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Touch up and integrate docs on deploying Flask.

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Ron DuPlain 14 years ago
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  1. 23
      docs/deploying/cgi.rst
  2. 96
      docs/deploying/fastcgi.rst
  3. 15
      docs/deploying/index.rst
  4. 69
      docs/deploying/mod_wsgi.rst
  5. 34
      docs/deploying/others.rst
  6. 31
      docs/deploying/uwsgi.rst

23
docs/deploying/cgi.rst
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@ -1,23 +1,20 @@
CGI
===
If all other deployment methods do not work, CGI will work for sure. CGI
is supported by all major servers but usually has a less-than-optimal
If all other deployment methods do not work, CGI will work for sure.
CGI is supported by all major servers but usually has a sub-optimal
performance.
This is also the way you can use a Flask application on Google's
`App Engine`_, there however the execution does happen in a CGI-like
environment. The application's performance is unaffected because of that.
This is also the way you can use a Flask application on Google's `App
Engine`_, where execution happens in a CGI-like environment.
.. admonition:: Watch Out
Please make sure in advance that your ``app.run()`` call you might
have in your application file, is inside an ``if __name__ ==
'__main__':`` or moved to a separate file. Just make sure it's not
called because this will always start a local WSGI server which we do
not want if we deploy that application to CGI / app engine.
.. _App Engine: http://code.google.com/appengine/
Please make sure in advance that any ``app.run()`` calls you might
have in your application file are inside an ``if __name__ ==
'__main__':`` block or moved to a separate file. Just make sure it's
not called because this will always start a local WSGI server which
we do not want if we deploy that application to CGI / app engine.
Creating a `.cgi` file
----------------------
@ -45,3 +42,5 @@ In Apache for example you can put a like like this into the config:
ScriptAlias /app /path/to/the/application.cgi
For more information consult the documentation of your webserver.
.. _App Engine: http://code.google.com/appengine/

96
docs/deploying/fastcgi.rst
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@ -1,20 +1,22 @@
.. _deploying-fastcgi:
FastCGI
=======
A very popular deployment setup on servers like `lighttpd`_ and `nginx`_
is FastCGI. To use your WSGI application with any of them you will need
a FastCGI server first.
The most popular one is `flup`_ which we will use for this guide. Make
sure to have it installed.
FastCGI is a deployment option on servers like `nginx`_, `lighttpd`_,
and `cherokee`_; see :ref:`deploying-uwsgi` and
:ref:`deploying-other-servers` for other options. To use your WSGI
application with any of them you will need a FastCGI server first. The
most popular one is `flup`_ which we will use for this guide. Make sure
to have it installed to follow along.
.. admonition:: Watch Out
Please make sure in advance that your ``app.run()`` call you might
have in your application file, is inside an ``if __name__ ==
'__main__':`` or moved to a separate file. Just make sure it's not
called because this will always start a local WSGI server which we do
not want if we deploy that application to FastCGI.
Please make sure in advance that any ``app.run()`` calls you might
have in your application file are inside an ``if __name__ ==
'__main__':`` block or moved to a separate file. Just make sure it's
not called because this will always start a local WSGI server which
we do not want if we deploy that application to FastCGI.
Creating a `.fcgi` file
-----------------------
@ -25,14 +27,14 @@ First you need to create the FastCGI server file. Let's call it
#!/usr/bin/python
from flup.server.fcgi import WSGIServer
from yourapplication import app
if __name__ == '__main__':
WSGIServer(app).run()
This is enough for Apache to work, however nginx and older versions of
lighttpd need a socket to be explicitly passed to communicate with the FastCGI
server. For that to work you need to pass the path to the socket to the
:class:`~flup.server.fcgi.WSGIServer`::
lighttpd need a socket to be explicitly passed to communicate with the
FastCGI server. For that to work you need to pass the path to the
socket to the :class:`~flup.server.fcgi.WSGIServer`::
WSGIServer(application, bindAddress='/path/to/fcgi.sock').run()
@ -72,22 +74,23 @@ A basic FastCGI configuration for lighttpd looks like that::
"^(/static.*)$" => "$1",
"^(/.*)$" => "/yourapplication.fcgi$1"
Remember to enable the FastCGI, alias and rewrite modules. This configuration
binds the application to `/yourapplication`. If you want the application to
work in the URL root you have to work around a lighttpd bug with the
Remember to enable the FastCGI, alias and rewrite modules. This
configuration binds the application to `/yourapplication`. If you want
the application to work in the URL root you have to work around a
lighttpd bug with the
:class:`~werkzeug.contrib.fixers.LighttpdCGIRootFix` middleware.
