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.