502 Bad Gateway from relocated instance on AWS EC2

Question

I tried to move some instance from tokio region (which by the way, it's working normally) to sao paulo region, then I followed this basic steps to perform but when I launch the instance from the generated AMI and turn on, it shows me "502 Bad Gateway" message in browser.

The principal components on this relocated server are: nginx, uwsgi, django, supervisor, new relic.

All configurations are the same for this relocated server, so I restarted all services, it seems that nginx is working well however it has a detail to apply the next config which is config file of my site:

nginx/sites-available/mysite:

server {
    listen 80;
    server_name mysite.com;

    access_log /var/log/nginx/site_access.log;
    error_log /var/log/nginx/site_error.log;

    location /static {
        alias  /home/ubuntu/apps/site/static/;
    }

    location /media/  {
        alias /home/ubuntu/apps/site/media/;
    }

    location / {
    client_max_body_size 400M;
    proxy_read_timeout 120;
        proxy_connect_timeout 120;
    proxy_set_header Host $http_host; 
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header Client-IP $remote_addr;
        proxy_set_header X-Forwarded-For $remote_addr;
        proxy_pass http://127.0.0.1:8888;
    proxy_buffering off;
    }
}

To be honest, I expected it operate normally since http://127.0.0.1:8888 is working but I don't understand the reason why nginx conexion is broken, I need some help so that I can research a little more. what else am I forgetting?

UPDATE:

Well ... By the @Michael - sqlbot's suggestion I checked log files, according to this file:

/var/log/nginx/site_error.log

2015/04/06 15:34:31 [error] 832#0: *12 connect() failed (111: Connection refused)
while connecting to upstream, client:
190.233.157.2, server: mysite.com, request: "GET /favicon.ico HTTP/1.1", upstream:
"http://127.0.0.1:8888/favicon.ico", host: "54.207.136.99"

By what I'm going to verify the conexion again and it's what shows me:

$ ping 127.0.0.1

PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_req=1 ttl=64 time=0.035 ms
64 bytes from 127.0.0.1: icmp_req=2 ttl=64 time=0.028 ms
64 bytes from 127.0.0.1: icmp_req=3 ttl=64 time=0.028 ms
64 bytes from 127.0.0.1: icmp_req=4 ttl=64 time=0.026 ms
--- 127.0.0.1 ping statistics ---

And then I tried it with curl and after about 30 seconds, it prints the following:

$ curl 127.0.0.1:8888

curl: (56) Recv failure: Connection reset by peer

I'm having this strange error, what does it mean really ?

UPDATE 2:

There are config file of mysite on uwsgi and their logs file, however it's the same kind of messages of server on tokio (which is working normally), so I discard that this was a problem of uwsgi:

/etc/uwsgi/apps-enabled/mysite.ini

[uwsgi]
vhost = true
plugins = python
socket = /tmp/mysite.sock
master = true
enable-threads = true
processes = 2
wsgi-file = /home/ubuntu/apps/mysite/mysite/wsgi.py
virtualenv = /home/ubuntu/.venv/mysite
chdir = /home/ubuntu/apps/mysite
touch-reload = /home/ubuntu/apps/mysite/reload

/var/log/uwsgi/app/mysite.log

[uWSGI] getting INI configuration from /usr/share/uwsgi/conf/default.ini
[uWSGI] getting INI configuration from /etc/uwsgi/apps-enabled/mysite.ini
Sun Apr 12 18:29:55 2015 - *** Starting uWSGI 1.0.3-debian (64bit) on [Sun Apr 12 18:29:55 2015] ***
Sun Apr 12 18:29:55 2015 - compiled with version: 4.6.3 on 17 July 2012 02:26:54
Sun Apr 12 18:29:55 2015 - current working directory: /
Sun Apr 12 18:29:55 2015 - writing pidfile to /run/uwsgi/app/mysite/pid
Sun Apr 12 18:29:55 2015 - detected binary path: /usr/bin/uwsgi-core
Sun Apr 12 18:29:55 2015 - setgid() to 33
Sun Apr 12 18:29:55 2015 - setuid() to 33
Sun Apr 12 18:29:55 2015 - your memory page size is 4096 bytes
Sun Apr 12 18:29:55 2015 - VirtualHosting mode enabled.
Sun Apr 12 18:29:55 2015 - uwsgi socket 0 bound to UNIX address /run/uwsgi/app/mysite/socket fd 5
Sun Apr 12 18:29:55 2015 - uwsgi socket 1 bound to UNIX address /tmp/mysite.sock fd 6
Sun Apr 12 18:29:55 2015 - Python version: 2.7.3 (default, Aug  1 2012, 05:25:23)  [GCC 4.6.3]
Sun Apr 12 18:29:55 2015 - Set PythonHome to /home/ubuntu/.venv/mysite
Sun Apr 12 18:29:55 2015 - Python main interpreter initialized at 0x916120
Sun Apr 12 18:29:55 2015 - threads support enabled
Sun Apr 12 18:29:55 2015 - your server socket listen backlog is limited to 100 connections
Sun Apr 12 18:29:55 2015 - *** Operational MODE: preforking ***
Sun Apr 12 18:29:57 2015 - WSGI application 0 (mountpoint='') ready on interpreter 0x916120 pid: 1137 (default app)
Sun Apr 12 18:29:57 2015 - *** uWSGI is running in multiple interpreter mode ***
Sun Apr 12 18:29:57 2015 - spawned uWSGI master process (pid: 1137)
Sun Apr 12 18:29:57 2015 - spawned uWSGI worker 1 (pid: 1236, cores: 1)
Sun Apr 12 18:29:57 2015 - spawned uWSGI worker 2 (pid: 1237, cores: 1)
Sun Apr 12 18:29:57 2015 - unable to stat() /home/ubuntu/apps/mysite/reload, reload will be triggered as soon as the file is created