Make sure to apply it only if you are mounting the application the URL
root. Also, see the Lighty docs for more information on `FastCGI and Python
<http://redmine.lighttpd.net/wiki/lighttpd/Docs:ModFastCGI>`_ (note that
explicitly passing a socket to run() is no longer necessary).
root. Also, see the Lighty docs for more information on `FastCGI and
Python <http://redmine.lighttpd.net/wiki/lighttpd/Docs:ModFastCGI>`_
(note that explicitly passing a socket to run() is no longer necessary).
Configuring nginx
-----------------
Installing FastCGI applications on nginx is a bit different because by default
no FastCGI parameters are forwarded.
Installing FastCGI applications on nginx is a bit different because by
default no FastCGI parameters are forwarded.
A basic flask FastCGI configuration for nginx looks like this::
@ -101,9 +104,9 @@ A basic flask FastCGI configuration for nginx looks like this::
fastcgi_pass unix:/tmp/yourapplication-fcgi.sock;
}
This configuration binds the application to `/yourapplication`. If you want
to have it in the URL root it's a bit simpler because you don't have to figure
out how to calculate `PATH_INFO` and `SCRIPT_NAME`::
This configuration binds the application to `/yourapplication`. If you
want to have it in the URL root it's a bit simpler because you don't
have to figure out how to calculate `PATH_INFO` and `SCRIPT_NAME`::
location / { try_files $uri @yourapplication; }
location @yourapplication {
@ -113,9 +116,17 @@ out how to calculate `PATH_INFO` and `SCRIPT_NAME`::
fastcgi_pass unix:/tmp/yourapplication-fcgi.sock;
}
Since Nginx doesn't load FastCGI apps, you have to do it by yourself. You
can either write an `init.d` script for that or execute it inside a screen
session::
Running FastCGI Processes
-------------------------
Since Nginx and others do not load FastCGI apps, you have to do it by
yourself. `Supervisor can manage FastCGI processes.
<http://supervisord.org/configuration.html#fcgi-program-x-section-settings>`_
You can look around for other FastCGI process managers or write a script
to run your `.fcgi` file at boot, e.g. using a SysV ``init.d`` script.
For a temporary solution, you can always run the ``.fcgi`` script inside
GNU screen. See ``man screen`` for details, and note that this is a
manual solution which does not persist across system restart::
$ screen
$ /var/www/yourapplication/yourapplication.fcgi
@ -123,14 +134,14 @@ session::
Debugging
---------
FastCGI deployments tend to be hard to debug on most webservers. Very often the
only thing the server log tells you is something along the lines of "premature
end of headers". In order to debug the application the only thing that can
really give you ideas why it breaks is switching to the correct user and
executing the application by hand.
FastCGI deployments tend to be hard to debug on most webservers. Very
often the only thing the server log tells you is something along the
lines of "premature end of headers". In order to debug the application
the only thing that can really give you ideas why it breaks is switching
to the correct user and executing the application by hand.
This example assumes your application is called `application.fcgi` and that your
webserver user is `www-data`::
This example assumes your application is called `application.fcgi` and
that your webserver user is `www-data`::
$ su www-data
$ cd /var/www/yourapplication
@ -139,14 +150,15 @@ webserver user is `www-data`::
File "yourapplication.fcgi", line 4, in <module>
ImportError: No module named yourapplication
In this case the error seems to be "yourapplication" not being on the python
path. Common problems are:
In this case the error seems to be "yourapplication" not being on the
python path. Common problems are:
- relative paths being used. Don't rely on the current working directory
- the code depending on environment variables that are not set by the
- Relative paths being used. Don't rely on the current working directory
- The code depending on environment variables that are not set by the
web server.
