如何使用flask / uwsgi / nginx服务器管理内容和python代码？

Question

After running Flask for a few days as a live webserver, I learned this is not a smart thing to do: after some hours of inactivity the server died, even when I used the most simple setup (one page, no python code). Googling around I found out that Flask is not meant to be used as production server and a good practice is to combine it with eg Nginx and uWSGI. So I followed this guide and it seems to be running well. But now I have no clue how to restart, refresh or reload whatever it takes to publish te stuff I add to the content or to the python code. In stead of the Flask server, which reloads automatically after a file is saved (when in debug mode) I now have three engines running. Restarting nginx in terminal does not work, I've already tried that.

Please can somebody help this noob out?

TIA!!

uwsgi_conf.ini:

============================

[uwsgi]

chdir = /home/pi/sampleApp
module = sample_app:first_app

master = true
processes = 1
threads = 2

uid = www-data 
gid = www-data
socket = /tmp/sample_app.sock
chmod-socket = 664
vacuum = true

die-on-term = true

============================

nginx.conf:

============================

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

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/*;
}


#mail {
#   # See sample authentication script at:
#   # http://wiki.nginx.org/ImapAuthenticateWithApachePhpScript
# 
#   # auth_http localhost/auth.php;
#   # pop3_capabilities "TOP" "USER";
#   # imap_capabilities "IMAP4rev1" "UIDPLUS";
# 
#   server {
#       listen     localhost:110;
#       protocol   pop3;
#       proxy      on;
#   }
# 
#   server {
#       listen     localhost:143;
#       protocol   imap;
#       proxy      on;
#   }
#}

============================

sample_app_proxy:

============================

server {
 listen 80;
 server_name localhost;

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

============================

Answer 1

When used with Flask, Nginx is acting as a proxy server, which means there's no need to restart it when you want to reload your Flask app. It's the uWSGI that you need to take care of, since uWSGI is sitting in the middle between Flask app and Nginx and is responsible for forwarding all requests towards your app, and, well, running it.

Solution 1

One of the common approaches is to add following into uwsgi_conf.ini :

py-autoreload = 1

This will tell uWSGI that it needs to monitor file timestamps every second and reload the app once triggered.

Solution 2

Send graceful reload command to uWSGI Master FIFO :

Add following to your uwsgi_conf.ini :

master-fifo = /var/run/flask_uwsgi_fifo

And then reload uWSGI once you're done with your Flask source file changes:

$ echo r > /var/run/flask_uwsgi_fifo

Solution 3

Similar to solution 2 , but via touch-reload .

Add following to your uwsgi_conf.ini :

touch-reload = /var/run/flask_touch

And then reload your app via:

$ touch /var/run/flask_touch

Solution 4

Send SIGHUP to uWSGI pid file.

Add following to your uwsgi_conf.ini :

safe-pidfile = /tmp/flask.pid

And then reload your app via:

$ kill -HUP `cat /tmp/flask.pid`

or

$ uwsgi --reload /tmp/flask.pid

Answer 2

uwsgi is the part that hosts your application and so it is the part that needs to be restarted if the application changes.

For auto-reload, you could try this answer: https://stackoverflow.com/a/41529718/187292