title: how to setup nginx not to crash if grpc server`s hostname in upstream is not found
body: <p>nginx version: 1.13.10</p>
  
  <p>Config looks like this:</p>
  
  <pre><code>events {
  multi_accept        on;
  worker_connections  16384;
  use                 epoll;
  }
  http {
      log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
              '$status $body_bytes_sent "$http_referer" '
              '"$http_user_agent"';
      server {
              listen 80 http2;
  
              access_log /dev/stdout main;
  
              location /foo.test {
                      grpc_pass grpc://foo:8088;
              }
      }
  }
  </code></pre>
  
  <p>If the app is not started then nginx fails and stops:</p>
  
  <p>We don't need them all to be up but nginx fails otherwise. How to make nginx ignore failed upstreams?</p>
  
  <p>i have try this solution <a href="https://stackoverflow.com/a/32846603/6249187">Setup nginx not to crash if host in upstream is not found
  (not grpc )</a>  </p>
  
  <p>but it work for proxy_pass http proxy ,not work for grpc_pass.</p>
  
  <p>does anyone have some idea ?</p>