UPDATE 3:

I typed netstat -nap -p | grep 8888 and it shows me:

tcp        0      0 127.0.0.1:8888          0.0.0.0:*               LISTEN      7550/python

then I typed ps aux | grep 7550 and ...

ubuntu    7550  2.4  0.4  65752 15568 ?        S    21:44   0:00 /home/ubuntu/.venv/mysite/bin/python /home/ubuntu/.venv/mysite/bin/gunicorn_django -w 3 --user=ubuntu --group=ubuntu --log-level=debug --timeout 120 --log-file=/var/log/gunicorn/mysite.log -b 127.0.0.1:8888
ubuntu    7585  0.0  0.0   8104   924 pts/1    S+   21:44   0:00 grep --color=auto 7550

Well, I checked with cat /var/log/gunicorn/mysite.log and I got this:

Traceback (most recent call last):
  File "/home/ubuntu/.venv/mysite/bin/gunicorn_django", line 8, in <module>
    load_entry_point('gunicorn==0.14.6', 'console_scripts', 'gunicorn_django')()
  File "/home/ubuntu/.venv/mysite/local/lib/python2.7/site-packages/gunicorn/app/djangoapp.py", line 132, in run
    DjangoApplication("%prog [OPTIONS] [SETTINGS_PATH]").run()
  File "/home/ubuntu/.venv/mysite/local/lib/python2.7/site-packages/gunicorn/app/base.py", line 124, in run
    Arbiter(self).run()
  File "/home/ubuntu/.venv/mysite/local/lib/python2.7/site-packages/gunicorn/arbiter.py", line 185, in run
    self.halt(reason=inst.reason, exit_status=inst.exit_status)
  File "/home/ubuntu/.venv/mysite/local/lib/python2.7/site-packages/gunicorn/arbiter.py", line 280, in halt
    self.stop()
  File "/home/ubuntu/.venv/mysite/local/lib/python2.7/site-packages/gunicorn/arbiter.py", line 328, in stop
    self.reap_workers()
  File "/home/ubuntu/.venv/mysite/local/lib/python2.7/site-packages/gunicorn/arbiter.py", line 419, in reap_workers
    raise HaltServer(reason, self.WORKER_BOOT_ERROR)
gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>
2015-04-12 21:44:36 [7550] [INFO] Starting gunicorn 0.14.6
2015-04-12 21:44:36 [7550] [DEBUG] Arbiter booted
2015-04-12 21:44:36 [7550] [INFO] Listening at: http://127.0.0.1:8888 (7550)
2015-04-12 21:44:36 [7550] [INFO] Using worker: sync
2015-04-12 21:44:36 [7558] [INFO] Booting worker with pid: 7558
2015-04-12 21:44:36 [7559] [INFO] Booting worker with pid: 7559
2015-04-12 21:44:36 [7560] [INFO] Booting worker with pid: 7560
Production environment is up!
Production environment is up!
Production environment is up!

Well ... Gunicorn seems to be failing (it's inside virtualenv), so I checked the exucution on debug mode:

