Changes between Initial Version and Version 1 of TracModPython


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Sep 2, 2019, 11:30:15 AM (2 years ago)
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trac
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  • TracModPython

    v1 v1  
     1[[TracGuideToc]]
     2
     3= Trac and mod_python
     4
     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.
     7
     8[[PageOutline(2-3,Overview,inline)]]
     9
     10== Simple configuration: single project #Simpleconfiguration
     11
     12If you just installed mod_python, you may have to add a line to load the module in the Apache configuration:
     13{{{#!apache
     14LoadModule python_module modules/mod_python.so
     15}}}
     16
     17'''Note''': The exact path to the module depends on how the HTTPD installation is laid out.
     18
     19On Debian using apt-get:
     20{{{#!sh
     21apt-get install libapache2-mod-python libapache2-mod-python-doc
     22}}}
     23
     24Still on Debian, after you have installed mod_python, you must enable the modules in apache2, equivalent to the above Load Module directive:
     25{{{#!sh
     26a2enmod python
     27}}}
     28
     29On Fedora use, using yum:
     30{{{#!sh
     31yum install mod_python
     32}}}
     33
     34You 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+.
     35{{{#!apache
     36<Location /mpinfo>
     37  SetHandler mod_python
     38  PythonInterpreter main_interpreter
     39  PythonHandler mod_python.testhandler
     40  # For Apache 2.2
     41  <IfModule !mod_authz_core.c>
     42    Order allow,deny
     43    Allow from all
     44  </IfModule>
     45  # For Apache 2.4
     46  <IfModule mod_authz_core.c>
     47    Require all granted
     48  </IfModule>
     49</Location>
     50}}}
     51
     52A simple setup of Trac on mod_python looks like this:
     53{{{#!apache
     54<Location /projects/myproject>
     55  SetHandler mod_python
     56  PythonInterpreter main_interpreter
     57  PythonHandler trac.web.modpython_frontend
     58  PythonOption TracEnv /var/trac/myproject
     59  PythonOption TracUriRoot /projects/myproject
     60  # For Apache 2.2
     61  <IfModule !mod_authz_core.c>
     62    Order allow,deny
     63    Allow from all
     64  </IfModule>
     65  # For Apache 2.4
     66  <IfModule mod_authz_core.c>
     67    Require all granted
     68  </IfModule>
     69</Location>
     70}}}
     71
     72The 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.
     73
     74The options available are:
     75{{{#!apache
     76# For a single project
     77PythonOption TracEnv /var/trac/myproject
     78
     79# For multiple projects
     80PythonOption TracEnvParentDir /var/trac/myprojects
     81
     82# For the index of multiple projects
     83PythonOption TracEnvIndexTemplate /srv/www/htdocs/trac/project_list_template.html
     84
     85# A space delimitted list, with a "," between key and value pairs.
     86PythonOption TracTemplateVars key1,val1 key2,val2
     87
     88# Useful to get the date in the wanted order
     89PythonOption TracLocale en_GB.UTF8
     90
     91# See description above       
     92PythonOption TracUriRoot /projects/myproject
     93}}}
     94
     95=== Python Egg Cache
     96
     97Compressed 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:
     98{{{#!apache
     99PythonOption PYTHON_EGG_CACHE /var/trac/myprojects/egg-cache
     100}}}
     101
     102Or you can uncompress the Genshi egg to resolve problems extracting from it.
     103
     104=== Configuring Authentication
     105
     106See corresponding section in the [wiki:TracModWSGI#ConfiguringAuthentication] page.
     107
     108== Advanced Configuration
     109
     110=== Setting the Python Egg Cache
     111
     112If 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.
     113
     114{{{#!apache
     115<Location /projects/myproject>
     116  ...
     117  PythonOption PYTHON_EGG_CACHE /tmp
     118  ...
     119</Location>
     120}}}
     121
     122=== Setting the !PythonPath
     123
     124If 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:
     125{{{#!apache
     126<Location /projects/myproject>
     127  ...
     128  PythonPath "sys.path + ['/path/to/trac']"
     129  ...
