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  • wiki/pages/TracModPython

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     3= Trac and mod_python
     5Mod_python is an [https://httpd.apache.org/ Apache] module that embeds the Python interpreter within the server, so that web-based applications in Python will run many times faster than traditional CGI and will have the ability to retain database connections.
     6Trac supports [http://www.modpython.org/ mod_python], which speeds up Trac's response times considerably, especially compared to [TracCgi CGI], and permits use of many Apache features not possible with [wiki:TracStandalone tracd]/mod_proxy.
     8These instructions are for Apache 2. If you are using Apache 1.3, you may have some luck with [trac:wiki:TracModPython2.7 TracModPython2.7], but that is a deprecated setup.
     12== Simple configuration: single project == #Simpleconfiguration
     14If you just installed mod_python, you may have to add a line to load the module in the Apache configuration:
     16LoadModule python_module modules/mod_python.so
     19'''Note''': The exact path to the module depends on how the HTTPD installation is laid out.
     21On Debian using apt-get:
     23apt-get install libapache2-mod-python libapache2-mod-python-doc
     26Still on Debian, after you have installed mod_python, you must enable the modules in apache2, equivalent to the above Load Module directive:
     28a2enmod python
     31On Fedora use, using yum:
     33yum install mod_python
     36You can test your mod_python installation by adding the following to your httpd.conf. You should remove this when you are done testing for security reasons. Note: mod_python.testhandler is only available in mod_python 3.2+.
     38<Location /mpinfo>
     39   SetHandler mod_python
     40   PythonInterpreter main_interpreter
     41   PythonHandler mod_python.testhandler
     42   Order allow,deny
     43   Allow from all
     47A simple setup of Trac on mod_python looks like this:
     49<Location /projects/myproject>
     50   SetHandler mod_python
     51   PythonInterpreter main_interpreter
     52   PythonHandler trac.web.modpython_frontend
     53   PythonOption TracEnv /var/trac/myproject
     54   PythonOption TracUriRoot /projects/myproject
     55   Order allow,deny
     56   Allow from all
     60The option '''`TracUriRoot`''' may or may not be necessary in your setup. Try your configuration without it; if the URLs produced by Trac look wrong, if Trac does not seem to recognize URLs correctly, or you get an odd "No handler matched request to..." error, add the '''`TracUriRoot`''' option. You will notice that the `Location` and '''`TracUriRoot`''' have the same path.
     62The options available are:
     64# For a single project
     65PythonOption TracEnv /var/trac/myproject
     67# For multiple projects
     68PythonOption TracEnvParentDir /var/trac/myprojects
     70# For the index of multiple projects
     71PythonOption TracEnvIndexTemplate /srv/www/htdocs/trac/project_list_template.html
     73# A space delimitted list, with a "," between key and value pairs.
     74PythonOption TracTemplateVars key1,val1 key2,val2
     76# Useful to get the date in the wanted order
     77PythonOption TracLocale en_GB.UTF8
     79# See description above       
     80PythonOption TracUriRoot /projects/myproject
     83=== Python Egg Cache
     85Compressed Python eggs like Genshi are normally extracted into a directory named `.python-eggs` in the users home directory. Since Apache's home usually is not writeable, an alternate egg cache directory can be specified like this:
     87PythonOption PYTHON_EGG_CACHE /var/trac/myprojects/egg-cache
     90Or you can uncompress the Genshi egg to resolve problems extracting from it.
     92=== Configuring Authentication
     94See corresponding section in the [wiki:TracModWSGI#ConfiguringAuthentication] page.
     96== Advanced Configuration
     98=== Setting the Python Egg Cache
     100If the Egg Cache isn't writeable by your Web server, you'll either have to change the permissions, or point Python to a location where Apache can write. This can manifest itself as a `500 internal server error` and/or a complaint in the syslog.
     103<Location /projects/myproject>
     104  ...
     105  PythonOption PYTHON_EGG_CACHE /tmp
     106  ...
