Changes between Initial Version and Version 1 of TracPlugins


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Timestamp:
Feb 7, 2016, 1:07:44 AM (22 months ago)
Author:
trac
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  • TracPlugins

    v1 v1  
     1= Trac plugins =
     2[[TracGuideToc]]
     3
     4From version 0.9 onwards, Trac is extensible with [trac:PluginList plugins]. Plugin functionality is based on the [trac:TracDev/ComponentArchitecture component architecture], with peculiarities described in the [TracDev/PluginDevelopment plugin development] page.
     5
     6== Plugin discovery ==
     7
     8From the user's point of view, a plugin is either a standalone .py file or an .egg package. Trac looks for plugins in the global shared plugins directory (see [TracIni#GlobalConfiguration Global Configuration]) and in the `plugins` directory of the local TracEnvironment. Components defined in globally-installed plugins should be explicitly enabled in the [[TracIni#components-section| [components] ]] section of the trac.ini file.
     9
     10== Requirements for Trac eggs ==
     11
     12To use egg-based plugins in Trac, you need to have [http://peak.telecommunity.com/DevCenter/setuptools setuptools] (version 0.6) installed.
     13
     14To install `setuptools`, download the bootstrap module [http://peak.telecommunity.com/dist/ez_setup.py ez_setup.py] and execute it as follows:
     15
     16{{{
     17$ python ez_setup.py
     18}}}
     19
     20If 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.
     21
     22Plugins can also consist of a single `.py` file dropped directly into either the project's or the shared `plugins` directory.
     23
     24== Installing a Trac plugin ==
     25
     26=== For a single project ===
     27
     28Plugins are typically packaged as [http://peak.telecommunity.com/DevCenter/PythonEggs Python eggs]. That means they are .zip archives with the file extension `.egg`.
     29
     30If you have downloaded a source distribution of a plugin, and want to build the `.egg` file:
     31
     32 * Unpack the source. It should provide `setup.py`.
     33 * Run:
     34
     35{{{
     36$ python setup.py bdist_egg
     37}}}
     38
     39You should have a *.egg file. Examine the output of running python to find where this was created.
     40
     41Once you have the plugin archive, 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. Then restart the web server. If you are running as a [wiki:TracStandalone "tracd" standalone server], restart tracd (kill and run again).
     42
     43To uninstall a plugin installed this way, remove the egg from the `plugins` directory and restart the web server.
     44
     45Note: the Python version that the egg is built with ''must'' match the Python version with which Trac is run. For example, if you're running Trac under Python 2.5, but have upgraded your standalone Python to 2.6, the eggs won't be recognized.
     46
     47Note also: in a multi-project setup, a pool of Python interpreter instances 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 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.
     48
     49=== For all projects ===
     50
     51==== With an .egg file ====
     52
     53Some plugins (such as [trac:SpamFilter SpamFilter]) are downloadable as an `.egg` file that can be installed with the `easy_install` program:
     54{{{
     55easy_install TracSpamFilter
     56}}}
     57
     58If `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:\Python24\Scripts`) to their `PATH` environment variable (see [http://peak.telecommunity.com/DevCenter/EasyInstall#windows-notes easy_install Windows notes] for more information).
     59
     60If 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`:
     61{{{
     62easy_install --always-unzip TracSpamFilter-0.4.1_r10106-py2.6.egg
     63}}}
     64You should end up with a directory having the same name as the zipped egg (complete with `.egg` extension) and containing its uncompressed contents.
     65
     66Trac also searches for plugins installed in the shared plugins directory ''(since 0.10)''; see TracIni#GlobalConfiguration. This is a convenient way to share the installation of plugins across several, but not all, environments.
     67
     68==== From source ====
     69
     70`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:
     71{{{
     72easy_install http://svn.edgewall.com/repos/trac/plugins/0.12/spam-filter-captcha
     73}}}
     74
     75==== Enabling the plugin ====
     76
     77Unlike plugins installed per-environment, you'll have to explicitly enable globally installed plugins via [wiki:TracIni trac.ini]. This also applies to plugins installed in the shared plugins directory, i.e. the path specified in the `[inherit] plugins_dir` configuration option.
     78
     79This is done in the `[components]` section of the configuration file. For example:
     80{{{
     81[components]
     82tracspamfilter.* = enabled
     83}}}
     84
     85The 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`).
     86
     87Note: After installing the plugin, you must restart your web server.
     88
     89==== Uninstalling ====
     90
     91`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:
     92
     93 1. Do `easy_install -m [plugin name]` to remove references from `$PYTHONLIB/site-packages/easy-install.pth` when the plugin installed by setuptools.
     94 1. Delete executables from `/usr/bin`, `/usr/local/bin`, or `C:\\Python*\Scripts`. To find what executables are involved, refer to the `[console-script]` section of `setup.py`.
     95 1. Delete the .egg file or folder from where it's installed (usually inside `$PYTHONLIB/site-packages/`).
     96 1. Restart the web server.
