python - Flask with Gunicorn on nginx 502 bad gateway 错误

Question

经过一些 ubuntu 16.04 升级和应用程序代码修改后，我之前在gunicorn 和 nginx 网站上运行的 Flask 现在出现 502 bad gateway 错误。

myapp.conf:

upstream app_server_wsgiapp {
  server localhost:8000 fail_timeout=0;
}

server {
  listen 80;
  server_name www.myserver.com;

  access_log   /var/log/nginx/www.myapp.access.log;
  error_log   /var/log/nginx/www.myapp.error.log info;
  keepalive_timeout    5;

  location /static {
    autoindex on;
    alias /myapp/static;
  }

  location / {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;
    if (!-f $request_filename) {
      proxy_pass http://app_server_wsgiapp;
      break; 
    }
    client_max_body_size 2097152;
    #to get around upstream sent too big header while reading response header from upstream error
    proxy_buffer_size          128k;
    proxy_buffers              4 256k;
    proxy_busy_buffers_size    256k;
  }

  # this section allows Nginx to reverse proxy for websockets
  location /socket.io {
    proxy_pass http://app_server_wsgiapp/socket.io;
    proxy_redirect off;
    proxy_buffering 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;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";
  } 
}

/var/log/nginx/myapp.error.log

2017/06/11 06:42:52 [error] 31054#31054: *1 connect() failed (111: Connection refused) while connecting to upstream, client: clientip, server: www.myserver.com, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8000/", host: "www.myapp.com"

从我的应用程序日志文件中，我注意到 Flask 已经启动了一部分，然后在连续的失败/重新启动循环中重新启动。

我有什么想法可以调试可能导致此问题的原因吗？

Answer 1

看起来问题是由 Flask 应用程序运行错误引起的。您能尝试以交互方式运行该应用程序吗？以守护进程方式使用相同的参数和环境设置，检查服务是否可以正确启动？