Changes between Initial Version and Version 1 of TracModPython


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Timestamp:
Dec 23, 2012, 2:31:47 PM (5 years ago)
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trac
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  • TracModPython

    v1 v1  
     1= Trac and mod_python =
     2[[TracGuideToc]]
     3
     4Trac 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.
     5
     6{{{#!div class="important"
     7** A Word of Warning **
     8
     9As of 16^th^ June 2010, the mod_python project is officially dead.  If you are considering using mod_python for a new installation, '''please don't'''!  There are known issues which will not be fixed and there are now better alternatives.  Check out the main TracInstall pages for your target version for more information.
     10}}}
     11
     12
     13These instructions are for Apache 2; if you are still using Apache 1.3, you may have some luck with [trac:wiki:TracModPython2.7 TracModPython2.7], but you'll be totally on your own.
     14
     15[[PageOutline(2-3,Overview,inline)]]
     16
     17== Simple configuration: single project == #Simpleconfiguration
     18
     19If you just installed mod_python, you may have to add a line to load the module in the Apache configuration:
     20{{{
     21LoadModule python_module modules/mod_python.so
     22}}}
     23
     24''Note: The exact path to the module depends on how the HTTPD installation is laid out.''
     25
     26On Debian using apt-get
     27{{{
     28apt-get install libapache2-mod-python libapache2-mod-python-doc
     29}}}
     30(Still on Debian) after you have installed mod_python, you must enable the modules in apache2 (equivalent of the above Load Module directive):
     31{{{
     32a2enmod python
     33}}}
     34On Fedora use, using yum:
     35{{{
     36yum install mod_python
     37}}}
     38You 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+.
     39{{{
     40#!xml
     41<Location /mpinfo>
     42   SetHandler mod_python
     43   PythonInterpreter main_interpreter
     44   PythonHandler mod_python.testhandler
     45   Order allow,deny
     46   Allow from all
     47</Location>
     48}}}
     49
     50A simple setup of Trac on mod_python looks like this:
     51{{{
     52#!xml
     53<Location /projects/myproject>
     54   SetHandler mod_python
     55   PythonInterpreter main_interpreter
     56   PythonHandler trac.web.modpython_frontend
     57   PythonOption TracEnv /var/trac/myproject
     58   PythonOption TracUriRoot /projects/myproject
     59   Order allow,deny
     60   Allow from all
     61</Location>
     62}}}
     63
     64The 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.
     65
     66The options available are
     67{{{
     68    # For a single project
     69    PythonOption TracEnv /var/trac/myproject
     70
     71    # For multiple projects
     72    PythonOption TracEnvParentDir /var/trac/myprojects
     73
     74    # For the index of multiple projects
     75    PythonOption TracEnvIndexTemplate /srv/www/htdocs/trac/project_list_template.html
     76
     77    # A space delimitted list, with a "," between key and value pairs.
     78    PythonOption TracTemplateVars key1,val1 key2,val2
     79
     80    # Useful to get the date in the wanted order
     81    PythonOption TracLocale en_GB.UTF8
     82
     83    # See description above       
     84    PythonOption TracUriRoot /projects/myproject
     85}}}
     86
     87=== Python Egg Cache ===
     88
     89Compressed 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 writable an alternate egg cache directory can be specified like this:
     90{{{
     91PythonOption PYTHON_EGG_CACHE /var/trac/myprojects/egg-cache
     92}}}
     93
     94or you can uncompress the Genshi egg to resolve problems extracting from it.
     95
     96=== Configuring Authentication ===
     97
     98See corresponding section in the [wiki:TracModWSGI#ConfiguringAuthentication] page.
     99
     100
     101== Advanced Configuration
     102
     103=== Setting the Python Egg Cache ===
     104
     105If 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.
     106
     107{{{
     108#!xml
     109<Location /projects/myproject>
     110  ...
     111  PythonOption PYTHON_EGG_CACHE /tmp
     112  ...
     113</Location>
     114}}}
     115
     116
     117=== Setting the !PythonPath ===
     118
     119If the Trac installation isn't installed in your Python path, you'll have to tell Apache where to find the Trac mod_python handler  using the `PythonPath` directive:
     120{{{
     121#!xml
     122<Location /projects/myproject>
     123  ...
     124  PythonPath "sys.path + ['/path/to/trac']"
     125  ...
     126</Location>
     127}}}
     128
     129Be careful about using the !PythonPath directive, and ''not'' `SetEnv PYTHONPATH`, as the latter won't work.
