Flask app on uwsgi/nginx - unix socket file is not created on booting

Question

I'm trying to use Flask app on uwsgi/nginx.

Following http://uwsgi-docs.readthedocs.org/en/latest/tutorials/Django_and_nginx.html and http://www.markjberger.com/flask-with-virtualenv-uwsgi-nginx/, I could make wiki.ini file,

[uwsgi]
vhost = true
socket = /tmp/flask_app.sock
venv = /home/ubuntu/webapp/flask/hello/.env
chdir = /home/ubuntu/webapp/flask/hello
module = flaskapp
callable = app
chmod-socket = 666

I checked the wiki.ini file works fine with uwsgi --ini wiki.ini.

Then, I tried to start the Flask app when booting.

From sudo update-rc.d uwsgi enable, I could start the uwsgi service in booting time, and copied the wiki.ini file in /etc/uwsgi/apps-enabled directory.

This is the conf file for nginx.

server {
    listen       80;
    server_name wiki.example.com;
    access_log  /var/log/nginx/uwsgi_access.log;
    error_log /var/log/nginx/uwsgi_error.log;

    location / { try_files $uri @riki; }
    location @riki {
        include uwsgi_params;
        uwsgi_pass unix:/tmp/flask_app.sock;
    }

    error_page  404              /404.html;
}

However, when I rebooted my ubuntu server, the Flask app isn't working. I checked the error log to find this error message.

2015/11/07 17:48:17 [crit] 1055#0: *1 connect() to 
unix:/tmp/flask_app.sock failed (2: No such file or directory) 
while connecting to upstream, client: 68.203.30.28, server: wiki.example.com,

I created the /tmp/flask_app.sock file and run chown -R www-data:www-data /tmp/flask_app.sock to make the application working.

> touch /tmp/flask_app.sock
> sudo chown www-data:www-data /tmp/flask_app.sock 
> sudo service uwsgi restart
> sudo service nginx restart

However, I had another connection refuse error.

2015/11/07 17:50:38 [error] 1055#0: *4 connect() to 
unix:/tmp/flask_app.sock failed (111: Connection refused) while 
connecting to upstream, client: 68.203.30.28, 
server: wiki.example.com, request: "GET / HTTP/1.1", 
upstream: "uwsgi://unix:/tmp/flask_app.sock:", host: "wiki.example.com"

What might be wrong? How to teach uwsgi to create the unix domain socket? Also, how to make the connection work? I use ubuntu 14.04.

EDIT

Removing the /tmp/flask_app.sock and run uwsgi --ini /etc/uwsgi/apps-enabled/wiki.ini makes the app working fine.

Answer 1

The main issue seems to be from the uwsgi service; it just doesn't work.

I found another way to start uwsgi at startup: upstart and uwsgi --emperor from http://uwsgi-docs.readthedocs.org/en/latest/Upstart.html and http://upstart.ubuntu.com

The process is just make a flask.conf file in /etc/init directory. uwsgi --emperor controls all the ini files in the uwsgi directory.

# simple uWSGI script
# http://uwsgi-docs.readthedocs.org/en/latest/Upstart.html

description "uwsgi tiny instance"
start on runlevel [2345]
stop on runlevel [06]

respawn

exec uwsgi --emperor /etc/uwsgi/apps-enabled

I also had to sudo update-rc.d uwsgi disable so that uwsgi service should be disabled.

I also found this site http://flaviusim.com/blog/Deploying-Flask-with-nginx-uWSGI-and-Supervisor/ for invoking uswgi at startup, but I didn't test it.