Docker Nginx stopped: [emerg] 1#1: host not found in upstream

Question

I am running docker-nginx on ECS server. My nginx service is suddenly stopped because the proxy_pass of one of the servers got unreachable. The error is as follows:

[emerg] 1#1: host not found in upstream "dev-example.io" in /etc/nginx/conf.d/default.conf:988 

My config file is as below:

 server {        listen      80;        server_name     test.com;        location / {           proxy_pass         http://dev-exapmle.io:5016/;           proxy_redirect     off;            ##proxy_set_header   Host             $host;           proxy_set_header   X-Real-IP        $remote_addr;           proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;            client_max_body_size       10m;           client_body_buffer_size    128k;            proxy_connect_timeout      90;           proxy_send_timeout         90;           proxy_read_timeout         90;            proxy_buffer_size          4k;           proxy_buffers              4 32k;           proxy_busy_buffers_size    64k;           proxy_temp_file_write_size 64k;        } }  server {    listen       80 default_server;    server_name  localhost;     #charset koi8-r;    #access_log  /var/log/nginx/log/host.access.log  main;     location / {       root   /usr/share/nginx/html;       index  index.html index.htm;    }     #error_page  404              /404.html;     # redirect server error pages to the static page /50x.html    #    error_page   500 502 503 504  /50x.html;    location = /50x.html {       root   /usr/share/nginx/html;    } } 

I have many servers in the config file, even if one server was down, I need to have running nginx. Is there any way to fix it?

Any suggestion to fix this issue would be appreciated.

Answer 1

Just adding a resolver did not resolve the issue in my case. But I was able to work around it by using a variable for the host. Also, I guess it makes more sense to use Docker's DNS at 127.0.0.11 (this is a fixed IP).

Example:

server {   listen 80;   server_name test.com;      location / {     resolver 127.0.0.11;     set $example dev-example.io:5016;     proxy_pass http://$example;   } } 

I found the variable workaround on this page.

Answer 2

Include to prevent Nginx from crashing if your site is down, include a resolver directive, as follows:

 server {        listen                80;        server_name           test.com;        location / {           resolver           8.8.8.8;           proxy_pass         http://dev-exapmle.io:5016/;           proxy_redirect     off;  ... 

WARNING! Using a public DNS create a security risk in your backend since your DNS requests can be spoofed. If this is an issue, you should point the resolver to a secure DNS server.