mirror of https://github.com/mitsuhiko/flask.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
101 lines
4.5 KiB
101 lines
4.5 KiB
.. _becomingbig: |
|
|
|
Becoming Big |
|
============ |
|
|
|
Here are your options when growing your codebase or scaling your application. |
|
|
|
Read the Source. |
|
---------------- |
|
|
|
Flask started in part to demonstrate how to build your own framework on top of |
|
existing well-used tools Werkzeug (WSGI) and Jinja (templating), and as it |
|
developed, it became useful to a wide audience. As you grow your codebase, |
|
don't just use Flask -- understand it. Read the source. Flask's code is |
|
written to be read; it's documentation is published so you can use its internal |
|
APIs. Flask sticks to documented APIs in upstream libraries, and documents its |
|
internal utilities so that you can find the hook points needed for your |
|
project. |
|
|
|
Hook. Extend. |
|
------------- |
|
|
|
The :ref:`api` docs are full of available overrides, hook points, and |
|
:ref:`signals`. You can provide custom classes for things like the request and |
|
response objects. Dig deeper on the APIs you use, and look for the |
|
customizations which are available out of the box in a Flask release. Look for |
|
ways in which your project can be refactored into a collection of utilities and |
|
Flask extensions. Explore the many `extensions |
|
<http://flask.pocoo.org/extensions/>`_ in the community, and look for patterns to |
|
build your own extensions if you do not find the tools you need. |
|
|
|
Subclass. |
|
--------- |
|
|
|
The :class:`~flask.Flask` class has many methods designed for subclassing. You |
|
can quickly add or customize behavior by subclassing :class:`~flask.Flask` (see |
|
the linked method docs) and using that subclass wherever you instantiate an |
|
application class. This works well with :ref:`app-factories`. |
|
|
|
Wrap with middleware. |
|
--------------------- |
|
|
|
The :ref:`app-dispatch` chapter shows in detail how to apply middleware. You |
|
can introduce WSGI middleware to wrap your Flask instances and introduce fixes |
|
and changes at the layer between your Flask application and your HTTP |
|
server. Werkzeug includes several `middlewares |
|
<http://werkzeug.pocoo.org/docs/middlewares/>`_. |
|
|
|
Fork. |
|
----- |
|
|
|
If none of the above options work, fork Flask. The majority of code of Flask |
|
is within Werkzeug and Jinja2. These libraries do the majority of the work. |
|
Flask is just the paste that glues those together. For every project there is |
|
the point where the underlying framework gets in the way (due to assumptions |
|
the original developers had). This is natural because if this would not be the |
|
case, the framework would be a very complex system to begin with which causes a |
|
steep learning curve and a lot of user frustration. |
|
|
|
This is not unique to Flask. Many people use patched and modified |
|
versions of their framework to counter shortcomings. This idea is also |
|
reflected in the license of Flask. You don't have to contribute any |
|
changes back if you decide to modify the framework. |
|
|
|
The downside of forking is of course that Flask extensions will most |
|
likely break because the new framework has a different import name. |
|
Furthermore integrating upstream changes can be a complex process, |
|
depending on the number of changes. Because of that, forking should be |
|
the very last resort. |
|
|
|
Scale like a pro. |
|
----------------- |
|
|
|
For many web applications the complexity of the code is less an issue than |
|
the scaling for the number of users or data entries expected. Flask by |
|
itself is only limited in terms of scaling by your application code, the |
|
data store you want to use and the Python implementation and webserver you |
|
are running on. |
|
|
|
Scaling well means for example that if you double the amount of servers |
|
you get about twice the performance. Scaling bad means that if you add a |
|
new server the application won't perform any better or would not even |
|
support a second server. |
|
|
|
There is only one limiting factor regarding scaling in Flask which are |
|
the context local proxies. They depend on context which in Flask is |
|
defined as being either a thread, process or greenlet. If your server |
|
uses some kind of concurrency that is not based on threads or greenlets, |
|
Flask will no longer be able to support these global proxies. However the |
|
majority of servers are using either threads, greenlets or separate |
|
processes to achieve concurrency which are all methods well supported by |
|
the underlying Werkzeug library. |
|
|
|
Discuss with the community. |
|
--------------------------- |
|
|
|
The Flask developers keep the framework accessible to users with codebases big |
|
and small. If you find an obstacle in your way, caused by Flask, don't hesitate |
|
to contact the developers on the mailinglist or IRC channel. The best way for |
|
the Flask and Flask extension developers to improve the tools for larger |
|
applications is getting feedback from users.
|
|
|