     130</Location>
     131}}}
     132
     133Be careful about using the !PythonPath directive, and ''not'' `SetEnv PYTHONPATH`, as the latter won't work.
     134
     135=== Setting up multiple projects
     136
     137The Trac mod_python handler supports a configuration option similar to Subversion's `SvnParentPath`, called `TracEnvParentDir`:
     138{{{#!apache
     139<Location /projects>
     140  SetHandler mod_python
     141  PythonInterpreter main_interpreter
     142  PythonHandler trac.web.modpython_frontend
     143  PythonOption TracEnvParentDir /var/trac
     144  PythonOption TracUriRoot /projects
     145</Location>
     146}}}
     147
     148When 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.
     149
     150Directories residing in `TracEnvParentDir` that are not environment directories will display an error message on the [TracInterfaceCustomization#ProjectList project index page]. The directories can be excluded by listing them in a `.tracignore` file residing in `TracEnvParentDir`. Unix [https://docs.python.org/2/library/fnmatch.html shell-style wildcard patterns] can be used in the newline separated list of directories.
     151
     152If you don't want to have the subdirectory listing as your projects home page you can use a
     153{{{#!apache
     154<LocationMatch "/.+/">
     155}}}
     156
     157This 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.
     158
     159You can also use the same authentication realm for all of the projects using a `<LocationMatch>` directive:
     160{{{#!apache
     161<LocationMatch "/projects/[^/]+/login">
     162  AuthType Basic
     163  AuthName "Trac"
     164  AuthUserFile /var/trac/.htpasswd
     165  Require valid-user
     166</LocationMatch>
     167}}}
     168
     169=== Virtual Host Configuration
     170
     171Below is the sample configuration required to set up your Trac as a virtual server, ie when you access it at the URLs like
     172`http://trac.mycompany.com`:
     173
     174{{{#!apache
     175<VirtualHost *>
     176    DocumentRoot /var/www/myproject
     177    ServerName trac.mycompany.com
     178    <Location />
     179        SetHandler mod_python
     180        PythonInterpreter main_interpreter
     181        PythonHandler trac.web.modpython_frontend
     182        PythonOption TracEnv /var/trac/myproject
     183        PythonOption TracUriRoot /
     184    </Location>
     185    <Location /login>
     186        AuthType Basic
     187        AuthName "MyCompany Trac Server"
     188        AuthUserFile /var/trac/myproject/.htpasswd
     189        Require valid-user
     190    </Location>
     191</VirtualHost>
     192}}}
     193
     194This does not seem to work in all cases. What you can do if it does not:
     195 * Try using `<LocationMatch>` instead of `<Location>`.
     196 * `<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.
     197 * Depending on apache's `NameVirtualHost` configuration, you may need to use `<VirtualHost *:80>` instead of `<VirtualHost *>`.
     198
     199For a virtual host that supports multiple projects replace `TracEnv /var/trac/myproject` with `TracEnvParentDir /var/trac`.
     200
     201'''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".
     202
     203== Troubleshooting
     204
     205If you get server error pages, you can either check the Apache error log, or enable the `PythonDebug` option:
     206{{{#!apache
     207<Location /projects/myproject>
     208  ...
     209  PythonDebug on
     210</Location>
     211}}}
     212
     213For multiple projects, try restarting the server as well.
     214
     215=== Login Not Working
     216
     217If you've used `<Location />` directive, it will override any other directives, as well as `<Location /login>`.
     218The workaround is to use negation expression as follows (for multi project setups):
     219{{{#!apache
     220#this one for other pages
     221<Location ~ "/*(?!login)">
     222   SetHandler mod_python
     223   PythonHandler trac.web.modpython_frontend
     224   PythonOption TracEnvParentDir /projects
     225   PythonOption TracUriRoot /
     226</Location>
     227
     228#this one for login page
     229<Location ~ "/[^/]+/login">
     230   SetHandler mod_python
     231   PythonHandler trac.web.modpython_frontend
     232   PythonOption TracEnvParentDir /projects
     233   PythonOption TracUriRoot /
     234
     235   #remove these if you don't want to force SSL
     236   RewriteEngine On
     237   RewriteCond %{HTTPS} off
     238   RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
     239
     240   AuthType Basic
     241   AuthName "Trac"
     242   AuthUserFile /projects/.htpasswd
     243   Require valid-user
     244</Location>
     245}}}
     246
     247=== Expat-related segmentation faults === #expat
     248
     249This problem will most certainly hit you on Unix when using Python 2.4.