     130
     131=== Setting up multiple projects ===
     132
     133The Trac mod_python handler supports a configuration option similar to Subversion's `SvnParentPath`, called `TracEnvParentDir`:
     134{{{
     135#!xml
     136<Location /projects>
     137  SetHandler mod_python
     138  PythonInterpreter main_interpreter
     139  PythonHandler trac.web.modpython_frontend
     140  PythonOption TracEnvParentDir /var/trac
     141  PythonOption TracUriRoot /projects
     142</Location>
     143}}}
     144
     145When 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.
     146
     147If you don't want to have the subdirectory listing as your projects home page you can use a
     148{{{
     149#!xml
     150<LocationMatch "/.+/">
     151}}}
     152
     153This 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.
     154
     155You can also use the same authentication realm for all of the projects using a `<LocationMatch>` directive:
     156{{{
     157#!xml
     158<LocationMatch "/projects/[^/]+/login">
     159  AuthType Basic
     160  AuthName "Trac"
     161  AuthUserFile /var/trac/.htpasswd
     162  Require valid-user
     163</LocationMatch>
     164}}}
     165
     166=== Virtual Host Configuration ===
     167
     168Below is the sample configuration required to set up your trac as a virtual server (i.e. when you access it at the URLs like
     169!http://trac.mycompany.com):
     170
     171{{{
     172#!xml
     173<VirtualHost * >
     174    DocumentRoot /var/www/myproject
     175    ServerName trac.mycompany.com
     176    <Location />
     177        SetHandler mod_python
     178        PythonInterpreter main_interpreter
     179        PythonHandler trac.web.modpython_frontend
     180        PythonOption TracEnv /var/trac/myproject
     181        PythonOption TracUriRoot /
     182    </Location>
     183    <Location /login>
     184        AuthType Basic
     185        AuthName "MyCompany Trac Server"
     186        AuthUserFile /var/trac/myproject/.htpasswd
     187        Require valid-user
     188    </Location>
     189</VirtualHost>
     190}}}
     191
     192This does not seem to work in all cases. What you can do if it does not:
     193 * Try using `<LocationMatch>` instead of `<Location>`
     194 * <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 (i.e. you get the infamous Authentication information missing error). If this applies to you, try using a sub-directory for trac instead of the root (i.e. /web/ and /web/login instead of / and /login).
     195 * Depending on apache's `NameVirtualHost` configuration, you may need to use `<VirtualHost *:80>` instead of `<VirtualHost *>`.
     196
     197For a virtual host that supports multiple projects replace "`TracEnv`" /var/trac/myproject with "`TracEnvParentDir`" /var/trac/
     198
     199Note: !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".
     200
     201== Troubleshooting ==
     202
     203In general, if you get server error pages, you can either check the Apache error log, or enable the `PythonDebug` option:
     204{{{
     205#!xml
     206<Location /projects/myproject>
     207  ...
     208  PythonDebug on
     209</Location>
     210}}}
     211
     212For multiple projects, try restarting the server as well.
     213
     214===Login Not Working===
     215If you've used <Location /> directive, it will override any other directives, as well as <Location /Login>.
     216The workaround is to use negation expression as follows (for multi project setups):
     217{{{
     218#!xml
     219#this one for other pages
     220<Location ~ "/*(?!login)">
     221   SetHandler mod_python
     222   PythonHandler trac.web.modpython_frontend
     223   PythonOption TracEnvParentDir /projects
     224   PythonOption TracUriRoot /
     225
     226</Location>
     227#this one for login page
     228<Location ~ "/[^/]+/login">
     229   SetHandler mod_python
     230   PythonHandler trac.web.modpython_frontend
     231   PythonOption TracEnvParentDir /projects
     232   PythonOption TracUriRoot /
     233
     234   #remove these if you don't want to force SSL
     235   RewriteEngine On
     236   RewriteCond %{HTTPS} off
     237   RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
     238
     239   AuthType Basic
     240   AuthName "Trac"
     241   AuthUserFile /projects/.htpasswd
     242   Require valid-user
     243</Location>
     244}}}
     245
     246=== Expat-related segmentation faults === #expat
     247
     248This problem will most certainly hit you on Unix when using Python 2.4.
     249In Python 2.4, some version of Expat (an XML parser library written in C) is used,
     250and 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
     252can now hit you even if everything was working fine before with Trac 0.10.
     253
     254See Graham Dumpleton's detailed [http://www.dscpl.com.au/wiki/ModPython/Articles/ExpatCausingApacheCrash explanation and workarounds] for the issue.
     255
     256=== Form submission problems ===
     257
     258If 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.
     259
     260=== Problem with virtual host configuration ===
     261
     262If 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).