- different python interpreters being used.
- Different python interpreters being used.
.. _lighttpd: http://www.lighttpd.net/
.. _nginx: http://nginx.org/
.. _lighttpd: http://www.lighttpd.net/
.. _cherokee: http://www.cherokee-project.com/
.. _flup: http://trac.saddi.com/flup

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docs/deploying/index.rst
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Deployment Options
==================
Depending on what you have available there are multiple ways to run Flask
applications. A very common method is to use the builtin server during
development and maybe behind a proxy for simple applications, but there
are more options available.
Depending on what you have available there are multiple ways to run
Flask applications. You can use the builtin server during development,
but you should use a full deployment option for production applications.
(Do not use the builtin development server in production.) Several
options are available and documented here.
If you have a different WSGI server look up the server documentation about
how to use a WSGI app with it. Just remember that your application object
is the actual WSGI application.
If you have a different WSGI server look up the server documentation
about how to use a WSGI app with it. Just remember that your
:class:`Flask` application object is the actual WSGI application.
.. toctree::
:maxdepth: 2

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docs/deploying/mod_wsgi.rst
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@ -3,35 +3,34 @@
mod_wsgi (Apache)
=================
If you are using the `Apache`_ webserver you should consider using `mod_wsgi`_.
If you are using the `Apache`_ webserver, consider using `mod_wsgi`_.
.. admonition:: Watch Out
Please make sure in advance that your ``app.run()`` call you might
have in your application file, is inside an ``if __name__ ==
'__main__':`` or moved to a separate file. Just make sure it's not
called because this will always start a local WSGI server which we do
not want if we deploy that application to mod_wsgi.
Please make sure in advance that any ``app.run()`` calls you might
have in your application file are inside an ``if __name__ ==
'__main__':`` block or moved to a separate file. Just make sure it's
not called because this will always start a local WSGI server which
we do not want if we deploy that application to mod_wsgi.
.. _Apache: http://httpd.apache.org/
Installing `mod_wsgi`
---------------------
If you don't have `mod_wsgi` installed yet you have to either install it using
a package manager or compile it yourself.
If you don't have `mod_wsgi` installed yet you have to either install it
using a package manager or compile it yourself. The mod_wsgi
`installation instructions`_ cover source installations on UNIX systems.
The mod_wsgi `installation instructions`_ cover source installations on UNIX
systems.
If you are using Ubuntu/Debian you can apt-get it and activate it as follows:
If you are using Ubuntu/Debian you can apt-get it and activate it as
follows:
.. sourcecode:: text
# apt-get install libapache2-mod-wsgi
On FreeBSD install `mod_wsgi` by compiling the `www/mod_wsgi` port or by using
pkg_add:
On FreeBSD install `mod_wsgi` by compiling the `www/mod_wsgi` port or by
using pkg_add:
.. sourcecode:: text
@ -40,8 +39,8 @@ pkg_add:
If you are using pkgsrc you can install `mod_wsgi` by compiling the
`www/ap2-wsgi` package.
If you encounter segfaulting child processes after the first apache reload you
can safely ignore them. Just restart the server.
If you encounter segfaulting child processes after the first apache
reload you can safely ignore them. Just restart the server.
Creating a `.wsgi` file
-----------------------
@ -61,14 +60,15 @@ instance you can directly import that one as `application`.
Store that file somewhere that you will find it again (e.g.:
`/var/www/yourapplication`) and make sure that `yourapplication` and all
the libraries that are in use are on the python load path. If you don't
want to install it system wide consider using a `virtual python`_ instance.
want to install it system wide consider using a `virtual python`_
instance.
