连接上游时connect（）失败（111：拒绝连接）

Question

[error] 7697#7697: *100335 connect() failed (111: Connection refused) while connecting to upstream, client: XXX.XXX.XXX.XXX, server: v4.domain.com, request: "GET /socket.io/?__sails_io_sdk_version=0.13.8&__sails_io_sdk_platform=browser&__sails_io_sdk_language=javascript&EIO=3&transport=polling&t=Luvcibs HTTP/1.1", upstream: "http://127.0.0.1:1338/socket.io/?__sails_io_sdk_version=0.13.8&__sails_io_sdk_platform=browser&__sails_io_sdk_language=javascript&EIO=3&transport=polling&t=Luvcibs", host: "v4.domain.com", referrer: "http://v4.domain.com/?ct=t(Flash_Sals_Videotoolz_copy_05_12_29_2016)&mc_cid=404a630ab2&mc_eid=c44f7937fe"
[error] 7700#7700: *101735 connect() failed (111: Connection refused) while connecting to upstream, client: XX.XX.XX.XX, server: v4.domain.com, request: "GET /socket.io/?__sails_io_sdk_version=0.13.8&__sails_io_sdk_platform=browser&__sails_io_sdk_language=javascript&EIO=3&transport=polling&t=LuvciVy HTTP/1.1", upstream: "http://127.0.0.1:1338/socket.io/?__sails_io_sdk_version=0.13.8&__sails_io_sdk_platform=browser&__sails_io_sdk_language=javascript&EIO=3&transport=polling&t=LuvciVy", host: "v4.domain.com", referrer: "http://v4.domain.com/"

最近我在Ubuntu 16.04 VPS服务器上配置了我的sails js应用程序，它有nginx作为反向服务器。下面是我的网站nginx conf

网站运行良好，但突然发生网站中断并显示502坏网关。

尽我所能地尝试了几乎所有事情。

请帮我把它整理好。

server {
    listen 80 default_server;
    listen [::]:80 default_server;

    # SSL configuration
    #
    listen 443 ssl default_server;
    listen [::]:443 ssl default_server;
    #
    # Note: You should disable gzip for SSL traffic.
    # See: https://bugs.debian.org/773332
    #
    # Read up on ssl_ciphers to ensure a secure configuration.
    # See: https://bugs.debian.org/765782
    #
    # Self signed certs generated by the ssl-cert package
    # Don't use them in a production server!
    #
    # include snippets/snakeoil.conf;

    root /var/www/html/php;

    # Add index.php to the list if you are using PHP
    index index.html index.php index.htm index.nginx-debian.html;

    server_name domain.com www.domain.com;
    ssl_certificate /etc/letsencrypt/live/domain.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/domain.com/privkey.pem; # managed by Certbot
    ssl_dhparam /etc/ssl/certs/dhparam.pem;

    location / {
            # First attempt to serve request as file, then
            # as directory, then fall back to displaying a 404.
            #try_files $uri $uri/ =404;
            #try_files $uri $uri/ /index.php?q=$uri&$args;
            try_files $uri $uri/ /index.php?$args;
    }

    location ~ \.php$ {
    try_files not-existing-file @php;
}
location @php {
    #fastcgi_pass 127.0.0.1:9000;
        fastcgi_read_timeout 300;
        fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
    include snippets/fastcgi-php.conf;
}

    location ~* \.(css|js|png|jpg|jpeg|gif|ico)$ {
            expires 1d;
    }

    # deny access to .htaccess files, if Apache's document root
    # concurs with nginx's one
    #
    #location ~ /\.ht {
    #       deny all;
    #}


}


upstream sails_server {  
   server 127.0.0.1:1338; # fail_timeout=0;
   # keepalive 64;
}

server {  
   listen        80;
   listen        [::]:80;
   server_name   v4.domain.com;
   root /root/domain/;
   #Logging
   error_log /root/domain/log/error.log notice;

   location / {
       proxy_set_header  X-Real-IP         $remote_addr;
       proxy_set_header  Host              $host;
       proxy_http_version                  1.1;
       proxy_set_header  Connection        "";
       proxy_read_timeout                  300;
       proxy_pass                          http://sails_server;
       proxy_redirect                      off;
       # proxy_http_version                  1.1;
       proxy_set_header  Upgrade           $http_upgrade;
       # proxy_set_header  Connection        "";
       # proxy_set_header  Host              $host;
       proxy_set_header  X-Forwarded-For   $proxy_add_x_forwarded_for;
       proxy_set_header  X-Real-IP         $remote_addr;
       proxy_set_header  X-NginX-Proxy     true;
       # proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=one:10ms;
       # proxy_cache one;
       # proxy_cache_key sfs$request_uri$scheme;
       # proxy_pass_request_headers          on;
 }

 location /socket.io/ {
        proxy_pass http://sails_server/socket.io/;
        proxy_http_version 1.1;
        proxy_redirect off;
        proxy_set_header Host $host;
        proxy_set_header Port $server_port;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Nginx-Proxy true;
        proxy_pass_request_headers on;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_buffers 8 32k;
        proxy_buffer_size 64k;
   }
}

我的风帆应用程序的PM2配置文件位于

之下

{
  "apps": [
   {
       "name": "dj",
       "script"      : "./app.js",
       "watch": false,
       "ignore_watch" : ["node_modules", ".tmp"],
       "watch_options": {
         "followSymlinks": false
       },
       "env" : {
         "PORT": 1338,
         "NODE_ENV": "production"
       }
     }
   ]
 }