Changes between Initial Version and Version 1 of TracPlugins


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Timestamp:
Feb 16, 2019, 10:35:19 PM (3 years ago)
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trac
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  • TracPlugins

    v1 v1  
     1[[PageOutline(2-5,Contents,pullout)]]
     2
     3= Trac plugins
     4
     5Trac is extensible with [trac:PluginList plugins]. Plugin functionality is based on the [trac:TracDev/ComponentArchitecture component architecture], with special cases described in the [trac:TracDev/PluginDevelopment plugin development] page.
     6
     7== Plugin discovery
     8
     9From the user's point of view, a plugin is either a standalone .py file or a package (egg or wheel). Trac looks for plugins in Python's `site-packages` directory, the [TracIni#GlobalConfiguration global shared] `plugins` directory and the [TracEnvironment project environment] `plugins` directory. Components defined in globally-installed plugins must be explicitly enabled in the [[TracIni#components-section| [components] ]] section of the `trac.ini` file. Components defined in the `plugins` directory of the project environment are enabled, unless explicitly disabled in the `[components]` section of the `trac.ini` file.
     10
     11== Installing a Trac plugin
     12
     13The instructions below are applicable to a plugin packaged as an egg. Plugins implemented as a single `py` file should be downloaded and copied to the [TracEnvironment project environment] `plugins` directory or the [TracIni#GlobalConfiguration global shared] plugins directory.
     14
     15=== For a single project
     16
     17If you have downloaded a source distribution of a plugin, and want to build the `.egg` file:
     18
     19 * Unpack the source. It should provide `setup.py`.
     20 * Run:
     21 {{{#!sh
     22$ python setup.py bdist_egg
     23}}}
     24
     25You should now have an *.egg file. Examine the output of running Python to find where this was created.
     26
     27Once you have the plugin archive, copy it into the `plugins` directory of the [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 [TracStandalone "tracd" standalone server], restart tracd, ie kill the process and run again.
     28
     29To uninstall a plugin installed this way, remove the egg from the `plugins` directory and restart the web server.
     30
     31'''Note''': the Python version that the egg is built with ''must'' match the Python version with which Trac is run. For example, if you are running Trac under Python 2.6, but have upgraded your standalone Python to 2.7, the eggs won't be recognized.
     32
     33'''Note''': 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.
     34
     35=== For all projects
     36
     37==== With an .egg file
     38
     39Some plugins, such as [https://trac-hacks.org/wiki/TagsPlugin TracTags], are downloadable as an `.egg` file that can be installed with `easy_install` or `pip`:
     40{{{#!sh
     41$ easy_install TracTags
     42}}}
     43{{{#!sh
     44$ pip install TracTags
     45}}}
     46
     47If `easy_install` is not on your system, see the [trac:setuptools#Installsetuptools Trac setuptools documentation].
     48
     49`pip` is included in Python 2.7.9. 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 the [https://pip.pypa.io/en/latest/installing.html#install-pip get_pip.py].
     50
     51If Trac reports permission errors after installing a zipped egg, and you would rather not bother providing an 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`:
     52{{{#!sh
     53$ easy_install --always-unzip TracTags
     54}}}
     55You should end up with a directory having the same name as the zipped egg, complete with `.egg` extension, and containing its uncompressed contents.
     56
     57Trac also searches for plugins installed in the shared plugins directory, see TracIni#GlobalConfiguration. This is a convenient way to share the installation of plugins across several, but not all, environments.
     58
     59==== From source
     60
     61`easy_install` and `pip` make installing from source a snap. Just give it the URL to either a repository or a tarball/zip of the source:
     62{{{#!sh
     63$ easy_install https://trac-hacks.org/svn/tagsplugin/trunk
     64}}}
     65{{{#!sh
     66$ pip install svn+https://trac-hacks.org/svn/tagsplugin/trunk
     67}}}
     68When installing from a repository using `pip`, be sure to use the repository type in the protocol. For example, `svn+https` for Subversion and `git+https` for Git.
     69
     70==== Enabling the plugin
     71
     72Unlike plugins installed per environment, you'll have to explicitly enable globally installed plugins via [TracIni trac.ini]. This also applies to plugins installed in the shared plugins directory, ie the path specified in the [TracIni#inherit-plugins_dir-option "[inherit] plugins_dir"] configuration option.
     73
     74This is done in the [TracIni#components-section "[components]"] section of the configuration file `trac.ini`. For example:
     75{{{#!ini
     76[components]
     77tractags.* = enabled
     78}}}
     79
     80The 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`.
     81
     82After installing the plugin, you must restart your web server.
     83
     84==== Upgrading the environment
     85
     86Some plugins may 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:
     87
     88{{{#!sh
     89$ trac-admin /path/to/env upgrade
     90}}}
     91
     92A 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`.
     93
     94==== Redeploying static resources
     95
     96If you [TracInstall#MappingStaticResources mapped static resources] so they are served by the web server, and the plugin contains static resources (CSS, !JavaScript and image files), the resources will need to be deployed to the location on the filesystem that is served by the web server.
     97
     98Execute the `deploy` command, as was done during install and [TracUpgrade#a5.Refreshstaticresources upgrade]:
     99
     100{{{#!sh
     101$ trac-admin /path/to/env deploy /deploy/path
     102}}}
     103
     104After executing the command, you must restart your web server.
     105
     106{{{#!div style="border: 1pt dotted; margin: 1em"
     107**Note:** Some web browsers (IE, Opera) cache CSS and Javascript files, so you should instruct your users to manually erase the contents of their browser's cache. A forced refreshed (SHIFT + <F5>) should be enough.