     263
     264Using <Location /> together with `SetHandler` resulted in having everything handled by mod_python, which leads to not being able download any CSS or images/icons. I used <Location /trac> `SetHandler None` </Location> to circumvent the problem, though I do not know if this is the most elegant solution.
     265
     266=== Problem with zipped egg ===
     267
     268It'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, try installing Trac using the `--always-unzip` option, like this:
     269
     270{{{
     271easy_install --always-unzip Trac-0.12b1.zip
     272}}}
     273
     274=== Using .htaccess ===
     275
     276Although 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.
     277
     278It 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. Stick to the provided instructions. :)
     279
     280A success story: For me it worked out-of-box, with following trivial config:
     281{{{#!xml
     282SetHandler mod_python
     283PythonInterpreter main_interpreter
     284PythonHandler trac.web.modpython_frontend
     285PythonOption TracEnv /system/path/to/this/directory
     286PythonOption TracUriRoot /path/on/apache
     287
     288AuthType Basic
     289AuthName "ProjectName"
     290AuthUserFile /path/to/.htpasswd
     291Require valid-user
     292}}}
     293
     294The `TracUriRoot` is obviously the path you need to enter to the browser to get to the trac (e.g. domain.tld/projects/trac)
     295
     296=== Additional .htaccess help ===
     297
     298If 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:
     299
     300{{{
     301<IfModule mod_rewrite.c>
     302  RewriteEngine Off
     303</IfModule>
     304}}}
     305
     306=== Platform specific issues
     307==== Win32 Issues ====
     308If 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.
     309
     310
     311==== OS X issues ====
     312
     313When 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, but there's also a patch available for earlier versions [http://www.dscpl.com.au/projects/vampire/patches.html here].
     314
     315==== SELinux issues ====
     316
     317If Trac reports something like: ''Cannot get shared lock on db.lock''
     318The security context on the repository may need to be set:
     319
     320{{{
     321chcon -R -h -t httpd_sys_content_t PATH_TO_REPOSITORY
     322}}}
     323
     324See also [http://subversion.tigris.org/faq.html#reposperms]
     325
     326==== FreeBSD issues ====
     327Pay attention to the version of the installed mod_python and sqlite packages. Ports have both the new and old ones, but earlier versions of pysqlite and mod_python won't integrate as the former requires threaded support in python, and the latter requires a threadless install.
     328
     329If you compiled and installed apache2, apache wouldn´t support threads (cause it doesn´t work very well on FreeBSD). You could force thread support when running ./configure for apache, using --enable-threads, but this isn´t recommendable.
     330The best option [http://modpython.org/pipermail/mod_python/2006-September/021983.html seems to be] adding to /usr/local/apache2/bin/ennvars the line
     331
     332{{{
     333export LD_PRELOAD=/usr/lib/libc_r.so
     334}}}
     335
     336
     337==== Fedora 7 Issues ====
     338Make sure you install the 'python-sqlite2' package as it seems to be required for TracModPython but not for tracd
     339
     340
     341=== Subversion issues ===
     342
     343If 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. (The better way is to add a link to the bindings in the Python `site-packages` directory, or create a `.pth` file in that directory.)
     344
     345If this is not the case, it's possible that you're using Subversion libraries that are binary incompatible with the apache ones (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`).
     346
     347You 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. 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:
     348{{{
     349PythonInterpreter main_interpreter
     350}}}
     351This is anyway the recommended workaround for other well-known 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.
     352
     353=== Page layout issues ===
     354
     355If 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:
     356{{{
     357#!xml
     358Alias /myproject/css "/usr/share/trac/htdocs/css"
     359<Location /myproject/css>
     360    SetHandler None
     361</Location>
     362}}}
     363
     364Note: For the above configuration to have any effect it must be put after the configuration of your project root location, i.e. {{{<Location /myproject />}}}.
     365
     366Also, 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, it is probably a good idea to leave it `Off`.
     367
     368=== HTTPS issues ===
     369
     370If 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:
     371{{{
     372#!xml
     373<VirtualHost * >
     374    DocumentRoot /var/www/myproject
     375    ServerName trac.mycompany.com
     376    SetEnv HTTPS 1
     377    ....
     378</VirtualHost>
     379}}}
     380
     381
     382=== Segmentation fault with php5-mhash or other php5 modules ===
     383You 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 debian bug report [http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=411487]
     384
     385Some people also have troubles when using php5 compiled with its own 3rd party libraries instead of system libraries. Check here [http://www.djangoproject.com/documentation/modpython/#if-you-get-a-segmentation-fault]
     386
     387----
     388See also:  TracGuide, TracInstall, [wiki:TracModWSGI ModWSGI], [wiki:TracFastCgi FastCGI],  [trac:TracNginxRecipe TracNginxRecipe]