Nginx找不到主机

Question

在Nginx日志中，我发现：host not found in upstream "swagger" in /etc/nginx/conf.d/prod.conf

这是我的prod.conf文件：

server {

  listen 80;

  ...
  ...

  location /auth {
  proxy_pass        http://users:5000;
  proxy_http_version 1.1;
  proxy_redirect    default;
  proxy_set_header  Upgrade $http_upgrade;
  proxy_set_header  Connection "upgrade";
  proxy_set_header  Host $host;
  proxy_set_header  X-Real-IP $remote_addr;
  proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_set_header  X-Forwarded-Host $server_name;
}

location /swagger {
  proxy_pass        http://swagger:8080;
  proxy_http_version 1.1;
  proxy_redirect    default;
  proxy_set_header  Upgrade $http_upgrade;
  proxy_set_header  Connection "upgrade";
  proxy_set_header  Host $host;
  proxy_set_header  X-Real-IP $remote_addr;
  proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_set_header  X-Forwarded-Host $server_name;
}
}

为什么Nginx无法看到已定义的路由swagger？ （这只是一个“填充”文本，用于传递问题的SO的最小字符限制）