- Plugin discovery
- Installing a Trac plugin
- Web-based plugin administration
- Setting up the plugin cache
- Writing Trac Plugins
Trac is extensible with plugins. Plugin functionality is based on the component architecture, described in the plugin development page.
From the user's point of view, a plugin is either a single .py file or a package (.egg or .whl). Trac looks for plugins in Python's
site-packages directory, the global shared
plugins directory and the project environment
plugins directory. Plugins installed to the project environment
plugins directory are enabled, unless explicitly disabled in the
[components] section of the
trac.ini file. Plugins installed elsewhere must be explicitly enabled in the [components] section of the
Installing a Trac plugin
The instructions below are applicable to a plugins installed as packages. Plugins implemented as a single
py file should be downloaded and copied to the project environment
plugins directory or the global shared plugins directory.
For a single project
Packages built for a single project must use the egg
format, as the wheel format (described below) is not
supported by the setuptools loading mechanism. Build the
egg file from the plugin source:
- Checkout or download and unpack the source.
- Change to the directory containing
The egg file will be created in the
$ python setup.py bdist_egg
- Copy the egg file to the
pluginsdirectory of the project environment.
Make sure the web server has sufficient permissions to read the plugin egg and restart the web server. If you are running as a "tracd" standalone server, restart tracd (i.e. kill the process and run again).
Trac also searches for plugins installed in the global shared plugins directory. This is a convenient way to share the installation of plugins across several, but not all, environments.
Note: The minor version number of the Python used to build the egg must match the minor version number of the Python running Trac. For example, if you are running Trac with Python 2.6, but build the egg with Python 2.7, the egg won't be recognized.
Note: In a multi-project setup, a pool of Python interpreters will be dynamically allocated to projects based on need. 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 projects. In other words, you cannot use different versions of a plugin in different projects of a multi-project setup. Install plugins for all projects (see below) and enable them as needed for each project.
Remove the egg from the
plugins directory and restart the web server.
For all projects
The modern Python package manager,
pip, is included in Python 2.7.9 and later. In earlier versions of Python it can be installed through the package manager of your OS (e.g.
apt-get install python-pip) or using get_pip.py.
pip, the plugin will be installed
in the wheel format, which is the modern standard for Python and a
replacement for the egg format.
Some plugins, such as [th:TagsPlugin TracTags], can be installed directly from PyPI using
$ pip install TracTags
The version can be specified, which can be useful if you don't want to install the latest:
$ pip install TracTags==0.10
You can install directly from a source repository:
$ pip install svn+https://trac-hacks.org/svn/tagsplugin/trunk
svn+ prefix with
git+ if installing
from a Git repository.
Or from the path or URL of a tar.gz or zip archive:
$ pip install https://trac-hacks.org/browser/tagsplugin/trunk?format=zip
Or checkout the source and provide
pip a path to the source directory:
$ svn co https://trac-hacks.org/svn/tagsplugin/trunk tractags $ pip install tractags
Enabling the plugin
Unlike plugins installed per environment, you have to explicitly enable globally installed plugins. This also applies to plugins installed in the shared plugins directory.
This is done in the
[components] section of the configuration file
trac.ini. For example:
[components] tractags.* = enabled
The name of the option is the plugin package name. This should be specified in the documentation of the plugin, but can also be discovered by looking at the source: it is usually the top-level directory name containing a file named
Plugins can also be enabled from the administration page.
After installing the plugin, you must restart your web server.
Upgrading the environment
Some plugins require an environment upgrade. This will typically be necessary for plugins that implement
IEnvironmentSetupParticipant. Common reasons for requiring an environment upgrade are to add tables to the database or add configuration parameters to trac.ini. A notification will be displayed when accessing Trac for the first time after installing a plugin and restarting the web server. To upgrade the environment, run the command:
$ trac-admin /path/to/env upgrade
A database backup will be made before upgrading the environment, unless the
--no-backup option is specified. For more information, refer to the documentation output by
trac-admin /path/to/env help upgrade.
Redeploying static resources
deploy command, as is done during install and upgrade:
$ trac-admin /path/to/env deploy /deploy/path
After executing the command, you must restart your web server.