     97
     98If you are uncertain about the location of the egg, here's a small tip to help locate an egg (or any package). Just replace `myplugin` with whatever namespace the plugin uses (as used when enabling the plugin):
     99{{{
     100>>> import myplugin
     101>>> print myplugin.__file__
     102/opt/local/python24/lib/site-packages/myplugin-0.4.2-py2.4.egg/myplugin/__init__.pyc
     103}}}
     104
     105== Setting up the plugin cache ==
     106
     107Some 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 `.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.
     108
     109To do this from the Apache configuration, use the `SetEnv` directive:
     110{{{
     111SetEnv PYTHON_EGG_CACHE /path/to/dir
     112}}}
     113
     114This works whether you're 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 `<Location>` block.
     115
     116For example (for CGI):
     117{{{
     118 <Location /trac>
     119   SetEnv TRAC_ENV /path/to/projenv
     120   SetEnv PYTHON_EGG_CACHE /path/to/dir
     121 </Location>
     122}}}
     123
     124Or (for mod_python):
     125{{{
     126 <Location /trac>
     127   SetHandler mod_python
     128   ...
     129   SetEnv PYTHON_EGG_CACHE /path/to/dir
     130 </Location>
     131}}}
     132
     133 ''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.''
     134
     135For [wiki:TracFastCgi FastCGI], you'll need to `-initial-env` option, or whatever is provided by your web server for setting environment variables.
     136
     137 ''Note: that 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. I.e.
     138
     139{{{
     140FastCgiConfig -initial-env TRAC_ENV=/var/lib/trac -initial-env PYTHON_EGG_CACHE=/var/lib/trac/plugin-cache
     141}}}
     142
     143=== About hook scripts ===
     144
     145If you've set up some subversion hook scripts that call the Trac engine, 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 as well.
     146
     147== Troubleshooting ==
     148
     149=== Is setuptools properly installed? ===
     150
     151Try this from the command line:
     152{{{
     153$ python -c "import pkg_resources"
     154}}}
     155
     156If you get '''no output''', setuptools '''is''' installed. Otherwise, you'll need to install it before plugins will work in Trac.
     157
     158=== Did you get the correct version of the Python egg? ===
     159
     160Python 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).
     161
     162Also, verify that the egg file you downloaded is indeed a .zip archive. If you downloaded it from a Trac site, chances are you downloaded the HTML preview page instead.
     163
     164=== Is the plugin enabled? ===
     165
     166If you install a plugin globally (i.e., ''not'' inside the `plugins` directory of the Trac project environment), you must explicitly enable it in [TracIni trac.ini]. Make sure that:
     167
     168 * ...you actually added the necessary line(s) to the `[components]` section.
     169 * ...the package/module names are correct.
     170 * ...the value is "enabled", not "enable" or "Enable".
     171 * ...the section name is "components", not "component".
     172
     173=== Check the permissions on the .egg file ===
     174
     175Trac must be able to read the .egg file.
     176
     177=== Check the log files ===
     178
     179Enable [wiki:TracLogging logging] and set the log level to `DEBUG`, then watch the log file for messages about loading plugins.
     180
     181=== Verify you have proper permissions ===
     182
     183Some plugins require you have special permissions in order to use them. [trac:WebAdmin WebAdmin], for example, requires the user to have TRAC_ADMIN permissions for it to show up on the navigation bar.
     184
     185=== Is the wrong version of the plugin loading? ===
     186
     187If you put your plugins inside 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:
     188
     189 * 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 `enabled` or `disabled` makes no difference.
     190 * A globally-installed plugin (typically `setup.py install`) will override any version in the global or project plugins directories. A plugin from the global plugins directory will be located ''before'' any project plugins directory.
     191 * If your Trac server hosts more than one project (as with `TRAC_ENV_PARENT_DIR` setups), having two versions of a plugin in two different projects will give uncertain 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.
     192 * Having more than one version listed inside Python site-packages is fine (i.e., installed with `setup.py install`) -- 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 version number nor 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.
     193
     194=== If all of the above failed ===
     195
     196Okay, so the logs don't mention plugins, the egg is readable, the Python version is correct, ''and'' the egg has been installed globally (and is enabled in trac.ini)... and it ''still'' doesn't work or give any error messages or any other indication as to why. Hop on the [trac:IrcChannel IrcChannel] and ask away!
     197
     198== Web-based plugin administration ==
     199
     200The WebAdmin plugin (part of the core since 0.11) offers limited support for plugin configuration through the web to users with `TRAC_ADMIN` permission:
     201
     202* en/disabling installed plugins
     203* installing plugins by uploading them as eggs
     204
     205You probably want to disable the second function for security reasons: in `trac.ini`, in the `[components]` section, add the line
     206{{{
     207trac.admin.web_ui.PluginAdminPanel = disabled
     208}}}
     209This disables the whole panel, so the first function will no longer be available either.
     210
     211----
     212See also TracGuide, [trac:PluginList plugin list], [trac:TracDev/ComponentArchitecture component architecture].