Nginx and uWSGI Flask app Connection Refused

Question

Trying to set up a Flask application with uWSGI and Nginx.

I keep getting a 502 Bad Gateway error (as far as I know this means uWSGI and Nginx can't communicate correctly)

This is the line that keeps showing up in my /var/log/nginx/error.log:

2016/07/29 17:07:12 [error] 24958#24958: *2 connect() to unix:/home/lit/howlit/how_lit_restapi.sock failed (111: Connection refused) while connecting to upstream, client: 

This is my project directory and it's permissions:

(env) root@digitalocean:/home/lit/howlit# ls -l total 24 drwx---r-x 6 lit www-data 4096 Jul 29 11:47 env -rwx---r-x 1 lit www-data 141 Jul 29 17:00 howlit.ini -rwx---r-x 1 lit www-data 1175 Jul 29 11:52 how_lit_restapi.py -rwx---r-x 1 lit www-data 1781 Jul 29 11:54 how_lit_restapi.pyc srwx---r-x 1 lit www-data 0 Jul 29 16:46 how_lit_restapi.sock -rwx---r-x 1 lit www-data 73 Jul 29 11:54 wsgi.py -rwx---r-x 1 lit www-data 218 Jul 29 11:54 wsgi.pyc 

This is my howlit.ini file:

(env) root@digitalocean:/home/lit/howlit# cat howlit.ini [uwsgi] module = wsgi:app master = true processes = 5 socket = how_lit_restapi.sock chmod-sock = 660 vaccum = true die-on-term = true 

this is my /etc/nginx/sites-available/how_lit file:

(env) root@digitalocean:/home/lit/howlit# cat /etc/nginx/sites-available/how_lit server { listen 80; server_name XXX.XX.XX.XXX; location / { include uwsgi_params; uwsgi_pass unix:/home/lit/howlit/how_lit_restapi.sock; } } 

*the xxxs are to protect my server IP; there is a real IP address there.

Here is the nginx conf file:

user lit; worker_processes auto; pid /run/nginx.pid; events { worker_connections 768; # multi_accept on; } http { ## # Basic Settings ## sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 65; types_hash_max_size 2048; # server_tokens off; # server_names_hash_bucket_size 64; # server_name_in_redirect off; include /etc/nginx/mime.types; default_type application/octet-stream; ## # SSL Settings ## ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE ssl_prefer_server_ciphers on; ## # Logging Settings ## access_log /var/log/nginx/access.log; error_log /var/log/nginx/error.log; ## # Gzip Settings ## gzip on; gzip_disable "msie6"; # gzip_vary on; # gzip_proxied any; # gzip_comp_level 6; # gzip_buffers 16 8k; # gzip_http_version 1.1; # gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript; ## # Virtual Host Configs ## include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } 

Permissions of directory with socket:

root@digitalocean:~# ls -l /home/lit/howlit/

total 24 drwx---r-x 6 lit www-data 4096 Jul 29 11:47 env -rwx---r-x 1 lit www-data 141 Jul 29 19:01 howlit.ini -rwx---r-x 1 lit www-data 1175 Jul 29 11:52 how_lit_restapi.py -rwx---r-x 1 lit www-data 1781 Jul 29 11:54 how_lit_restapi.pyc srwx---r-x 1 lit www-data 0 Jul 29 16:46 how_lit_restapi.sock -rwx---r-x 1 lit www-data 73 Jul 29 11:54 wsgi.py -rwx---r-x 1 lit www-data 218 Jul 29 11:54 wsgi.pyc 

I've tried changing permissions and the files alot. What is my problem here? Why is the connection being refused???

UPDATE:

So when I run my application manually:

root@digitalocean:/home/lit/howlit# python how_lit_restapi.py * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit) 

and I go to my ip address at:

XXX.XX.XX:5000 

my app shows up, so I know uwwsgi is running and serving. But the nginx hand off is not work.

Here is my how_lit.service file as well.

root@digitalocean:/home/lit/howlit# vim /etc/systemd/system/how_lit.service [Unit] Description=uWSGI instance to serve how lit rest api After=network.target [Service] User=lit Group=www-data WorkingDirectory=/home/lit/howlit/ Environment="PATH=/home/lit/howlit/env/bin" ExecStart=/home/lit/howlit/env/bin/uwsgi --ini howlit/howlit.ini [Install] WantedBy=multi-user.target 

Okay then now I think I have it. The how_lit service is failing.

Answer 1

I'd move towards specifying an 'upstream' where you set your server/socket and reference that in your virtual host, like:

upstream django { server unix:///var/run/whatever.sock; # for a file socket } server { listen 80 location / { uwsgi_pass django; } } 

You can use lsof to make sure things are writing to / reading from the socket.

Answer 2

Which user is running uwsgi? In your config file, you've specified:

chmod-sock = 660 

This means, the user in question and his group are able to read / write, all other users aren't able to do anything. Try changing it to

chmod-sock = 666 

and see how this goes.

A better alternative might be to put the uwsgi user and the one running nginx into the same group.

Edit: Does the socket exist at the path you've specified? If not, change the socket directive so that it uses a full / absolute path.

Answer 3

These are some of the troubleshooting steps you might need to perform -

1). Check the uwsgi logs, usually under /var/log/uwsig - look for errors and make sure the app you specified in your configuration as module = wsgi:app is loading.

2). Check for any permission issues. To make this easier, start uwsgi under the same user/group as nginx. You can add the line below to your uwsgi config -

 uid = www-data gid = www-data 

3). You might need to install uwsgi-plugin-python package and add plugins = python to your uwsgi config. I had cases where the app was not loading due to missing plugin.