= Trac Plugins =
Since version 0.9, Trac supports [PluginList plugins] that extend the built-in functionality. The plugin functionality is based on the [trac:TracDev/ComponentArchitecture component architecture].
== Requirements ==
To use egg based plugins in Trac, you need to have [http://peak.telecommunity.com/DevCenter/setuptools setuptools] (version 0.6) installed.
To install `setuptools`, download the bootstrap module [http://peak.telecommunity.com/dist/ez_setup.py ez_setup.py] and execute it as follows:
$ python ez_setup.py
If the `ez_setup.py` script fails to install the setuptools release, you can download it from [http://www.python.org/pypi/setuptools PyPI] and install it manually.
Plugins can also consist of a single `.py` file dropped into either the environment or global `plugins` directory ”(since [milestone:0.10])”. See TracIni#GlobalConfiguration .
== Installing a Trac Plugin ==
=== For a Single Project ===
Plugins are packaged as [http://peak.telecommunity.com/DevCenter/PythonEggs Python eggs]. That means they are ZIP archives with the file extension `.egg`.
If you have downloaded a source distribution of a plugin, and want to build the `.egg` file, follow this instruction:
* Unpack the source. It should provide a setup.py.
$ python setup.py bdist_egg
Then you will have a *.egg file. Examine the output of running python to find where this was created.
Once you have the plugin archive, you need to copy it into the `plugins` directory of the [wiki:TracEnvironment project environment]. Also, make sure that the web server has sufficient permissions to read the plugin egg.
To uninstall a plugin installed this way, remove the egg from `plugins` directory and restart web server.
Note that the Python version that the egg is built with must
match the Python version with which Trac is run. If for
instance you are running Trac under Python 2.3, but have
upgraded your standalone Python to 2.4, the eggs won’t be
Note also that in a multi-project setup, a pool of Python interpreter instances will be dynamically allocated to projects based on need, and since plugins occupy a place in Python’s module system, the first version of any given plugin to be loaded will be used for all the projects. In other words, you cannot use different versions of a single plugin in two projects of a multi-project setup. It may be safer to install plugins for all projects (see below) and then enable them selectively on a project-by-project basis.
=== For All Projects ===
==== With an .egg file ====
Some plugins (such as [trac:SpamFilter SpamFilter]) are downloadable as a `.egg` file which can be installed with the `easy_install` program:
If `easy_install` is not on your system see the Requirements section above to install it. Windows users will need to add the `Scripts` directory of their Python installation (for example, `C:Python23Scripts`) to their `PATH` environment variable (see [http://peak.telecommunity.com/DevCenter/EasyInstall#windows-notes easy_install Windows notes] for more information).
If Trac reports permission errors after installing a zipped egg and you would rather not bother providing a egg cache directory writable by the web server, you can get around it by simply unzipping the egg. Just pass `–always-unzip` to `easy_install`:
easy_install –always-unzip TracSpamFilter-0.2.1dev_r5943-py2.4.egg
You should end up with a directory having the same name as the zipped egg (complete with `.egg` extension) and containing its uncompressed contents.
Trac also searches for globally installed plugins ”(since 0.10)”, see TracIni#GlobalConfiguration.
==== From source ====
`easy_install` makes installing from source a snap. Just give it the URL to either a Subversion repository or a tarball/zip of the source:
==== Enabling the plugin ====
Unlike plugins installed per-environment, you’ll have to explicitly enable globally installed plugins via [wiki:TracIni trac.ini]. This is done in the `[components]` section of the configuration file, for example:
tracspamfilter.* = enabled
The name of the option is the Python package of the plugin. This should be specified in the documentation of the plugin, but can also be easily discovered by looking at the source (look for a top-level directory that contains a file named `__init__.py`.)
Note: After installing the plugin, you need to restart your web server.
==== Uninstalling ====
`easy_install` or `python setup.py` does not have an uninstall feature. Hower, it is usually quite trivial to remove a globally installed egg and reference:
1. Do `easy_install -m [plugin name]` to remove references from `$PYTHONLIB/site-packages/easy-install.pth` when the plugin installed by setuptools.
1. Delete executables from `/usr/bin`, `/usr/local/bin` or `C:\Python*Scripts`. For search what executables are there, you may refer to `[console-script]` section of `setup.py`.
1. Delete the .egg file or folder from where it is installed, usually inside `$PYTHONLIB/site-packages/`.
1. Restart web server.
If you are uncertain about the location of the egg, here is a small tip to help locate an egg (or any package) – replace `myplugin` with whatever namespace the plugin uses (as used when enabling the plugin):
>>> import myplugin
>>> print myplugin.__file__
== Setting up the Plugin Cache ==
Some plugins will need to be extracted by the Python eggs runtime (`pkg_resources`), so that their contents are actual files on the file system. The directory in which they are extracted defaults to the home directory of the current user, which may or may not be a problem. You can however override the default location using the `PYTHON_EGG_CACHE` environment variable.
To do this from the Apache configuration, use the `SetEnv` directive as follows:
SetEnv PYTHON_EGG_CACHE /path/to/dir
This works whether you are using the [wiki:TracCgi CGI] or the [wiki:TracModPython mod_python] front-end. Put this directive next to where you set the path to the [wiki:TracEnvironment Trac environment], i.e. in the same `