thu Jul  3 11:29:28 2014] [info] Listening at "http://*:3000".
Server available at http://127.0.0.1:3000.
[Thu Jul  3 11:29:28 2014] [info] Manager 1838 started.
[Thu Jul  3 11:29:28 2014] [debug] Worker 1839 started.
[Thu Jul  3 11:29:28 2014] [debug] Worker 1840 started.
[Thu Jul  3 11:29:28 2014] [debug] Worker 1841 started.
[Thu Jul  3 11:29:28 2014] [debug] Worker 1842 started.
[Thu Jul  3 11:29:31 2014] [info] 0
[Thu Jul  3 11:29:32 2014] [info] 0
[Thu Jul  3 11:29:32 2014] [info] 0
[Thu Jul  3 11:29:32 2014] [info] 0
[Thu Jul  3 11:29:34 2014] [info] 1
[Thu Jul  3 11:29:35 2014] [info] 1
[Thu Jul  3 11:29:35 2014] [info] 1
[Thu Jul  3 11:29:35 2014] [info] 1
[Thu Jul  3 11:29:37 2014] [info] 2
[Thu Jul  3 11:29:38 2014] [info] 2
[Thu Jul  3 11:29:38 2014] [info] 2
[Thu Jul  3 11:29:38 2014] [info] 2

Code

use Mojolicious::Lite;

get '/' => sub {

    my $c = shift;

    $c->render(text => 'test');

};

sub start_recurring {

    my $i;

    Mojo::IOLoop->recurring(3 => sub {

      app->log->info($i++);

    });

}

start_recurring;

app->start;

[Stefan Adams]

On Thu, Jul 3, 2014 at 4:46 AM, Tim <ta1...@safe-mail.net> wrote:

is it possible to start a recurring timer only once when I have multiple workers?

I think I've seen a similar discussion in this forum before, but I can't find it.  IIRC, the final consensus was that for the requested behavior, the developer should be calling recurring from a Mojolicious::Command and execute it from the command line or cron and not calling this "maintenance code" from a Controller where its execution is dependent on a connecting client.

Sorry if I'm wrong.  HTH!

[Jan Henning Thorsen]

Could you rather explain what the actual problem that you're trying to solve is?

Maybe the answer is a cron-job :)

I've implemented some really awful locking mechanism in Convos to only start a piece of code in one child. It creates a lock in the Redis database to prevent the other children from running the same code. https://metacpan.org/source/JHTHORSEN/Convos-0.6/lib/Convos.pm#L323

What is important is that the lock need to be atomic. symlink() and $handle->open($name, O_CREAT | O_EXCL) and friends are atomic, but you need to be cautious about hypnotoad and "hot reload", or just the fact that the child that started the recurring timer might die. 

[Per Carlson]

Hi.

This thread might be the one you are thinking of:
https://groups.google.com/forum/#!topic/mojolicious/UK6oHtJBIcQ

[Tim]

Thanks, but I want to do it without a cron job in a single Mojolicious::Lite app.

Do you think this is a viable solution?

Mojo::IOLoop->next_tick(sub {
    if(! -e 'timer.running') {
        open my $fh, '>', 'timer.running' or die $!;
        app->log->debug('timer created');

        Mojo::IOLoop->recurring(1 => sub {
            #...
        });
    }
});