Deploying Flask (WSGI) Applications

Supporting files: https://github.com/mattupstate/flask-nyc-deploying

Transcript

1. Deploying Flask (WSGI) Applications
2. Matt Wright @mattupstate Engineer @ChatID • Python, Ruby, CoffeeScript • Flask, Chef, AngularJS Open Source • Flask-Security • Flask-Social • Flask-Mail + a few others
3. WSGI (Web Server Gateway Interface)
4. PEP 333 http://legacy.python.org/dev/peps/pep-0333/
5. # ~/hello.py def application(environ, start_response): start_response('200 OK', [('Content-Type','text/html')]) return ["Hello World"]
6. # ~/app.py from flask import Flask app = Flask(__name__) @app.route('/') @app.route('/<path:path>') def catch_all(path=''): return 'Hello World'
7. Browser WSGI Gateway WSGI App 1 2 4 3 Request Flow
8. Browser WSGI Gateway WSGI App 1 1. Browser sends an HTTP request to the gateway server Request Flow
9. Browser WSGI Gateway WSGI App 2 2. Gateway server prepares and sends the request to the WSGI compatible application 1 Request Flow
10. Browser WSGI Gateway WSGI App 1 2 3 3. Application processes the request and returns a response Request Flow
11. Browser WSGI Gateway WSGI App 1 2 4 3 4. The gateway server returns the response to the browser Request Flow
12. Browser WSGI Gateway WSGI Middle- ware WSGI App Middleware
13. Browser WSGI Gateway WSGI Middle- ware WSGI App WSGI Middle- ware WSGI Middle- ware WSGI Middle- ware WSGI Middle- ware MOAR MIDDLEWARE!
14. Gateway Servers (sometimes called “containers”)
15. http://www.tornadoweb.org/ Tornado
16. 1. Written in Python! 2. Web application framework 3. Asynchronous networking library 4. WSGI support Tornado
17. # ~/tor.py from tornado.wsgi import WSGIContainer from tornado.httpserver import HTTPServer from tornado.ioloop import IOLoop from app import app http_server = HTTPServer(WSGIContainer(app)) http_server.listen(8000) IOLoop.instance().start()
18. matt @ pc in ~/ $ mkvirtualenv wsgi matt @ pc in ~/ workon:wsgi $ pip install flask tornado matt @ pc in ~/ workon:wsgi $ python tor.py
19. matt @ pc in ~/ $ curl localhost:8000 Hello World matt @ pc in ~/ workon:wsgi $ pip install tornado matt @ pc in ~/ workon:wsgi $ python tor.py
20. http://www.gevent.org/ gevent
21. 1. Written in Python! 2. Coroutine networking library 3. 3rd party module support gevent
22. # ~/ge.py from gevent.wsgi import WSGIServer from app import app server = WSGIServer(('', 8000), app) server.serve_forever()
23. matt @ pc in ~/ workon:wsgi $ pip install gevent matt @ pc in ~/ workon:wsgi $ python ge.py
24. matt @ pc in ~/ $ curl localhost:8000 Hello World matt @ pc in ~/ workon:wsgi $ pip install gevent matt @ pc in ~/ workon:wsgi $ python ge.py 127.0.0.1 - - [2014-06-24...
25. http://gunicorn.org/ Gunicorn
26. Gunicorn 1. Written in Python! 2. Easy configuration 3. Broadly compatible 4. Extensible 5. Fairly speedy
27. matt @ pc in ~/ workon:wsgi $ pip install gunicorn matt @ pc in ~/ workon:wsgi $ gunicorn app:app
28. matt @ pc in ~/ $ curl localhost:8000 Hello World matt @ pc in ~/ $ mkvirtualenv wsgi matt @ pc in ~/ workon:wsgi $ pip install gunicorn flask matt @ pc in ~/ workon:wsgi $ gunicorn app:app
29. https://uwsgi-docs.readthedocs.org/ uWSGI
30. uWSGI 1. Support for many platforms and languages 2. Multiple configuration formats 3. Flexible logging 4. Extensible 5. Speaks HTTP and uwsgi
31. matt @ pc in ~/ workon:wsgi $ pip install uwsgi matt @ pc in ~/ workon:wsgi $ uwsgi --http :8000 -w app:app ... spawned uWSGI worker 1 ...
32. matt @ pc in ~/ $ curl localhost:8000 Hello World matt @ pc in ~/ workon:wsgi $ pip install uwsgi matt @ pc in ~/ workon:wsgi $ uwsgi --http :8000 -w app:app ... spawned uWSGI worker 1 ... [pid: 42176|app: 0|req: ...
33. (how to start your app) Process Management
34. http://upstart.ubuntu.com/ upstart
35. # /etc/init/hello-world.conf description "Hello World app" start on runlevel [2345] stop on runlevel [06] chdir /srv/hello-world exec /usr/local/bin/uwsgi \ --die-on-term \ --http :8000 \ -w app:app