     110=== Setting the !PythonPath
     112If the Trac installation isn't installed in your Python path, you will have to tell Apache where to find the Trac mod_python handler  using the `PythonPath` directive:
     114<Location /projects/myproject>
     115  ...
     116  PythonPath "sys.path + ['/path/to/trac']"
     117  ...
     121Be careful about using the !PythonPath directive, and ''not'' `SetEnv PYTHONPATH`, as the latter won't work.
     123=== Setting up multiple projects
     125The Trac mod_python handler supports a configuration option similar to Subversion's `SvnParentPath`, called `TracEnvParentDir`:
     127<Location /projects>
     128  SetHandler mod_python
     129  PythonInterpreter main_interpreter
     130  PythonHandler trac.web.modpython_frontend
     131  PythonOption TracEnvParentDir /var/trac
     132  PythonOption TracUriRoot /projects
     136When you request the `/projects` URL, you will get a listing of all subdirectories of the directory you set as `TracEnvParentDir` that look like Trac environment directories. Selecting any project in the list will bring you to the corresponding Trac environment.
     138If you don't want to have the subdirectory listing as your projects home page you can use a
     140<LocationMatch "/.+/">
     143This will instruct Apache to use mod_python for all locations different from root while having the possibility of placing a custom home page for root in your !DocumentRoot folder.
     145You can also use the same authentication realm for all of the projects using a `<LocationMatch>` directive:
     147<LocationMatch "/projects/[^/]+/login">
     148  AuthType Basic
     149  AuthName "Trac"
     150  AuthUserFile /var/trac/.htpasswd
     151  Require valid-user
     155=== Virtual Host Configuration
     157Below is the sample configuration required to set up your Trac as a virtual server, ie when you access it at the URLs like
     161<VirtualHost *>
     162    DocumentRoot /var/www/myproject
     163    ServerName trac.mycompany.com
     164    <Location />
     165        SetHandler mod_python
     166        PythonInterpreter main_interpreter
     167        PythonHandler trac.web.modpython_frontend
     168        PythonOption TracEnv /var/trac/myproject
     169        PythonOption TracUriRoot /
     170    </Location>
     171    <Location /login>
     172        AuthType Basic
     173        AuthName "MyCompany Trac Server"
     174        AuthUserFile /var/trac/myproject/.htpasswd
     175        Require valid-user
     176    </Location>
     180This does not seem to work in all cases. What you can do if it does not:
     181 * Try using `<LocationMatch>` instead of `<Location>`.
     182 * `<Location />` may, in your server setup, refer to the complete host instead of simple the root of the server. This means that everything (including the login directory referenced below) will be sent to Python and authentication does not work, ie you get the infamous Authentication information missing error. If this is the case, try using a sub-directory for Trac instead of the root, ie /web/ and /web/login instead of / and /login.
     183 * Depending on apache's `NameVirtualHost` configuration, you may need to use `<VirtualHost *:80>` instead of `<VirtualHost *>`.
     185For a virtual host that supports multiple projects replace `TracEnv /var/trac/myproject` with `TracEnvParentDir /var/trac`.
     187'''Note''': !DocumentRoot should not point to your Trac project env. As Asmodai wrote on #trac: "suppose there's a webserver bug that allows disclosure of !DocumentRoot they could then leech the entire Trac environment".
     189== Troubleshooting
     191If you get server error pages, you can either check the Apache error log, or enable the `PythonDebug` option:
     193<Location /projects/myproject>
     194  ...
     195  PythonDebug on
     199For multiple projects, try restarting the server as well.
     201=== Login Not Working
     203If you've used `<Location />` directive, it will override any other directives, as well as `<Location /login>`.
