Add Deadlock Retries

[theory]

Should work for serialization failures, too. See this blog post for details and discussion (especially the comments from Kevin Grittner).

[Perlover]

+1
I very want to have fixup mode for deadlocks in InnoDB! :)

[matthewlenz]

How terrible is this (uses Try::Tiny::Retry)? The only obvious issue I see is that your code already reattempts connections for some of those exceptions so the total number of tries will be more.

sub retry_txn {
    my ($self, $code, $rethrow) = @_;

    my $dbc = $self->get_dbc();

    return retry {
        $dbc->txn(fixup => $code);
    } delay {
        return if $_[0] >= 10;
        sleep 0.5*$_[0];
    } on_retry {
        warn "Retrying transaction.";
    } retry_if {
        my $err = $_;
        $err = $err->error
            if (eval { $err->isa('DBIx::Connector::RollbackError') });
        $err =~ /deadlock|lost connection|gone away|can't connect/i;
    } catch {
        if ($rethrow) {
            my $err = $_;
            $err = $err->error
                if (eval { $err->isa('DBIx::Connector::RollbackError') });
            die $err; 
        }
    };
}

Usage would be something like:

$app->retry_txn(sub {
    $app->some_sql_actions();
});

or

try {
    $app->retry_txn(sub {
        $app->some_sql_actions();
    }, 1);
} catch {
    warn 'oh Snap!';
};