New Perl module: Action::Retry

January 21, 2013

UPDATE: I have included a functional API, as per Oleg Komarov request, and amended this post accordingly.

I’ve just released a new module called Action::Retry.

Use it when you want to run some code until it succeeds, waiting between two retries.

A simple way to use it is :

use Action::Retry qw(retry);
retry { ... };

And the Object Oriented API:

Action::Retry->new( attempt_code => sub { ... } )->run();

The purpose of this module is similar to Retry, Sub::Retry, Attempt and AnyEvent::Retry. However, it’s highly configurable, more flexible and has more features.

You can specify the code to try, but also a callback that will be executed to check the success or failure of the attempt. There is also a callback to execute code on failure.

The module also supports different sleep strategies ( Constant, Linear, Fibonacci…) and it’s easy to build yours. Strategies can have their options as well.

my $action = Action::Retry->new(
  attempt_code => sub { ... },
  retry_if_code => sub { $_[0] =~ /Connection lost/ || $_[1] > 20 },
  strategy => { Fibonacci => { multiplicator => 2000,
                               initial_term_index => 3,
                               max_retries_number => 5,
                             }
              },
  on_failure_code => sub { say "Given up retrying" },
);
$action->run();

And the functional API:

  use Action::Retry qw(retry);
  retry { ... }
  retry_if_code => sub { $_[0] =~ /Connection lost/ || $_[1] > 20 },
  strategy => { Fibonacci => { multiplicator => 2000,
                               initial_term_index => 3,
                               max_retries_number => 5,
                             }
              },
  on_failure_code => sub { say "Given up retrying" };

Strategies can decide if it’s worthwhile continuing trying, or if it should fail.

Action::Retry also supports a pseudo “non-blocking” mode, in which it doesn’t actually sleep, but instead returns immediately, and won’t perform the action code until required time has elapsed. Basicaly it allows to do this:

my $action = Action::Retry->new(
  attempt_code => sub { ... },
  non_blocking => 1,
  strategy => { 'Constant' }
);
while (1) {
  # if the action failed, it doesn't sleep
  # next time it's called, it won't do anything until it's time to retry
  $action->run();

  do_something_else();
  # do something else while time goes on

}

of course do_something_else should be very fast, so that the loop goes back quickly to retrying the attempt_code.

Action::Retry is based on Moo for performance (and because the module is simple enough to not require Moose). Moo classes properly expand to Moose ones if needed, so there is no excuse not to use it.

So, please give a try to Action::Retry, and let me know what you think.

---