     204The workaround is to use negation expression as follows (for multi project setups):
     206#this one for other pages
     207<Location ~ "/*(?!login)">
     208   SetHandler mod_python
     209   PythonHandler trac.web.modpython_frontend
     210   PythonOption TracEnvParentDir /projects
     211   PythonOption TracUriRoot /
     214#this one for login page
     215<Location ~ "/[^/]+/login">
     216   SetHandler mod_python
     217   PythonHandler trac.web.modpython_frontend
     218   PythonOption TracEnvParentDir /projects
     219   PythonOption TracUriRoot /
     221   #remove these if you don't want to force SSL
     222   RewriteEngine On
     223   RewriteCond %{HTTPS} off
     224   RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
     226   AuthType Basic
     227   AuthName "Trac"
     228   AuthUserFile /projects/.htpasswd
     229   Require valid-user
     233=== Expat-related segmentation faults === #expat
     235This problem will most certainly hit you on Unix when using Python 2.4.
     236In Python 2.4, some version of [http://expat.sourceforge.net/ Expat] (an XML parser library written in C) is used and if Apache is using another version, this results in segmentation faults.
     237As Trac 0.11 is using Genshi, which will indirectly use Expat, that problem can now hit you even if everything was working fine before with Trac 0.10. This problem has not been reported for Python 2.5+, so best to upgrade.
     239=== Form submission problems
     241If you're experiencing problems submitting some of the forms in Trac (a common problem is that you get redirected to the start page after submission), check whether your {{{DocumentRoot}}} contains a folder or file with the same path that you mapped the mod_python handler to. For some reason, mod_python gets confused when it is mapped to a location that also matches a static resource.
     243=== Problem with virtual host configuration
     245If the <Location /> directive is used, setting the `DocumentRoot` may result in a ''403 (Forbidden)'' error. Either remove the `DocumentRoot` directive, or make sure that accessing the directory it points is allowed, in a corresponding `<Directory>` block.
     247Using <Location /> together with `SetHandler` resulted in having everything handled by mod_python, which leads to not being able to download any CSS or images/icons. Use <Location /trac> `SetHandler None` </Location> to circumvent the problem, though this may not be the most elegant solution.
     249=== Problem with zipped egg
     251It's possible that your version of mod_python will not import modules from zipped eggs. If you encounter an `ImportError: No module named trac` in your Apache logs but you think everything is where it should be, this might be your problem. Look in your site-packages directory; if the Trac module appears as a ''file'' rather than a ''directory'', then this might be your problem. To rectify this, try installing Trac using the `--always-unzip` option:
     254easy_install --always-unzip Trac-0.12b1.zip
     257=== Using .htaccess
     259Although it may seem trivial to rewrite the above configuration as a directory in your document root with a `.htaccess` file, this does not work. Apache will append a "/" to any Trac URLs, which interferes with its correct operation.
     261It may be possible to work around this with mod_rewrite, but I failed to get this working. In all, it is more hassle than it is worth.
     263This also works out-of-box, with following trivial config:
     265SetHandler mod_python
     266PythonInterpreter main_interpreter
     267PythonHandler trac.web.modpython_frontend
     268PythonOption TracEnv /system/path/to/this/directory
     269PythonOption TracUriRoot /path/on/apache
     271AuthType Basic
     272AuthName "ProjectName"
     273AuthUserFile /path/to/.htpasswd
     274Require valid-user
     277The `TracUriRoot` is obviously the path you need to enter to the browser to get to Trac, eg `domain.tld/projects/trac`.
     279=== Additional .htaccess help
     281If you are using the .htaccess method you may have additional problems if your Trac directory is inheriting .htaccess directives from another. This may also help to add to your .htaccess file:
     284<IfModule mod_rewrite.c>
     285  RewriteEngine Off
     289=== Platform specific issues
     290==== Win32 Issues
     292If you run Trac with mod_python < 3.2 on Windows, uploading attachments will '''not''' work. This problem is resolved in mod_python 3.1.4 or later, so please upgrade mod_python to fix this.
     294==== OS X issues
     296When using mod_python on OS X you will not be able to restart Apache using `apachectl restart`. This is apparently fixed in mod_python 3.2, so please upgrade mod_python to fix this.