gunicorn mysite.wsgi:application --preload --debug --log-level debug

2015-04-12 22:32:42 [9085] [DEBUG] Current configuration:
2015-04-12 22:32:42 [9085] [DEBUG]   access_log_format: "%(h)s %(l)s %(u)s %(t)s "%(r)s" %(s)s %(b)s "%(f)s" "%(a)s"
2015-04-12 22:32:42 [9085] [DEBUG]   accesslog: None
2015-04-12 22:32:42 [9085] [DEBUG]   backlog: 2048
2015-04-12 22:32:42 [9085] [DEBUG]   bind: 127.0.0.1:8000
2015-04-12 22:32:42 [9085] [DEBUG]   check_config: False
2015-04-12 22:32:42 [9085] [DEBUG]   config: None
2015-04-12 22:32:42 [9085] [DEBUG]   daemon: False
2015-04-12 22:32:42 [9085] [DEBUG]   debug: True
2015-04-12 22:32:42 [9085] [DEBUG]   default_proc_name: mysite.wsgi:application
2015-04-12 22:32:42 [9085] [DEBUG]   django_settings: None
2015-04-12 22:32:42 [9085] [DEBUG]   errorlog: -
2015-04-12 22:32:42 [9085] [DEBUG]   graceful_timeout: 30
2015-04-12 22:32:42 [9085] [DEBUG]   group: 1000
2015-04-12 22:32:42 [9085] [DEBUG]   keepalive: 2
2015-04-12 22:32:42 [9085] [DEBUG]   limit_request_field_size: 8190
2015-04-12 22:32:42 [9085] [DEBUG]   limit_request_fields: 100
2015-04-12 22:32:42 [9085] [DEBUG]   limit_request_line: 4094
2015-04-12 22:32:42 [9085] [DEBUG]   logconfig: None
2015-04-12 22:32:42 [9085] [DEBUG]   logger_class: simple
2015-04-12 22:32:42 [9085] [DEBUG]   loglevel: debug
2015-04-12 22:32:42 [9085] [DEBUG]   max_requests: 0
2015-04-12 22:32:42 [9085] [DEBUG]   on_reload: <function on_reload at 0x7f6f421e9320>
2015-04-12 22:32:42 [9085] [DEBUG]   on_starting: <function on_starting at 0x7f6f421e91b8>
2015-04-12 22:32:42 [9085] [DEBUG]   pidfile: None
2015-04-12 22:32:42 [9085] [DEBUG]   post_fork: <function post_fork at 0x7f6f421e9758>
2015-04-12 22:32:42 [9085] [DEBUG]   post_request: <function post_request at 0x7f6f421e9b18>
2015-04-12 22:32:42 [9085] [DEBUG]   pre_exec: <function pre_exec at 0x7f6f421e98c0>
2015-04-12 22:32:42 [9085] [DEBUG]   pre_fork: <function pre_fork at 0x7f6f421e95f0>
2015-04-12 22:32:42 [9085] [DEBUG]   pre_request: <function pre_request at 0x7f6f421e9a28>
2015-04-12 22:32:42 [9085] [DEBUG]   preload_app: True
2015-04-12 22:32:42 [9085] [DEBUG]   proc_name: None
2015-04-12 22:32:42 [9085] [DEBUG]   pythonpath: None
2015-04-12 22:32:42 [9085] [DEBUG]   secure_scheme_headers: {'X-FORWARDED-PROTOCOL': 'ssl', 'X-FORWARDED-SSL': 'on'}
2015-04-12 22:32:42 [9085] [DEBUG]   spew: False
2015-04-12 22:32:42 [9085] [DEBUG]   timeout: 30
2015-04-12 22:32:42 [9085] [DEBUG]   tmp_upload_dir: None
2015-04-12 22:32:42 [9085] [DEBUG]   umask: 0
2015-04-12 22:32:42 [9085] [DEBUG]   user: 1000
2015-04-12 22:32:42 [9085] [DEBUG]   when_ready: <function when_ready at 0x7f6f421e9488>
2015-04-12 22:32:42 [9085] [DEBUG]   worker_class: sync
2015-04-12 22:32:42 [9085] [DEBUG]   worker_connections: 1000
2015-04-12 22:32:42 [9085] [DEBUG]   worker_exit: <function worker_exit at 0x7f6f421e9c80>
2015-04-12 22:32:42 [9085] [DEBUG]   workers: 1
2015-04-12 22:32:42 [9085] [DEBUG]   x_forwarded_for_header: X-FORWARDED-FOR
2015-04-12 22:32:42 [9085] [WARNING] debug mode: app isn't preloaded.
2015-04-12 22:32:42 [9085] [INFO] Starting gunicorn 0.14.6
2015-04-12 22:32:42 [9085] [DEBUG] Arbiter booted
2015-04-12 22:32:42 [9085] [INFO] Listening at: http://127.0.0.1:8000 (9085)
2015-04-12 22:32:42 [9085] [INFO] Using worker: sync
2015-04-12 22:32:42 [9088] [INFO] Booting worker with pid: 9088
^[[A^C2015-04-12 22:34:38 [9088] [INFO] Worker exiting (pid: 9088)
2015-04-12 22:34:38 [9085] [INFO] Handling signal: int
2015-04-12 22:34:38 [9085] [INFO] Shutting down: Master

I know there's a problem with gunicorn so far, it fails and restart itself and fails again, but these messages does not shows me a clear error ... is there another ideas ? I'm starting to feel very confunsed :S

Answer 1

Effectively ... Environment variables were the culprits (and me, for not realizing), they were not configured properly therefore Django crashes when Gunicorn tries to run it.

And I solved this problem by checking all environment vars and setup properly according to my instance EC2 ... thnks so much to @Serj Zaharchenko for the simple but powerful clue.