36. http://www.freedesktop.org/wiki/Software/systemd/ systemd
37. # /etc/systemd/system/hello-world.service [Unit] Description=Hello World app [Service] ExecStart=/usr/local/bin/uwsgi \ --die-on-term \ --http :8000 \ -w app:app [Install] WantedBy=multi-user.target
38. http://supervisord.org/ supervisord
39. # /etc/supervisor.d/hello-world.conf [program:hello-world] directory=/srv/hello-world command=/usr/local/bin/uwsgi \ --die-on-term \ --http :8000 \ -w app:app
40. (some things are better than others) Reverse Proxies
41. Why? • Static files • URL rewrites • Routing • Header mods • App aggregation • and many more! • Network security • Authentication • Load balancing • SSL termination • Compression • Caching
42. http://www.nginx.org/ Apache
43. # /etc/apache2/sites-enabled/hello-world.conf <VirtualHost *:80> ServerName hello-world.com ProxyPreserveHost On ProxyPass /static ! Alias /static "/srv/hello-world/static" ProxyPass / http://127.0.0.1:8000/ ProxyPassReverse / http://127.0.0.1:8000/ </VirtualHost>
44. http://www.nginx.org/ Nginx
45. # /etc/nginx/sites-enabled/hello-world.conf server { listen 80; server_name hello-world.com; location / { proxy_pass http://127.0.0.1:8000; } location ^~ /static/ { root /srv/hello-world/static; } }
46. (is hard) Concurrency
47. Concurrency Models callback/generator (auto) lightweight threads (auto) processor/thread (config) processor/thread (config) Tornado gevent Gunicorn uWSGI
48. Increasing Concurrency processes processes workers + processes workers + processes Tornado gevent Gunicorn uWSGI
49. Increasing Workers Gunicorn uWSGI --workers <integer> --workers <integer>
50. DISCLAIMER!
51. (when one server isn’t enough) Load Balancing
52. Machine Level App Server 192.168.1.101 App Server 192.168.1.102 App Server 192.168.1.102 Primary Load Balancer 192.168.1.100
53. # /etc/nginx/sites-enabled/load-balancer.conf upstream app_upstream { least_conn; server 192.168.1.101:8000 server 192.168.1.102:8000 server 192.168.1.103:8000 } server { listen 80; server_name hello-world.com; location / { proxy_pass http://app_upstream; } }
54. Machine + Process Level App Server 192.168.1.101 App Server 192.168.1.102 App Server 192.168.1.102 Primary Load Balancer 192.168.1.100 t 127.0.0.1:8001 127.0.0.1:8002 127.0.0.1:8000 127.0.0.1:8000 127.0.0.1:8001 127.0.0.1:8002 127.0.0.1:8000 127.0.0.1:8001 127.0.0.1:8002
55. # /etc/supervisor.d/hello-world.conf [program:hello-world] numprocs=3 process_name=hello-world%(process_num) directory=/srv/hello-world command=/usr/local/bin/uwsgi \ --die-on-term \ --http :80%(process_num)02d \ -w app:app
56. # /etc/nginx/sites-enabled/hello-world.conf upstream local_upstream { least_conn; server 127.0.0.1:8000 server 127.0.0.1:8001 server 127.0.0.1:8002 } server { listen 80; server_name hello-world.com; location / { proxy_pass http://local_upstream; } }
57. (I’ve failed at this a lot) Recommendations
58. 1. Use virtualenv and pip 2. Don’t use virtualenvwrapper 3. Use a `requirements.txt` file Python
59. 1. Provide default settings 2. Enable settings to be overridden a. Environment Variable(s) b. Default file locations 3. Raise an error at startup when required settings are missing 4. Generate a `SECRET_KEY` with `os. urandom(16)` Configuration
60. 1. Prefer the uwsgi protocol over HTTP 2. Prefer TCP sockets over Unix sockets 3. Lots of useful options a. virtualenv + pythonpath b. enable-threads + lazy-apps c. need-app d. stats Use uWSGI
61. 1. Pass custom headers 2. Lots of useful modules a. ngx_http_geoip_module b. ngx_http_gzip_module c. ngx_http_memcached_module d. ngx_http_status_module Use Nginx
62. (putting it all together) Automation
63. http://www.ansible.com/ Ansible
64. (because what could go wrong?) Demo
65. Thank You! mattupstate.com gittip.com/mattupstate github.com/mattupstate twitter.com/mattupstate