     298==== SELinux issues
     300If Trac reports something like: `Cannot get shared lock on db.lock`, then the security context on the repository may need to be set:
     303chcon -R -h -t httpd_sys_content_t PATH_TO_REPOSITORY
     306See also [http://subversion.apache.org/faq.html#reposperms How do I set repository permissions correctly?]
     308==== FreeBSD issues
     310The FreeBSD ports have both the new and old versions of mod_python and SQLite, but earlier versions of pysqlite and mod_python won't integrate:
     311 * pysqlite requires threaded support in Python
     312 * mod_python requires a threadless install.
     314Apache2 does not automatically support threads on FreeBSD. You could force thread support when running `./configure` for Apache, using `--enable-threads`, but this isn´t recommended.
     315The best option [http://modpython.org/pipermail/mod_python/2006-September/021983.html seems to be] adding to /usr/local/apache2/bin/ennvars the line:
     318export LD_PRELOAD=/usr/lib/libc_r.so
     321==== Fedora 7 Issues
     323Make sure you install the 'python-sqlite2' package as it seems to be required for TracModPython, but not for tracd.
     325=== Subversion issues
     327If you get the following Trac error `Unsupported version control system "svn"` only under mod_python, though it works well on the command-line and even with TracStandalone, chances are that you forgot to add the path to the Python bindings with the [TracModPython#ConfiguringPythonPath PythonPath] directive. A better way is to add a link to the bindings in the Python `site-packages` directory, or create a `.pth` file in that directory.
     329If this is not the case, it's possible that you are using Subversion libraries that are binary incompatible with the Apache ones and an incompatibility of the `apr` libraries is usually the cause. In that case, you also won't be able to use the svn modules for Apache (`mod_dav_svn`).
     331You also need a recent version of `mod_python` in order to avoid a runtime error ({{{argument number 2: a 'apr_pool_t *' is expected}}}) due to the default usage of multiple sub-interpreters. Version 3.2.8 ''should'' work, though it's probably better to use the workaround described in [trac:#3371 #3371], in order to force the use of the main interpreter:
     333PythonInterpreter main_interpreter
     336This is also the recommended workaround for other issues seen when using the Python bindings for Subversion within mod_python ([trac:#2611 #2611], [trac:#3455 #3455]). See in particular Graham Dumpleton's comment in [trac:comment:9:ticket:3455 #3455] explaining the issue.
     338=== Page layout issues
     340If the formatting of the Trac pages look weird, chances are that the style sheets governing the page layout are not handled properly by the web server. Try adding the following lines to your Apache configuration:
     342Alias /myproject/css "/usr/share/trac/htdocs/css"
     343<Location /myproject/css>
     344    SetHandler None
     348'''Note''': For the above configuration to have any effect it must be put after the configuration of your project root location, ie {{{<Location /myproject />}}}.
     350Also, setting `PythonOptimize On` seems to mess up the page headers and footers, in addition to hiding the documentation for macros and plugins (see #Trac8956). Considering how little effect the option has, leave it `Off`.
     352=== HTTPS issues
     354If you want to run Trac fully under https you might find that it tries to redirect to plain http. In this case just add the following line to your Apache configuration:
     356<VirtualHost *>
     357    DocumentRoot /var/www/myproject
     358    ServerName trac.mycompany.com
     359    SetEnv HTTPS 1
     360    ....
     364=== Segmentation fault with php5-mhash or other php5 modules
     366You may encounter segfaults (reported on Debian etch) if php5-mhash module is installed. Try to remove it to see if this solves the problem. See [http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=411487 Debian bug report].
     368Some people also have troubles when using PHP5 compiled with its own third party libraries instead of system libraries. Check [http://www.djangoproject.com/documentation/modpython/#if-you-get-a-segmentation-fault Django segmentation fault].
     371See also: TracGuide, TracInstall, [wiki:TracModWSGI ModWSGI], [wiki:TracFastCgi FastCGI], [trac:TracNginxRecipe]
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