Changes between Initial Version and Version 1 of TracPlugins


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Timestamp:
01/30/12 14:43:47 (6 years ago)
Author:
trac
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  • TracPlugins

    v1 v1  
     1= Trac Plugins = 
     2[[TracGuideToc]] 
     3 
     4Trac is extensible with [trac:PluginList plugins] since version 0.9. The plugin functionality is based on the [trac:TracDev/ComponentArchitecture component architecture] with peculiarities described at [TracDev/PluginDevelopment plugin development] page. 
     5 
     6== Plugin discovery == 
     7 
     8From the user point of view a Plugin is either standalone .py file or an .egg package. Trac looks for Plugins in a global shared plugins directory (see [TracIni#GlobalConfiguration Global Configuration]) and in `plugins` directory of 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$ python ez_setup.py 
     17}}} 
     18 
     19If 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. 
     20 
     21Plugins can also consist of a single `.py` file dropped directly into the root of environment's or into shared `plugins` directory. 
     22 
     23== Installing a Trac Plugin == 
     24 
     25=== For a Single Project === 
     26 
     27Plugins are packaged as [http://peak.telecommunity.com/DevCenter/PythonEggs Python eggs]. That means they are ZIP archives with the file extension `.egg`.  
     28 
     29If you have downloaded a source distribution of a plugin, and want to build the `.egg` file, follow this instruction: 
     30 * Unpack the source. It should provide a setup.py.  
     31 * Run: 
     32{{{ 
     33$ python setup.py bdist_egg 
     34}}} 
     35 
     36Then you will have a *.egg file. Examine the output of running python to find where this was created. 
     37 
     38Once 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. Then, restart the web server (this requirement was not previously mentioned in this document, but in my tests it began working only after I did so). 
     39 
     40To uninstall a plugin installed this way, remove the egg from `plugins` directory and restart web server. 
     41 
     42Note that the Python version that the egg is built with must 
     43match the Python version with which Trac is run.  If for 
     44instance you are running Trac under Python 2.5, but have 
     45upgraded your standalone Python to 2.6, the eggs won't be 
     46recognized. 
     47 
     48Note 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. 
     49 
     50=== For All Projects === 
     51 
     52==== With an .egg file ==== 
     53 
     54Some plugins (such as [trac:SpamFilter SpamFilter]) are downloadable as a `.egg` file which can be installed with the `easy_install` program: 
     55{{{ 
     56easy_install TracSpamFilter 
     57}}} 
     58 
     59If `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). 
     60 
     61If 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`: 
     62{{{ 
     63easy_install --always-unzip TracSpamFilter-0.4.1_r10106-py2.6.egg 
     64}}} 
     65You should end up with a directory having the same name as the zipped egg (complete with `.egg` extension) and containing its uncompressed contents. 
     66 
     67Trac 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. 
     68 
     69==== From source ==== 
     70 
     71`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: 
     72{{{ 
     73easy_install http://svn.edgewall.com/repos/trac/plugins/0.12/spam-filter-captcha 
     74}}} 
     75 
     76==== Enabling the plugin ==== 
     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 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 need to 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 1. Do `easy_install -m [plugin name]` to remove references from `$PYTHONLIB/site-packages/easy-install.pth` when the plugin installed by setuptools. 
     93 1. Delete executables from `/usr/bin`, `/usr/local/bin` or `C:\\Python*\Scripts`. For search what executables are there, you may refer to `[console-script]` section of `setup.py`. 
     94 1. Delete the .egg file or folder from where it is installed, usually inside `$PYTHONLIB/site-packages/`. 
     95 1. Restart web server. 
     96 
     97If 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): 
     98{{{ 
     99>>> import myplugin 
     100>>> print myplugin.__file__ 
     101/opt/local/python24/lib/site-packages/myplugin-0.4.2-py2.4.egg/myplugin/__init__.pyc 
     102}}} 
     103 
     104== Setting up the Plugin Cache == 
     105 
     106Some 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. 
     107 
     108To do this from the Apache configuration, use the `SetEnv` directive as follows: 
     109{{{ 
     110SetEnv PYTHON_EGG_CACHE /path/to/dir 
     111}}} 
     112 
     113This 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 `<Location>` block. 
     114 
     115For example (for CGI): 
     116{{{ 
     117 <Location /trac> 
     118   SetEnv TRAC_ENV /path/to/projenv 
     119   SetEnv PYTHON_EGG_CACHE /path/to/dir 
     120 </Location> 
     121}}} 
     122 
     123or (for mod_python): 
     124{{{ 
     125 <Location /trac> 
     126   SetHandler mod_python 
     127   ... 
     128   SetEnv PYTHON_EGG_CACHE /path/to/dir 
     129 </Location> 
     130}}} 
     131 
     132 ''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.'' 
     133 
     134For [wiki:TracFastCgi FastCGI], you'll need to `-initial-env` option, or whatever is provided by your web server for setting environment variables.  
     135 
     136 ''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. 
     137 
     138{{{ 
     139FastCgiConfig -initial-env TRAC_ENV=/var/lib/trac -initial-env PYTHON_EGG_CACHE=/var/lib/trac/plugin-cache 
     140}}} 
     141 
     142=== About hook scripts === 
     143 
     144If you have 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. 
     145 
     146== Troubleshooting == 
     147 
     148=== Is setuptools properly installed? === 
     149 
     150Try this from the command line: 
     151{{{ 
     152$ python -c "import pkg_resources" 
     153}}} 
     154 
     155If you get '''no output''', setuptools '''is''' installed. Otherwise, you'll need to install it before plugins will work in Trac. 
     156 
     157=== Did you get the correct version of the Python egg? === 
     158 
     159Python 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). 
     160 
     161Also, 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. 
     162 
     163=== Is the plugin enabled? === 
     164 
     165 
     166If you install a plugin globally (i.e. ''not'' inside the `plugins` directory of the Trac project environment) you will have to explicitly enable it in [TracIni trac.ini]. Make sure that: 
     167 * you actually added the necessary line(s) to the `[components]` section 
     168 * the package/module names are correct 
     169 * the value is “enabled", not e.g. “enable” 
     170 
     171=== Check the permissions on the egg file === 
     172 
     173Trac must be able to read the file.  
     174 
     175=== Check the log files === 
     176 
     177Enable [wiki:TracLogging logging] and set the log level to `DEBUG`, then watch the log file for messages about loading plugins. 
     178 
     179=== Verify you have proper permissions === 
     180 
     181Some 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. 
     182 
     183=== Is the wrong version of the plugin loading? === 
     184 
     185If 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: 
     186 * 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. 
     187 * A globally installed plugin (typically `setup.py install`) will override any version in global or project plugins directories. A plugin from the global plugins directory will be located before any project plugins directory. 
     188 * If your Trac server hosts more than one project (as with `TRAC_ENV_PARENT_DIR` setups), then 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 found - basically from the project that receives the first request. 
     189 * Having more than one version listed inside Python site-packages is fine (ie. 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. 
     190 
     191=== If all of the above failed === 
     192 
     193OK, 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 the 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. 
     194 
     195---- 
     196See also TracGuide, [trac:PluginList plugin list], [trac:TracDev/ComponentArchitecture component architecture]