nginx allow crawler to visit website

gistfile1.nginxconf

map $http_user_agent $is_bot {
    default       0;
    ~*(crawl|Googlebot|Slurp|spider|bingbot|yodaobot|youdaobot)$ 1;
}

set $should_redirect  1;
if ($is_bot) {
    set $should_redirect  0;
}

if ($ssl_protocol != "") {
    set $should_redirect 0;
}

if ($should_redirect = 1) {
    rewrite ^   https://$host$request_uri? permanent;
}