NAME

Action::CircuitBreaker - Module to try to perform an action, with an option to suspend execution after a number of failures.

VERSION

version 0.1

SYNOPSIS

  # Will execute the code, as the circuit will be closed by default.

  # OO interface
  use Action::CircuitBreaker;
  Action::CircuitBreaker->new()->run(sub { do_stuff; });

ATTRIBUTES

error_if_code

  ro, CodeRef

The code to run to check if the error should count towards the circuit breaker. It defaults to:

  # Returns true if there were an exception evaluating to something true
  sub { $_[0] }

It will be given these arguments:

• as first argument, a scalar which is the value of any exception that were raised by the $attempt_code. Otherwise, undef.

• as second argument, a HashRef, which contains these keys:

action_retry

it's a reference on the ActionRetry instance. That way you can have access to the other attributes.

attempt_result

It's a scalar, which is the result of $attempt_code. If $attempt_code returned a list, then the scalar is the reference on this list.

attempt_parameters

It's the reference on the parameters that were given to $attempt_code.

error_if_code return value will be interpreted as a boolean : true return value means the execution of $attempt_code was a failure and should count towards breaking the ciruit. False means it went well.

Here is an example of code that gets the arguments properly:

  my $action = Action::CircuitBreaker->new(
    error_if_code => sub {
      my ($error, $h) = @_;

      my $attempt_code_result = $h->{attempt_result};
      my $attempt_code_params = $h->{attempt_parameters};

      my @results = @$attempt_code_result;
      # will contains (2, 4);

      my @original_parameters = @$attempt_code_params;
      # will contains (1, 2);

    }
  );
  my @results = $action->run(sub { print @_; }, 1, 2);

on_failure_code

  ro, CodeRef, optional

If given, will be executed when an execution fails.

It will be given the same arguments as error_if_code. See error_if_code for their descriptions

on_circuit_open

  ro, CodeRef, optional

If given, will be executed the circuit gets opened.

It will be given the same arguments as error_if_code. See error_if_code for their descriptions

on_circuit_close

  ro, CodeRef, optional

If given, will be executed the circuit gets closed again.

It will be given no arguments

max_retries_number

  ro, int, optional

Maximum number of retries before opening circuit.

open_time

  ro, int, optional

Time in number of seconds to open the circuit for after max_retries_number have failed.

METHODS

run

Does the following:

step 1

Tests the value of _circuit_open_until. If it is positive and the current timestamp is before the value, an error is thrown, because the circuit is still open. If the value is positive, but before the current timestamp, the circuit is closed (by setting _circuit_open_until to 0) and optionally, on_circuit_close is run.

step 2

If the value of _circuit_open_until is 0, the circuit is closed, and the passed sub gets executed. Then it runs the error_if_code CodeRef in scalar context, giving it as arguments $error, and the return values of $attempt_code. If it returns true, we consider that it was a failure, and move to step 3. Otherwise, we consider it means success, and return the return values of $attempt_code.

step 3

Increase the value of _current_retries_number and check whether it is larger than max_retries_number. If it is, then open the circuit by setting _circuit_open_until to the current time plus open_time, and optionally run on_circuit_open. Then, die with the $error from $attempt_code.

step 4

Runs the on_failure_code CodeRef in the proper context, giving it as arguments $error, and the return values of $attempt_code, and returns the results back to the caller.

Arguments passed to run() will be passed to $attempt_code. They will also passed to on_failure_code as well if the case arises.

SEE ALSO

This code is heavily based on Action::Retry.

AUTHOR

hangy

COPYRIGHT AND LICENSE

This software is copyright (c) 2018 by hangy.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

cpanm Action::CircuitBreaker

perl -MCPAN -e shell
install Action::CircuitBreaker