use Time::HiRes qw/ gettimeofday /;

sub log {
    my ( $self, $args ) = @_;

    my $data = {
        time    => join('.', ( gettimeofday )),
        pid     => $args->{'pid'},
        action  => $args->{'action'},
    };

    $self->write( $data );
}

##</code><code>##

mysql> select id, pid, action, from_unixtime(time) from queue_logger order by id;
+-------+-------+----------+----------------------------+
| id    | pid   | action   | from_unixtime(time)        |
+-------+-------+----------+----------------------------+
| 83640 | 15218 | finish   | 2016-05-06 12:38:49.834030 |
| 83642 | 15218 | sleep    | 2016-05-06 12:38:49.251690 | <- timestamped first, but inserted second!
| 83683 | 15218 | complete | 2016-05-06 12:39:19.707134 |
+-------+-------+----------+----------------------------+