nginx: how to not exit if "host not found in upstream"?

We have several rails apps under common domain in Docker, and we use nginx to direct requests to specific apps. our_dev_server.com/foo # proxies to foo app our_dev_server.com/bar # proxies to bar Config looks like this: upstream foo { server foo:3000; } upstream bar { server bar:3000; } # and about 10 more... server { listen *:80 default_server; server_name our_dev_server.com; location /foo { # this is specific to asset management in rails dev rewrite ^/foo/assets(/.*)$ /assets/$1 break; rewrite ^/foo(/.*)$ /foo/$1 break; proxy_pass http://foo; } location /bar { rewrite ^/bar/assets(/.*)$ /assets/$1 break; rewrite ^/bar(/.*)$ /bar/$1 break; proxy_pass http://bar; } # and about 10 more... } If one of these apps is not started then nginx fails and stops: host not found in upstream "bar:3000" in /etc/nginx/conf.d/nginx.conf:6 We don't need them all to be up but nginx fails otherwise. How to make nginx ignore failed upstreams?