Configuring Apache
------------------
The last thing you have to do is to create an Apache configuration file for
your application. In this example we are telling `mod_wsgi` to execute the
application under a different user for security reasons:
The last thing you have to do is to create an Apache configuration file
for your application. In this example we are telling `mod_wsgi` to
execute the application under a different user for security reasons:
.. sourcecode:: apache
@ -100,15 +100,16 @@ If your application does not run, follow this guide to troubleshoot:
**Problem:** application does not run, errorlog shows SystemExit ignored
You have a ``app.run()`` call in your application file that is not
guarded by an ``if __name__ == '__main__':`` condition. Either remove
that :meth:`~flask.Flask.run` call from the file and move it into a
separate `run.py` file or put it into such an if block.
guarded by an ``if __name__ == '__main__':`` condition. Either
remove that :meth:`~flask.Flask.run` call from the file and move it
into a separate `run.py` file or put it into such an if block.
**Problem:** application gives permission errors
Probably caused by your application running as the wrong user. Make
sure the folders the application needs access to have the proper
privileges set and the application runs as the correct user (``user``
and ``group`` parameter to the `WSGIDaemonProcess` directive)
privileges set and the application runs as the correct user
(``user`` and ``group`` parameter to the `WSGIDaemonProcess`
directive)
**Problem:** application dies with an error on print
Keep in mind that mod_wsgi disallows doing anything with
@ -127,10 +128,10 @@ If your application does not run, follow this guide to troubleshoot:
sys.stdout = sys.stderr
**Problem:** accessing resources gives IO errors
Your application probably is a single .py file you symlinked into the
site-packages folder. Please be aware that this does not work,
instead you either have to put the folder into the pythonpath the file
is stored in, or convert your application into a package.
Your application probably is a single .py file you symlinked into
the site-packages folder. Please be aware that this does not work,
instead you either have to put the folder into the pythonpath the
file is stored in, or convert your application into a package.
The reason for this is that for non-installed packages, the module
filename is used to locate the resources and for symlinks the wrong
@ -139,9 +140,9 @@ If your application does not run, follow this guide to troubleshoot:
Support for Automatic Reloading
-------------------------------
To help deployment tools you can activate support for automatic reloading.
Whenever something changes the `.wsgi` file, `mod_wsgi` will reload all
the daemon processes for us.
To help deployment tools you can activate support for automatic
reloading. Whenever something changes the `.wsgi` file, `mod_wsgi` will
reload all the daemon processes for us.
For that, just add the following directive to your `Directory` section:
@ -154,8 +155,8 @@ Working with Virtual Environments
Virtual environments have the advantage that they never install the
required dependencies system wide so you have a better control over what
is used where. If you want to use a virtual environment with mod_wsgi you
have to modify your `.wsgi` file slightly.
is used where. If you want to use a virtual environment with mod_wsgi
you have to modify your `.wsgi` file slightly.
Add the following lines to the top of your `.wsgi` file::

34
docs/deploying/others.rst
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@ -1,11 +1,11 @@
.. _deploying-other-servers:
Other Servers
=============
There are popular servers written in Python that allow the execution of
WSGI applications as well. Keep in mind though that some of these servers
were written for very specific applications and might not work as well for
standard WSGI application such as Flask powered ones.
There are popular servers written in Python that allow the execution of WSGI
applications as well. These servers stand alone when they run; you can proxy
to them from your web server.
Tornado
--------
@ -15,12 +15,12 @@ server and tools that power `FriendFeed`_. Because it is non-blocking and
uses epoll, it can handle thousands of simultaneous standing connections,
which means it is ideal for real-time web services. Integrating this
service with Flask is a trivial task::
from tornado.wsgi import WSGIContainer
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
from yourapplication import app
http_server = HTTPServer(WSGIContainer(app))
http_server.listen(5000)
IOLoop.instance().start()
@ -29,7 +29,6 @@ service with Flask is a trivial task::
.. _Tornado: http://www.tornadoweb.org/
.. _FriendFeed: http://friendfeed.com/
Gevent
-------
@ -47,7 +46,6 @@ event loop::
.. _greenlet: http://codespeak.net/py/0.9.2/greenlet.html
.. _libevent: http://monkey.org/~provos/libevent/
Gunicorn
--------
@ -57,19 +55,25 @@ and `greenlet`_. Running a Flask application on this server is quite simple::
gunicorn myproject:app
`Gunicorn`_ provides many command-line options -- see ``gunicorn -h``.
