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lib/Algorithm/Backoff/RetryTimeouts.pm  view on Meta::CPAN

        summary => 'How much randomness to add to the adjustable timeout',
        schema  => ['float*', between=>[0, 0.5]],
        default => 0.1,
    };
}

#pod =head1 CONSTRUCTOR
#pod
#pod The L<"new"|Algorithm::Backoff::Exponential/new> constructor takes all of the base options
#pod from L<Algorithm::Backoff::Exponential>. Some of the defaults are changed (also shown in
#pod the L</SYNOPSIS> above), but otherwise function the same way.
#pod
#pod =over
#pod
#pod =item * L<max_attempts|Algorithm::Backoff::Exponential/new> => I<uint> (default: 8)
#pod
#pod =item * L<max_actual_duration|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: 50)
#pod
#pod =item * L<jitter_factor|Algorithm::Backoff::Exponential/new> => I<float> (default: 0.1)
#pod
#pod =item * L<initial_delay|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: C<sqrt(2)>)
#pod
#pod =item * L<exponent_base|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: C<sqrt(2)>)
#pod
#pod =item * L<delay_on_success|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: 0)
#pod
#pod =item * L<min_delay|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: 0)
#pod
#pod =item * L<max_delay|Algorithm::Backoff::Exponential/new> => I<ufloat>
#pod
#pod =item * L<consider_actual_delay|Algorithm::Backoff::Exponential/new> => I<bool> (default: 1)
#pod
#pod =back
#pod
#pod The following new options are added in this module:
#pod
#pod =over
#pod
#pod =item * adjust_timeout_factor => I<ufloat> (default: 0.5)
#pod
#pod How much of the remaining time to use for the next attempt's timeout, as a
#pod factor between 0 and 1.
#pod
#pod In order to prevent a single attempt from using up all of the remaining time, an
#pod adjustable timeout will force the attempt to only use a portion of the time.  By default,
#pod only 50% of the remaining time will be set as the next timeout value.
#pod
#pod =item * min_adjust_timeout => I<ufloat> (default: 5)
#pod
#pod Minimum timeout value, in seconds.
#pod
#pod This value bypasses any C<max_actual_duration> checks, so the total time spent on
#pod sleeping and attempts may end up exceeding that value by a small amount (up to
#pod C<max_actual_duration + min_adjust_timeout>).  In this case, future failures will return
#pod a delay of C<-1> as expected.
#pod
#pod =item * timeout_jitter_factor => I<float> (default: 0.1)
#pod
#pod How much randomness to add to the adjustable timeout.
#pod
#pod Delay jitter may not be enough to desynchronize two processes that are consistently
#pod timing out on the same problem.  In those cases, the delay will usually be zero and won't
#pod have any sort of jitter to solve the problem itself.  A jitter factor against the timeout
#pod will ensure simultaneous attempts have slightly different timeout windows.
#pod
#pod =back
#pod
#pod =head1 METHODS
#pod
#pod =head2 success
#pod
#pod     my ($delay, $timeout) = $retry_algo->success([ $timestamp ]);
#pod
#pod Log a successful attempt.  If not specified, C<$timestamp> defaults to current time.
#pod Unlike the L<base class|Algorithm::Backoff>, this method will return a list containing
#pod both the L<suggested delay|/delay> and the L<suggested timeout|/timeout> for the next
#pod attempt.
#pod
#pod =head2 failure
#pod
#pod     my ($delay, $timeout) = $retry_algo->failure([ $timestamp ]);
#pod
#pod Log a failed attempt.  If not specified, C<$timestamp> defaults to current time.
#pod Unlike the L<base class|Algorithm::Backoff>, this method will return a list containing
#pod both the L<suggested delay|/delay> and the L<suggested timeout|/timeout> for the next
#pod attempt.
#pod
#pod =cut

sub failure {
    my ($self, $timestamp) = @_;
    $timestamp //= time;

    my ($delay, $timeout) = $self->SUPER::failure($timestamp);

    # Fix certain values if the check failed max duration/attempts checks
    $timeout //= $self->timeout;
    if ($delay == -1) {
        $self->{_attempts}++;
        $self->{_last_timestamp} = $timestamp;
    }

    return ($delay, $timeout);
}

#pod =head2 delay
#pod
#pod     my $delay = $retry_algo->delay;
#pod
#pod Returns the last suggested delay, in seconds.
#pod
#pod The delay will return C<-1> to suggest that the process should give up and fail, if
#pod C<max_attempts> or C<max_actual_duration> have been reached.
#pod
#pod =cut

sub delay {
    my $self = shift;
    return $self->{_prev_delay} // 0;
}

#pod =head2 timeout
#pod
#pod     my $timeout = $retry_algo->delay;
#pod
#pod Returns the last suggested timeout, in seconds.  If no attempts have been logged,
#pod it will suggest an initial timeout to start with.
#pod
#pod This will be a floating-point number, so you may need to convert it to an integer if your
#pod timeout system doesn't support decimals.
#pod
#pod A timeout of C<-1> will be returned if C<max_actual_duration> was forcefully turned off.
#pod
#pod =cut

sub timeout {
    my $self = shift;

    my $last_timeout   = $self->{_last_timeout};
    my $min_time       = $self->{min_adjust_timeout};
    my $max_time       = $self->{max_actual_duration};
    my $timeout_factor = $self->{adjust_timeout_factor};

    return $last_timeout if defined $last_timeout;
    return -1 unless $max_time;

    my $timeout = $max_time * $timeout_factor;
    $timeout = $self->_add_timeout_jitter($timeout) if $self->{timeout_jitter_factor};
    $timeout = $min_time if $min_time > $timeout;
    return $timeout;
}

sub _set_last_timeout {
    my ($self, $delay, $timestamp) = @_;

    my $start_time     = $self->{_start_timestamp};
    my $min_time       = $self->{min_adjust_timeout};
    my $max_time       = $self->{max_actual_duration};
    my $timeout_factor = $self->{adjust_timeout_factor};
    return ($delay // 0, -1) unless defined $start_time && $max_time;

