uwsgi error: bind(): No such file or directory [core/socket.c line 230]

Problem:

Sometimes, sites running on uwsgi and nginx cannot find socket file due to suddent restart of server. The most common error from /var/log/nginx/error.log in this case is:

bind(): No such file or directory [core/socket.c line 230]

Content of Nginx config file:

Support, content of /etc/nginx/sites-enabled/demo_app.ini is:

server {
    listen 80;
    server_name www.example.com;
    return 301 https://example.com$request_uri;
}

server {

    listen 80 default_server;
    server_name example.com;

    location = /favicon.ico { access_log off; log_not_found off; }

    location /static/ {
        alias /home/ubuntu/app/demo_app/static/;
            autoindex off;

            location ~* \.(eot|ttf|woff|woff2)$ {
            add_header 'Access-Control-Allow-Origin' '*';
        }
    }

    location /media/ {
        alias /home/ubuntu/app/demo_app/media/;
        autoindex off;
    }

    location / {
        add_header 'Access-Control-Allow-Origin' '*';

        include         uwsgi_params;
        uwsgi_pass      unix:/var/run/uwsgi/demo_app.sock;
    }
}

Content of uwsgi config file:

And, content of etc/uwsgi/sites/demo_app.ini file is:

project = demo_app
base    = /home/ubuntu/app

chdir   = %(base)/%(project)
home    = %(base)/venv
module  = conf.wsgi:application
env     = DJANGO_SETTINGS_MODULE=conf.settings

master  = true
processes = 5

socket = /var/run/uwsgi/%(project).sock
chmod-socket = 777
uid     = www-data
gid     = www-data

harakiri = 60
vacuum  = true
buffer-size = 32768

logger = file:/tmp/uwsgi.log
log-maxsize = 200000

Solution:

After a reboot socket file inside /var/run/uwsgi/ gets lost, because no folder exists with name uwsgi. That's why this folder is needed to be created.

mkdir /var/run/uwsgi

and

sudo chown -R www-data:www-data /var/run/uwsgi

Reference:
https://stackoverflow.com/questions/27791330/bind-no-such-file-or-directory-core-socket-c-line-230