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docs: add installation overview section
author Mads Kiilerich <madski@unity3d.com>
date Tue, 07 Apr 2015 02:53:04 +0200
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children 22a3fa3c4254
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5080:790da8154ef8 5081:154becd92f40
1 .. _overview:
2
3 =====================
4 Installation Overview
5 =====================
6
7
8 Some overview and some details that can help understanding the options when
9 installing Kallithea.
10
11
12 Python Environment
13 ------------------
14
15 **Kallithea** is written entirely in Python_ and requires Python version
16 2.6 or higher. Python 3.x is currently not supported.
17
18 Given a Python installation, there are different ways of providing the
19 environment for running Python applications. Each of them pretty much
20 corresponds to a ``site-packages`` directory somewhere where packages can be
21 installed.
22
23 Kallithea itself can be run from source or be installed, but even when running
24 from source, there are some dependencies that must be installed in the Python
25 environment used for running Kallithea.
26
27 - Packages *could* be installed in Python's ``site-packages`` directory ... but
28 that would require running pip_ as root and it would be hard to uninstall or
29 upgrade and is probably not a good idea unless using a package manager.
30
31 - Packages could also be installed in ``~/.local`` ... but that is probably
32 only a good idea if using a dedicated user per application or instance.
33
34 - Finally, it can be installed in a virtualenv_. That is a very lightweight
35 "container" where each Kallithea instance can get its own dedicated and
36 self-contained virtual environment.
37
38 We recommend using virtualenv for installing Kallithea.
39
40
41 Installation Methods
42 --------------------
43
44 Kallithea must be installed on a server. Kallithea is installed in a Python
45 environment so it can use packages that are installed there and make itself
46 available for other packages.
47
48 Two different cases will pretty much cover the options for how it can be
49 installed.
50
51 - The Kallithea source repository can be cloned and used - it is kept stable and
52 can be used in production. The Kallithea maintainers use the development
53 branch in production. The advantage of installation from source and regularly
54 updating it is that you take advantage of the most recent improvements. Using
55 it directly from a DVCS also means that it is easy to track local customizations.
56
57 Running ``setup.py develop`` in the source will use pip to install the
58 necessary dependencies in the Python environment and create a
59 ``.../site-packages/Kallithea.egg-link`` file there that points at the Kallithea
60 source.
61
62 - Kallithea can also be installed from ready-made packages using a package manager.
63 The official released versions are available on PyPI_ and can be downloaded and
64 installed with all dependencies using ``pip install kallithea``.
65
66 With this method, Kallithea is installed in the Python environment as any
67 other package, usually as a ``.../site-packages/Kallithea-X-py2.7.egg/``
68 directory with Python files and everything else that is needed.
69
70 (``pip install kallithea`` from a source tree will do pretty much the same
71 but build the Kallithea package itself locally instead of downloading it.)
72
73
74 Web Server
75 ----------
76
77 Kallithea is (primarily) a WSGI_ application that must be run from a web
78 server that expose WSGI as HTTP.
79
80 - Kallithea uses the Paste_ tool for some admin tasks. Paste provides ``paste
81 serve`` as a convenient way to launch Python WSGI / web servers.
82 This method is perfect for development but *can* also be used for production.
83
84 ``paste`` is a command line tool. Using it in production requires some way to
85 wrap it as a managable service.
86
87 Paste come with its own web server but Kallithea defaults to use Waitress_.
88 Gunicorn_ is also an option. These web servers have different limited feature
89 sets.
90
91 It is also common/mandatory to put another web server or (reverse) proxy in
92 front of these Python web servers. Nginx_ is a common choice. This simple
93 setup will thus often end up being quite complex.
94
95 The configuration of which web server to use is in the ini file passed to
96 ``paste``. The entry point for the WSGI application is configured in
97 ``setup.py`` as ``kallithea.config.middleware:make_app``.
98
99 - `Apache httpd`_ can serve WSGI applications directly using mod_wsgi_ and a
100 simple Python file with the necessary configuration. This is a good option if
101 Apache is an option.
102
103 - IIS_ can also server WSGI applications directly using isapi-wsgi_.
104
105 - UWSGI_ is also an option.
106
107 The best option depends on what you are familiar with and the requirements for
108 performance and stability. Also, keep in mind that Kallithea mainly is serving
109 custom data generated from relatively slow Python process. Kallithea is also
110 often used inside organizations with a limited amount of users and thus no
111 continuous hammering from the internet.
112
113
114 .. _Python: http://www.python.org/
115 .. _Gunicorn: http://gunicorn.org/
116 .. _Waitress: http://waitress.readthedocs.org/en/latest/
117 .. _virtualenv: http://pypi.python.org/pypi/virtualenv
118 .. _Paste: http://pythonpaste.org/
119 .. _PyPI: https://pypi.python.org/pypi
120 .. _Apache httpd: http://httpd.apache.org/
121 .. _mod_wsgi: https://code.google.com/p/modwsgi/
122 .. _isapi-wsgi: https://github.com/hexdump42/isapi-wsgi
123 .. _UWSGI: https://uwsgi-docs.readthedocs.org/en/latest/
124 .. _nginx: http://nginx.org/en/
125 .. _iis: http://en.wikipedia.org/wiki/Internet_Information_Services
126 .. _pip: http://en.wikipedia.org/wiki/Pip_%28package_manager%29
127 .. _WSGI: http://en.wikipedia.org/wiki/Web_Server_Gateway_Interface
128 .. _pylons: http://www.pylonsproject.org/