     108{{{#!comment
     109Remove above note once #9936 is fixed.
     110}}}
     111}}}
     112
     113==== Upgrading a Plugin
     114
     115Normally, upgrading a plugin is simply a matter of repeating the install process. You may want to [#Uninstalling uninstall] old versions of the plugin.
     116
     117The `pip install` command has an `--upgrade (-U)` switch that will uninstall the old version and install the new version. The command can have some unintended side-effects though, because it will also upgrade the plugin dependencies. For example, if `Trac` is listed as a dependency of the plugin in `setup.py`, the latest version of Trac will be downloaded and installed. This may not be what you want if you are running an older version of Trac because not all your plugins are compatible with the latest version of Trac, or you simply haven't done the appropriate planning for upgrading Trac. Uninstalling and then installing the plugin can be a safer option:
     118{{{#!sh
     119$ pip uninstall <pluginname>
     120$ pip install <pluginname>
     121}}}
     122
     123Alternatively you can use a [https://pip.pypa.io/en/stable/user_guide/#requirements-files requirements file] and pin the versions of the packages that you don't want to implicitly upgrade.
     124
     125==== Uninstalling
     126
     127`pip` makes it easy to uninstall a plugin:
     128{{{#!sh
     129$ pip uninstall <pluginname>
     130}}}
     131
     132The `pip uninstall` command can be used even if the plugin was installed using `easy_install` or `python setup.py install`.
     133
     134Neither `easy_install` nor `python setup.py` have an uninstall feature. However, it is usually trivial to remove a globally installed egg and reference:
     135
     136 1. Do `easy_install -m <plugin name>` to remove references from `$PYTHONLIB/site-packages/easy-install.pth` when the plugin is installed by setuptools.
     137 1. Delete executables from `/usr/bin`, `/usr/local/bin`, or `C:\\Python*\Scripts`. To find what executables are involved, refer to the `[console-script]` section of `setup.py`.
     138 1. Delete the .egg file or folder from where it's installed, usually inside `$PYTHONLIB/site-packages/`.
     139 1. Restart the web server.
     140
     141If you are uncertain about the location of the egg file, you can try to locate it by replacing `myplugin` with whatever namespace the plugin uses (as used when enabling the plugin):
     142{{{#!pycon
     143>>> import myplugin
     144>>> print myplugin.__file__
     145/opt/local/python24/lib/site-packages/myplugin-0.4.2-py2.4.egg/myplugin/__init__.pyc
     146}}}
     147
     148== Setting up the plugin cache
     149
     150Some plugins will need to be extracted by the Python egg's runtime. See [wiki:TracInstall#egg-cache] for information on setting up the egg cache.
     151
     152== Web-based plugin administration
     153
     154The !WebAdmin interface offers limited support for plugin configuration to users with `TRAC_ADMIN` permission:
     155
     156* enabling and disabling installed plugins
     157* installing plugins by uploading them as eggs
     158
     159If you wish to disable the second function for security reasons, add the following to your `trac.ini` file:
     160{{{#!ini
     161[components]
     162trac.admin.web_ui.PluginAdminPanel = disabled
     163}}}
     164This disables the whole panel, so the first function will no longer be available either.
     165
     166== Writing Trac Plugins
     167
     168You can write your own Trac plugin using the following resources:
     169* [trac:TracDev Developer documentation]
     170* [https://trac-hacks.org Examples on trac-hacks.org]
     171* [trac:browser:branches/1.2-stable/sample-plugins sample-plugins]
     172
     173== Troubleshooting
     174
     175=== Is setuptools properly installed?
     176
     177Try this from the command line:
     178{{{#!sh
     179$ python -c "import pkg_resources"
     180}}}
     181
     182If you get '''no output''', setuptools '''is''' installed. Otherwise, you'll need to install it before plugins will work in Trac.
     183
     184=== Did you get the correct version of the Python egg?
     185
     186Python 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).
     187
     188Also, 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.
     189
     190=== Is the plugin enabled?
     191
     192If you install a plugin globally, ie ''not'' inside the `plugins` directory of the Trac project environment, you must explicitly enable it in [TracIni trac.ini]. Make sure that:
     193
     194 * you actually added the necessary line(s) to the `[components]` section.
     195 * the package/module names are correct and do not contain typos.
     196 * the value is "enabled", not "enable" or "Enable".
     197 * the section name is "components", not "component".
     198
     199=== Check the permissions on the .egg file
     200
     201Trac must be able to read the .egg file.
     202
     203=== Check the log files
     204
     205Enable [TracLogging logging] and set the log level to `DEBUG`, then watch the log file for messages about loading plugins.
     206
     207=== Verify you have the proper permissions
     208
     209Some plugins require you have special permissions in order to use them. !WebAdmin, for example, requires the user to have `TRAC_ADMIN` permissions for it to show up on the navigation bar.
     210
     211=== Is the wrong version of the plugin loading?
     212
     213If you put your plugins inside 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:
     214
     215 * Only one version of the plugin can be loaded for each running Trac server, ie 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.
     216 * 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.
     217 * 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 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.
     218 * Having more than one version listed inside Python site-packages is fine, ie installed with `setup.py install`, 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.
     219
     220=== If all of the above failed
     221
     222Okay, 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] or [trac:MailingList] and ask away!
     223
     224----
     225See also TracGuide, [trac:PluginList plugin list], [trac:TracDev/ComponentArchitecture component architecture].