    $timestamp //= $self->{_last_timestamp} // $self->{_start_timestamp};

    # Calculate initial timeout
    my $actual_time_used = $timestamp - $start_time;
    my $actual_time_left = $max_time - $actual_time_used;
    my $timeout          = $actual_time_left * $timeout_factor;

    # Ensure the delay+timeout time isn't going to go over the limit
    $delay //= 0;
    my $max_delay = $actual_time_left * (1 - $timeout_factor);
    $delay = $max_delay if $delay > $max_delay;

lib/Algorithm/Backoff/RetryTimeouts.pm  view on Meta::CPAN

    $retry_algo says to not wait (since the attempt already used up the delay), and use
    a timeout of 11.7s

    4th attempt succeeds

=head1 CONSTRUCTOR

The L<"new"|Algorithm::Backoff::Exponential/new> constructor takes all of the base options
from L<Algorithm::Backoff::Exponential>. Some of the defaults are changed (also shown in
the L</SYNOPSIS> above), but otherwise function the same way.

=over

=item * L<max_attempts|Algorithm::Backoff::Exponential/new> => I<uint> (default: 8)

=item * L<max_actual_duration|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: 50)

=item * L<jitter_factor|Algorithm::Backoff::Exponential/new> => I<float> (default: 0.1)

=item * L<initial_delay|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: C<sqrt(2)>)

=item * L<exponent_base|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: C<sqrt(2)>)

=item * L<delay_on_success|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: 0)

=item * L<min_delay|Algorithm::Backoff::Exponential/new> => I<ufloat> (default: 0)

=item * L<max_delay|Algorithm::Backoff::Exponential/new> => I<ufloat>

=item * L<consider_actual_delay|Algorithm::Backoff::Exponential/new> => I<bool> (default: 1)

=back

The following new options are added in this module:

=over

=item * adjust_timeout_factor => I<ufloat> (default: 0.5)

How much of the remaining time to use for the next attempt's timeout, as a
factor between 0 and 1.

In order to prevent a single attempt from using up all of the remaining time, an
adjustable timeout will force the attempt to only use a portion of the time.  By default,
only 50% of the remaining time will be set as the next timeout value.

=item * min_adjust_timeout => I<ufloat> (default: 5)

Minimum timeout value, in seconds.

This value bypasses any C<max_actual_duration> checks, so the total time spent on
sleeping and attempts may end up exceeding that value by a small amount (up to
C<max_actual_duration + min_adjust_timeout>).  In this case, future failures will return
a delay of C<-1> as expected.

=item * timeout_jitter_factor => I<float> (default: 0.1)

How much randomness to add to the adjustable timeout.

Delay jitter may not be enough to desynchronize two processes that are consistently
timing out on the same problem.  In those cases, the delay will usually be zero and won't
have any sort of jitter to solve the problem itself.  A jitter factor against the timeout
will ensure simultaneous attempts have slightly different timeout windows.

=back

=head1 METHODS

=head2 success

    my ($delay, $timeout) = $retry_algo->success([ $timestamp ]);

Log a successful attempt.  If not specified, C<$timestamp> defaults to current time.
Unlike the L<base class|Algorithm::Backoff>, this method will return a list containing
both the L<suggested delay|/delay> and the L<suggested timeout|/timeout> for the next
attempt.

=head2 failure

    my ($delay, $timeout) = $retry_algo->failure([ $timestamp ]);

Log a failed attempt.  If not specified, C<$timestamp> defaults to current time.
Unlike the L<base class|Algorithm::Backoff>, this method will return a list containing
both the L<suggested delay|/delay> and the L<suggested timeout|/timeout> for the next
attempt.

=head2 delay

    my $delay = $retry_algo->delay;

Returns the last suggested delay, in seconds.

The delay will return C<-1> to suggest that the process should give up and fail, if
C<max_attempts> or C<max_actual_duration> have been reached.

=head2 timeout

    my $timeout = $retry_algo->delay;

Returns the last suggested timeout, in seconds.  If no attempts have been logged,
it will suggest an initial timeout to start with.

This will be a floating-point number, so you may need to convert it to an integer if your
timeout system doesn't support decimals.

A timeout of C<-1> will be returned if C<max_actual_duration> was forcefully turned off.

=head1 SEE ALSO

L<Algorithm::Backoff> - Base distro for this module

=head1 AUTHOR

Grant Street Group <developers@grantstreet.com>

=head1 COPYRIGHT AND LICENSE

This software is Copyright (c) 2020 - 2021 by Grant Street Group.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

=cut