Get a list of installed plugins:
$ pip list Package Version ---------- ------- Jinja2 2.10.1 MarkupSafe 1.1.1 pip 19.2.2 setuptools 41.2.0 Trac 1.4 TracTags 0.10 wheel 0.33.6
Uninstall a plugin by specifying the package name:
$ pip uninstall TracTags
Web-based plugin administration
The admin page offers limited support for plugin configuration to users with
- en/dis-abling installed plugins
- installing plugins by uploading them as eggs
If you wish to disable the second function for security reasons, add the following to your
[components] trac.admin.web_ui.PluginAdminPanel = disabled
This disables the whole panel, so the first function will no longer be available.
Setting up the plugin cache
Some plugins installed as eggs will need to be extracted by the Python egg's runtime (
pkg_resources), so that their contents are actual files on the file system. The directory to which they are extracted defaults to
.python-eggs in 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 PYTHON_EGG_CACHE /path/to/dir
This works whether you're using the CGI or the mod_python front-end. Put this directive next to where you set the path to the Trac environment, i.e. in the same
For example for CGI:
<Location /trac> SetEnv TRAC_ENV /path/to/projenv SetEnv PYTHON_EGG_CACHE /path/to/dir </Location>
Or for mod_python:
<Location /trac> SetHandler mod_python ... SetEnv PYTHON_EGG_CACHE /path/to/dir </Location>
Note: SetEnv requires the
mod_env module, which needs to be activated for Apache. In this case the SetEnv directive can also be used in the
mod_python Location block.
For FastCGI, you'll need to
-initial-env option, or whatever is provided by your web server for setting environment variables.
Note: if you already use -initial-env to set the project directory for either a single project or parent, you will need to add an additional -initial-env directive to the FastCgiConfig directive:
FastCgiConfig -initial-env TRAC_ENV=/var/lib/trac -initial-env PYTHON_EGG_CACHE=/var/lib/trac/plugin-cache
About hook scripts
If you have Subversion hook scripts that invoke Trac, such as the post-commit hook script provided in the
/contrib directory, make sure you define the
PYTHON_EGG_CACHE environment variable within these scripts.
Writing Trac Plugins
You can write your own Trac plugin using the following resources:
Did you get the correct version of the Python egg?
Python eggs have the Python version encoded in their filename. For example,
MyPlugin-1.0-py2.5.egg is an egg for Python 2.5, and will not be loaded if you're running a different Python version (such as 2.4 or 2.6).
Also, verify that the egg file you downloaded is indeed a .zip archive. If you downloaded it from a Trac site, you may have downloaded the HTML preview page instead.
Is the plugin enabled?
If you install a plugin globally, i.e. not inside the
plugins directory of the Trac project environment, you must explicitly enable it in trac.ini. Make sure that:
- you added the necessary line(s) to the
- the package/module names are correct and do not contain typos.
- the value is
- the section name is
Check the permissions
Trac must be able to read the .py file or package (.egg or .whl).
Check the log files
Verify you have the proper permissions
Some plugins require you have special permissions. TracTags, for example, requires
TAGS_VIEW permissions for the Tags navigation item to be added.
Is the wrong version of the plugin loading?
If you put your plugins in one of the
plugins directories, and certainly if you have more than one project, you need to make sure that the correct version of the plugin is loading. Here are some basic rules:
- Only one version of the plugin can be loaded for each running Trac server, i.e. each Python process. The Python namespaces and module list will be shared, and it cannot handle duplicates. Whether a plugin is
disabledmakes no difference.
- A globally installed plugin will override any version in the global or project plugins directories. A plugin from the global plugins directory will be discovered before any project plugins directory.
- If your Trac server hosts more than one project (as with
TRAC_ENV_PARENT_DIRsetups), having two versions of a plugin in two different projects will give unpredicatable results. Only one of them will load, and the one loaded will be shared by both projects. Trac will load the first plugin found, usually from the project that receives the first request.
- Having more than one version listed inside Python site-packages is fine, because setuptools will make sure you get the version installed most recently. However, don't store more than one version inside a global or project plugins directory: neither the version number nor the installed date will matter at all. There is no way to determine which one will be located first when Trac searches the directory for plugins.
If all of the above failed