Create a .ebextentions folder in the root of your project.

Create a file 01_nginx.config under the .ebextentions folder with the following content and redeploy:

files:
/etc/nginx/conf.d/proxy.conf:
content: |
client_max_body_size 500M;
server_names_hash_bucket_size 128;

upstream backend {
server unix:///var/run/puma/my_app.sock;
}

server {
listen 80;

access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;

server_name localhost;

large_client_header_buffers 8 32k;

location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_set_header X-NginX-Proxy true;

proxy_buffers 8 32k;
proxy_buffer_size 64k;

proxy_pass http://backend;
proxy_redirect off;

location /assets {
root /var/app/current/public;
}

location /vendor {
root /var/app/current/public;
}

# enables WS support
location /cable {
proxy_pass http://backend;
proxy_http_version 1.1;
proxy_set_header Upgrade "websocket";
proxy_set_header Connection "Upgrade";
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
}

container_commands:
01restart_nginx:
command: "service nginx restart"