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Changes between Initial Version and Version 1 of TracPlugins

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02/23/08 22:54:25 (10 years ago)
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  • TracPlugins

    v1 v1  
     1= Trac Plugins = 
     2[[TracGuideToc]] 
     3 
     4Since version 0.9, Trac supports plugins that extend the built-in functionality. The plugin functionality is based on the [http://trac.edgewall.org/wiki/TracDev/ComponentArchitecture component architecture]. 
     5 
     6== Requirements == 
     7 
     8To use egg based plugins in Trac, you need to have [http://peak.telecommunity.com/DevCenter/setuptools setuptools] (version 0.6) installed. 
     9 
     10To install `setuptools`, download the bootstrap module [http://peak.telecommunity.com/dist/ez_setup.py ez_setup.py] and execute it as follows: 
     11{{{ 
     12$ python ez_setup.py 
     13}}} 
     14 
     15If 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. 
     16 
     17Plugins can also consist of a single `.py` file dropped into either the environment or global `plugins` directory ''(since [milestone:0.10])''. 
     18 
     19== Installing a Trac Plugin == 
     20 
     21=== For a Single Project === 
     22 
     23Plugins are packaged as [http://peak.telecommunity.com/DevCenter/PythonEggs Python eggs]. That means they are ZIP archives with the file extension `.egg`.  
     24 
     25If you have downloaded a source distribution of a plugin, and want to build the `.egg` file, follow this instruction: 
     26 * Unpack the source. It should provide a setup.py.  
     27 * Run: 
     28{{{ 
     29$ python setup.py bdist_egg 
     30}}} 
     31 
     32Then you will have a *.egg file. Examine the output of running python to find where this was created. 
     33 
     34Once 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. 
     35 
     36Note that the Python version that the egg is built with must 
     37match the Python version with which Trac is run.  If for 
     38instance you are running Trac under Python 2.3, but have 
     39upgraded your standalone Python to 2.4, the eggs won't be 
     40recognized. 
     41 
     42=== For All Projects === 
     43 
     44==== With an .egg file ==== 
     45 
     46Some plugins (such as [http://trac.edgewall.org/wiki/SpamFilter SpamFilter]) are downloadable as a `.egg` file which can be installed with the `easy_install` program: 
     47{{{ 
     48easy_install TracSpamFilter 
     49}}} 
     50 
     51If `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:\Python23\Scripts`) to their `PATH` environment variable (see [http://peak.telecommunity.com/DevCenter/EasyInstall#windows-notes easy_install Windows notes] for more information). 
     52 
     53If 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`: 
     54{{{ 
     55easy_install --always-unzip TracSpamFilter-0.2.1dev_r5943-py2.4.egg 
     56}}} 
     57You should end up with a directory having the same name as the zipped egg (complete with `.egg` extension) and containing its uncompressed contents. 
     58 
     59Trac also searches for globally installed plugins under `$PREFIX/share/trac/plugins` ''(since 0.10)''. 
     60 
     61==== From source ==== 
     62 
     63`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: 
     64{{{ 
     65easy_install http://svn.edgewall.com/repos/trac/sandbox/spam-filter 
     66}}} 
     67 
     68==== Enabling the plugin ==== 
     69Unlike 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: 
     70{{{ 
     71[components] 
     72tracspamfilter.* = enabled 
     73}}} 
     74 
     75The 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`.) 
     76 
     77Note: After installing the plugin, you need to restart your web server. 
     78 
     79== Setting up the Plugin Cache == 
     80 
     81Some 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. 
     82 
     83To do this from the Apache configuration, use the `SetEnv` directive as follows: 
     84{{{ 
     85SetEnv PYTHON_EGG_CACHE /path/to/dir 
     86}}} 
     87 
     88This 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. 
     89 
     90For example (for CGI): 
     91{{{ 
     92 <Location /trac> 
     93   SetEnv TRAC_ENV /path/to/projenv 
     94   SetEnv PYTHON_EGG_CACHE /path/to/dir 
     95 </Location> 
     96}}} 
     97 
     98or (for mod_python): 
     99{{{ 
     100 <Location /trac> 
     101   SetHandler mod_python 
     102   ... 
     103   SetEnv PYTHON_EGG_CACHE /path/to/dir 
     104 </Location> 
     105}}} 
     106 
     107 ''Note: this requires the `mod_env` module'' 
     108 
     109For [wiki:TracFastCgi FastCGI], you'll need to `-initial-env` option, or whatever is provided by your web server for setting environment variables.  
     110 
     111 ''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 atleast one environment variable inside trac.fcgi as expressed in the example on [wiki:TracFastCgi TracFastCgi]. 
     112 
     113=== About hook scripts === 
     114 
     115If 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. 
     116 
     117== Troubleshooting == 
     118 
     119=== Is setuptools properly installed? === 
     120 
     121Try this from the command line: 
     122{{{ 
     123$ python -c "import pkg_resources" 
     124}}} 
     125 
     126If you get '''no output''', setuptools '''is''' installed. Otherwise, you'll need to install it before plugins will work in Trac. 
     127 
     128=== Did you get the correct version of the Python egg? === 
     129 
     130Python eggs have the Python version encoded in their filename. For example, `MyPlugin-1.0-py2.4.egg` is an egg for Python 2.4, and will '''not''' be loaded if you're running a different Python version (such as 2.3 or 2.5). 
     131 
     132Also, 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. 
     133 
     134=== Is the plugin enabled? === 
     135 
     136If 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: 
     137 * you actually added the necessary line(s) to the `[components]` section 
     138 * the package/module names are correct 
     139 * the value is “enabled", not e.g. “enable” 
     140 
     141=== Check the permissions on the egg file === 
     142 
     143Trac must be able to read the file.  
     144 
     145=== Check the log files === 
     146 
     147Enable [wiki:TracLogging logging] and set the log level to `DEBUG`, then watch the log file for messages about loading plugins. 
     148 
     149=== Verify you have proper permissions === 
     150 
     151Some 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. 
     152 
     153=== Is the wrong version of the plugin loading? === 
     154 
     155If 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 som basic rules: 
     156 * 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. 
     157 * 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. 
     158 * 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. 
     159 * 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. 
     160 
     161=== If all of the above failed === 
     162 
     163OK, 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 IrcChannel and ask away. 
     164 
     165---- 
     166See also TracGuide, [http://trac.edgewall.org/wiki/PluginList plugin list], [http://trac.edgewall.org/wiki/TracDev/ComponentArchitecture component architecture]