Mojolicious, Mojo::Promise, DBI, and parallel requests

[eddy]

I am new in Mojolicious and playing around with this simple application to return rows from database. It seems to work fine for a single request, however when I use "xargs -n 1 -P 4" to run curl in parallel processes I start seeing "500 Internal Server Error" or "Empty reply from server".

The debug message in the log shows a number of "ORA-01002: fetch out of sequence" and "Worker 101864 has no heartbeat (50 seconds), restarting".

Really appreciate any guidance of what mistake that I made here.

use Mojolicious::Lite -signatures;
use Mojo::Promise;
use DBI;

my $dbh = DBI->connect(...);

app->config( hypnotoad => { listen => ['http://*:3000'], workers => 4, proxy => 1 });

helper select => sub {
    my $c = shift;
    my ($column1) = @_;

    my $query = <<~"END";
        SELECT *
        FROM mytable
        WHERE column1 = :column1
    END

    my $sth = $dbh->prepare($query) or do {
        $promise->reject("Failed to prepare SQL: " . $dbh->errstr);
        return;
    };
    $sth->bind_param(":column1", $column1);
    $sth->execute() or do {
        $promise->reject("Unable to execute SQL: " . $dbh->errstr);
        return;
    };

    # Fetch all rows from the result set
    my $data = $sth->fetchall_arrayref({});
    $sth->finish();

    return $data;
};

get '/foo/bar' => sub {
    my $c = shift;
    my $column1 = $c->param('column1');

    my $promise  = Mojo::Promise->new;
    Mojo::IOLoop->next_tick( sub {
        my $data = $c->select( $column1 );
        my @records = map { join('|', $_->{column1}, $_->{column2}) } $data->@*;
        my $ret_ref = JSON->new->utf8(1)->pretty(1)->encode( { 'MYRESULT' => \@records });

        $c->render(text => $ret_ref, format => 'json');
        # Return the data as pretty JSON
        $promise->resolve;
    });

    $promise->catch( sub {
        my ($err) = @_;
        $c->render(
            status => 500,
            json   => { zzzerror => $err }
        );
    });

    $promise->wait;
};

app->start;