AWS API Gateway Nginx Reverse Proxy

nginx.conf

# NOTE
#
#
# Use sed on the instance up to replace the INSTANCE_ID and DNS_RESOLVER with the following commands
#
####################################################################################################
# Fetch the private IP for resolving DNS dynamically in nginx
# We also need to escape the `.` from it for usage in later sed
#
# DNS_RESOLVER=`grep nameserver /etc/resolv.conf | cut -d " " -f2 | sed 's/\./\\./g'`
# INSTANCE_ID=`curl http://169.254.169.254/latest/meta-data/instance-id`
# sed -i.bak "s/DNS_RESOLVER/$DNS_RESOLVER/" /etc/nginx/nginx.conf
# sed -i.bak "s/INSTANCE_ID/$INSTANCE_ID/" /etc/nginx/nginx.conf
####################################################################################################


user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /var/run/nginx.pid;
include /usr/share/nginx/modules/*.conf;
events {
    worker_connections 1024;
}
http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for" "$http_host" "$served_host$prefix"';
    access_log  /var/log/nginx/access.log  main;
    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    proxy_ssl_server_name on; # critical for SNI support
    keepalive_timeout   65;
    types_hash_max_size 2048;
    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;
    include /etc/nginx/conf.d/*.conf;
    index   index.html index.htm;

    # Change mappings based on region and target API Gateway for Region
    map $http_host $served_host {
        api.example.com abcde12345.execute-api.us-east-2.amazonaws.com;
    }

    map $http_host $prefix {
        default "";
        api.example.com /prod;
        us-east-2-api.example.com /prod;
    }

    server {
        listen       80 default_server;
        listen       [::]:80 default_server;
        server_name  localhost;
        root         /usr/share/nginx/html;
        include /etc/nginx/default.d/*.conf;
        location /_proxy/healthcheck {
            return 200 '{"status": "ok", "message": "proxy is in service", "instance", "INSTANCE_ID"}';
            add_header Content-Type application/json;
        }
        error_page 404 /404.html;
            location = /40x.html {
        }
        error_page 500 502 503 504 /50x.html;
            location = /50x.html {
        }
        location / {
            resolver DNS_RESOLVER;
            proxy_pass https://$served_host$prefix$uri$is_args$args;
            proxy_set_header Host $served_host;
            proxy_buffering off;
            client_max_body_size 0;
            proxy_read_timeout 600s;
            proxy_redirect off;
        }
    }
}