For example, to run a Flask application with 4 worker processes (``-w
4``) binding to localhost port 4000 (``-b 127.0.0.1:4000``)::
gunicorn -w 4 -b 127.0.0.1:4000 myproject:app
.. _Gunicorn: http://gunicorn.org/
.. _eventlet: http://eventlet.net/
.. _greenlet: http://codespeak.net/py/0.9.2/greenlet.html
Proxy Setups
------------
If you deploy your application behind an HTTP proxy you will need to
rewrite a few headers in order for the application to work. The two
problematic values in the WSGI environment usually are `REMOTE_ADDR` and
`HTTP_HOST`. Werkzeug ships a fixer that will solve some common setups,
but you might want to write your own WSGI middleware for specific setups.
If you deploy your application using one of these servers behind an HTTP
proxy you will need to rewrite a few headers in order for the
application to work. The two problematic values in the WSGI environment
usually are `REMOTE_ADDR` and `HTTP_HOST`. Werkzeug ships a fixer that
will solve some common setups, but you might want to write your own WSGI
middleware for specific setups.
The most common setup invokes the host being set from `X-Forwarded-Host`
and the remote address from `X-Forwarded-For`::

31
docs/deploying/uwsgi.rst
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@ -1,21 +1,25 @@
.. _deploying-uwsgi:
uWSGI
=====
A newly popular deployment method on servers like `cherokee`_ and `nginx`_
is uWSGI. To use your WSGI application with uWSGI protocol you will need
a uWSGI server first. uWSGI is both a protocol and an application server;
the application server can serve uWSGI, FastCGI, and HTTP protocols.
uWSGI is a deployment option on servers like `nginx`_, `lighttpd`_, and
`cherokee`_; see :ref:`deploying-fastcgi` and
:ref:`deploying-other-servers` for other options. To use your WSGI
application with uWSGI protocol you will need a uWSGI server
first. uWSGI is both a protocol and an application server; the
application server can serve uWSGI, FastCGI, and HTTP protocols.
The most popular server is `uwsgi`_, which we will use for this guide.
Make sure to have it installed.
The most popular uWSGI server is `uwsgi`_, which we will use for this
guide. Make sure to have it installed to follow along.
.. admonition:: Watch Out
Please make sure in advance that your ``app.run()`` call you might
have in your application file, is inside an ``if __name__ ==
'__main__':`` or moved to a separate file. Just make sure it's not
called because this will always start a local WSGI server which we do
not want if we deploy that application to uWSGI.
Please make sure in advance that any ``app.run()`` calls you might
have in your application file are inside an ``if __name__ ==
'__main__':`` block or moved to a separate file. Just make sure it's
not called because this will always start a local WSGI server which
we do not want if we deploy that application to uWSGI.
Starting your app with uwsgi
----------------------------
@ -50,7 +54,7 @@ A basic flask uWSGI configuration for nginx looks like this::
This configuration binds the application to `/yourapplication`. If you want
to have it in the URL root it's a bit simpler because you don't have to tell
it the WSGI `SCRIPT_NAME` or set the uwsgi modifer to make use of it::
it the WSGI `SCRIPT_NAME` or set the uwsgi modifier to make use of it::
location / { try_files $uri @yourapplication; }
location @yourapplication {
@ -58,6 +62,7 @@ it the WSGI `SCRIPT_NAME` or set the uwsgi modifer to make use of it::
uwsgi_pass unix:/tmp/uwsgi.sock;
}
.. _cherokee: http://www.cherokee-project.com/
.. _nginx: http://nginx.org/
.. _lighttpd: http://www.lighttpd.net/
.. _cherokee: http://www.cherokee-project.com/
.. _uwsgi: http://projects.unbit.it/uwsgi/

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