     250In 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.
     251As 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.
     252
     253=== Form submission problems
     254
     255If 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.
     256
     257=== Problem with virtual host configuration
     258
     259If 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.
     260
     261Using <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.
     262
     263=== Problem with zipped egg
     264
     265It'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:
     266
     267{{{#!sh
     268easy_install --always-unzip Trac-0.12b1.zip
     269}}}
     270
     271=== Using .htaccess
     272
     273Although 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.
     274
     275It 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.
     276
     277This also works out-of-box, with following trivial config:
     278{{{#!apache
     279SetHandler mod_python
     280PythonInterpreter main_interpreter
     281PythonHandler trac.web.modpython_frontend
     282PythonOption TracEnv /system/path/to/this/directory
     283PythonOption TracUriRoot /path/on/apache
     284
     285AuthType Basic
     286AuthName "ProjectName"
     287AuthUserFile /path/to/.htpasswd
     288Require valid-user
     289}}}
     290
     291The `TracUriRoot` is obviously the path you need to enter to the browser to get to Trac, eg `domain.tld/projects/trac`.
     292
     293=== Additional .htaccess help
     294
     295If 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:
     296
     297{{{#!apache
     298<IfModule mod_rewrite.c>
     299  RewriteEngine Off
     300</IfModule>
     301}}}
     302
     303=== Platform specific issues
     304==== Win32 Issues
     305
     306If 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.
     307
     308==== OS X issues
     309
     310When 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.
     311
     312==== SELinux issues
     313
     314If Trac reports something like: `Cannot get shared lock on db.lock`, then the security context on the repository may need to be set:
     315
     316{{{#!sh
     317chcon -R -h -t httpd_sys_content_t PATH_TO_REPOSITORY
     318}}}
     319
     320See also [http://subversion.apache.org/faq.html#reposperms How do I set repository permissions correctly?]
     321
     322==== FreeBSD issues
     323
     324The 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:
     325 * pysqlite requires threaded support in Python
     326 * mod_python requires a threadless install.
     327
     328Apache2 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.
     329The best option [http://modpython.org/pipermail/mod_python/2006-September/021983.html seems to be] adding to /usr/local/apache2/bin/ennvars the line:
     330
     331{{{#!sh
     332export LD_PRELOAD=/usr/lib/libc_r.so
     333}}}
     334
     335==== Fedora 7 Issues
     336
     337Make sure you install the 'python-sqlite2' package as it seems to be required for TracModPython, but not for tracd.
     338
     339=== Subversion issues
     340
     341If 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.
     342
     343If 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`).
     344
     345You 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:
     346{{{#!apache
     347PythonInterpreter main_interpreter
     348}}}
     349
     350This 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.
     351
     352=== Page layout issues
     353
     354If 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:
     355{{{#!apache
     356Alias /myproject/css "/usr/share/trac/htdocs/css"
     357<Location /myproject/css>
     358    SetHandler None
     359</Location>
     360}}}
     361
     362'''Note''': For the above configuration to have any effect it must be put after the configuration of your project root location, ie {{{<Location /myproject />}}}.
     363
     364=== HTTPS issues
     365
     366If 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:
     367{{{#!apache
     368<VirtualHost *>
     369    DocumentRoot /var/www/myproject
     370    ServerName trac.mycompany.com
     371    SetEnv HTTPS 1
     372    ....
     373</VirtualHost>
     374}}}
     375
     376=== Segmentation fault with php5-mhash or other php5 modules
     377
     378You 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].
     379
     380Some 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].
     381
     382----
     383See also: TracGuide, TracInstall, [wiki:TracModWSGI ModWSGI], [wiki:TracFastCgi FastCGI], [trac:TracNginxRecipe]