Rails + Nginx + SSL - 允许某些路由不使用 SSL

Question

我有一个由 nginx 提供服务的 rails 应用。我已使用以下配置在所有路由上启用了 ssl：

server {
  listen      [::]:80;
  listen      80;
  server_name domain.com;
  access_log  /var/log/nginx/domain-access.log;
  error_log   /var/log/nginx/domain-error.log;
  return 301 https://$host:443$request_uri;
}

server {
  listen      [::]:443 ssl spdy;
  listen      443 ssl spdy;
  server_name domain.com;
  access_log  /var/log/nginx/domain-access.log;
  error_log   /var/log/nginx/domain-error.log;
ssl_certificate     /home/dokku/domain/tls/server.crt;
ssl_certificate_key /home/dokku/domain/tls/server.key;

  keepalive_timeout   70;
  add_header          Alternate-Protocol  443:npn-spdy/2;
  location    / {

    gzip on;
    gzip_min_length  1100;
    gzip_buffers  4 32k;
    gzip_types    text/css text/javascript text/xml text/plain text/x-component application/javascript application/x-javascript application/json application/xml  application/rss+xm$
    gzip_vary on;
    gzip_comp_level  6;

    proxy_pass  http://domain;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection upgrade;
    proxy_set_header Host $http_host;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-For $remote_addr;
    proxy_set_header X-Forwarded-Port $server_port;
    proxy_set_header X-Request-Start $msec;
  }
  include /home/dokku/domain/nginx.conf.d/*.conf;
}

我想允许（但不强制）某些路线上的非 SSL 连接，如下所示：

domain.com => enforce ssl
domain.com/l/* => allow non-ssl
domain.com/* => enforce ssl

根据上述配置，我该如何实现这一点？

谢谢！