The simplest configuration for load balancing with nginx

default.conf

http {
    upstream myapp1 {
        server srv1.example.com;
        server srv2.example.com;
        server srv3.example.com;
    }

    server {
        listen 80;

        location / {
            proxy_pass http://myapp1;
        }
    }
}

phpfpm.conf

server {
    listen         80 default_server;
    listen [::]:80 default_server;
    server_name    omg.test;
    root           /var/www/html/public_html/public;
    index          index.php;

    client_max_body_size 10M;
    client_body_buffer_size 10M;

    location ~* \.php$ {
     if (!-f $document_root$fastcgi_script_name) {
        return 404;
     }    
     fastcgi_pass omg_upstream;
     fastcgi_index index.php;

     fastcgi_param   SCRIPT_FILENAME    $document_root$fastcgi_script_name;
     fastcgi_param   SCRIPT_NAME        $fastcgi_script_name;

     fastcgi_split_path_info ^(.+\.php)(/.+)$;

     include         fastcgi_params;
   }

   location / {
      try_files $uri $uri/ /index.php?$query_string;
   }

   ##
      # `gzip` Settings
      #
      #
      gzip on;
      gzip_disable "msie6";

      gzip_vary on;
      gzip_proxied any;
      gzip_comp_level 9;
      gzip_buffers 16 8k;
      gzip_http_version 1.1;
      gzip_min_length 0;
      gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript application/vnd.ms-fontobject application/x-font-ttf font/opentype image/svg+xml image/x-icon;
}

upstream omg_upstream {
   server services_omg_phpfpm_1:9000;
#   server services_omg_phpfpm_2:9000;
#   server services_omg_phpfpm_3:9000;
#   server services_omg_phpfpm_4:9000;
#   server services_omg_phpfpm_5:9000;
}

socket-io.conf

http {
  server {
    listen 3000;
    server_name io.yourhost.com;

    location / {
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header Host $host;

      proxy_pass http://nodes;

      # enable WebSockets
      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "upgrade";
    }
  }

  upstream nodes {
    # enable sticky session based on IP
    ip_hash;

    server app01:3000;
    server app02:3000;
    server app03:3000;
  }
}