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  • wiki/pages/TracModPython

    r37567 r38412  
    1 [[TracGuideToc]]
    2 
    3 = Trac and mod_python
    4 
    5 Mod_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.
    6 Trac 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 These 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.
    9 
    10 [[PageOutline(2-3,Overview,inline)]]
    11 
    12 == Simple configuration: single project == #Simpleconfiguration
    13 
    14 If you just installed mod_python, you may have to add a line to load the module in the Apache configuration:
    15 {{{#!apache
    16 LoadModule python_module modules/mod_python.so
    17 }}}
    18 
    19 '''Note''': The exact path to the module depends on how the HTTPD installation is laid out.
    20 
    21 On Debian using apt-get:
    22 {{{#!sh
    23 apt-get install libapache2-mod-python libapache2-mod-python-doc
    24 }}}
    25 
    26 Still on Debian, after you have installed mod_python, you must enable the modules in apache2, equivalent to the above Load Module directive:
    27 {{{#!sh
    28 a2enmod python
    29 }}}
    30 
    31 On Fedora use, using yum:
    32 {{{#!sh
    33 yum install mod_python
    34 }}}
    35 
    36 You 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+.
    37 {{{#!apache
    38 <Location /mpinfo>
    39    SetHandler mod_python
    40    PythonInterpreter main_interpreter
    41    PythonHandler mod_python.testhandler
    42    Order allow,deny
    43    Allow from all
    44 </Location>
    45 }}}
    46 
    47 A simple setup of Trac on mod_python looks like this:
    48 {{{#!apache
    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
    57 </Location>
    58 }}}
    59 
    60 The 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.
    61 
    62 The options available are:
    63 {{{#!apache
    64 # For a single project
    65 PythonOption TracEnv /var/trac/myproject
    66 
    67 # For multiple projects
    68 PythonOption TracEnvParentDir /var/trac/myprojects
    69 
    70 # For the index of multiple projects
    71 PythonOption TracEnvIndexTemplate /srv/www/htdocs/trac/project_list_template.html
    72 
    73 # A space delimitted list, with a "," between key and value pairs.
    74 PythonOption TracTemplateVars key1,val1 key2,val2
    75 
    76 # Useful to get the date in the wanted order
    77 PythonOption TracLocale en_GB.UTF8
    78 
    79 # See description above       
    80 PythonOption TracUriRoot /projects/myproject
    81 }}}
    82 
    83 === Python Egg Cache
    84 
    85 Compressed 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:
    86 {{{#!apache
    87 PythonOption PYTHON_EGG_CACHE /var/trac/myprojects/egg-cache
    88 }}}
    89 
    90 Or you can uncompress the Genshi egg to resolve problems extracting from it.
    91 
    92 === Configuring Authentication
    93 
    94 See corresponding section in the [wiki:TracModWSGI#ConfiguringAuthentication] page.
    95 
    96 == Advanced Configuration
    97 
    98 === Setting the Python Egg Cache
    99 
    100 If 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.
    101 
    102 {{{#!apache
    103 <Location /projects/myproject>
    104   ...
    105   PythonOption PYTHON_EGG_CACHE /tmp
    106   ...
    107 </Location>
    108 }}}
    109 
    110 === Setting the !PythonPath
    111 
    112 If 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:
    113 {{{#!apache
    114 <Location /projects/myproject>
    115   ...
    116   PythonPath "sys.path + ['/path/to/trac']"
    117   ...
    118 </Location>
    119 }}}
    120 
    121 Be careful about using the !PythonPath directive, and ''not'' `SetEnv PYTHONPATH`, as the latter won't work.
    122 
    123 === Setting up multiple projects
    124 
    125 The Trac mod_python handler supports a configuration option similar to Subversion's `SvnParentPath`, called `TracEnvParentDir`:
    126 {{{#!apache
    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
    133 </Location>
    134 }}}
    135 
    136 When 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.
    137 
    138 If you don't want to have the subdirectory listing as your projects home page you can use a
    139 {{{#!apache
    140 <LocationMatch "/.+/">
    141 }}}
    142 
    143 This 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.
    144 
    145 You can also use the same authentication realm for all of the projects using a `<LocationMatch>` directive:
    146 {{{#!apache
    147 <LocationMatch "/projects/[^/]+/login">
    148   AuthType Basic
    149   AuthName "Trac"
    150   AuthUserFile /var/trac/.htpasswd
    151   Require valid-user
    152 </LocationMatch>
    153 }}}
    154 
    155 === Virtual Host Configuration
    156 
    157 Below is the sample configuration required to set up your Trac as a virtual server, ie when you access it at the URLs like
    158 `http://trac.mycompany.com`:
    159 
    160 {{{#!apache
    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>
    177 </VirtualHost>
    178 }}}
    179 
    180 This 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 *>`.
    184 
    185 For a virtual host that supports multiple projects replace `TracEnv /var/trac/myproject` with `TracEnvParentDir /var/trac`.
    186 
    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".
    188 
    189 == Troubleshooting
    190 
    191 If you get server error pages, you can either check the Apache error log, or enable the `PythonDebug` option:
    192 {{{#!apache
    193 <Location /projects/myproject>
    194   ...
    195   PythonDebug on
    196 </Location>
    197 }}}
    198 
    199 For multiple projects, try restarting the server as well.
    200 
    201 === Login Not Working
    202 
    203 If you've used `<Location />` directive, it will override any other directives, as well as `<Location /login>`.
    204 The workaround is to use negation expression as follows (for multi project setups):
    205 {{{#!apache
    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 /
    212 </Location>
    213 
    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 /
    220 
    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}
    225 
    226    AuthType Basic
    227    AuthName "Trac"
    228    AuthUserFile /projects/.htpasswd
    229    Require valid-user
    230 </Location>
    231 }}}
    232 
    233 === Expat-related segmentation faults === #expat
    234 
    235 This problem will most certainly hit you on Unix when using Python 2.4.
    236 In 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.
    237 As 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.
    238 
    239 === Form submission problems
    240 
    241 If 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.
    242 
    243 === Problem with virtual host configuration
    244 
    245 If 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.
    246 
    247 Using <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.
    248 
    249 === Problem with zipped egg
    250 
    251 It'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:
    252 
    253 {{{#!sh
    254 easy_install --always-unzip Trac-0.12b1.zip
    255 }}}
    256 
    257 === Using .htaccess
    258 
    259 Although 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.
    260 
    261 It 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.
    262 
    263 This also works out-of-box, with following trivial config:
    264 {{{#!apache
    265 SetHandler mod_python
    266 PythonInterpreter main_interpreter
    267 PythonHandler trac.web.modpython_frontend
    268 PythonOption TracEnv /system/path/to/this/directory
    269 PythonOption TracUriRoot /path/on/apache
    270 
    271 AuthType Basic
    272 AuthName "ProjectName"
    273 AuthUserFile /path/to/.htpasswd
    274 Require valid-user
    275 }}}
    276 
    277 The `TracUriRoot` is obviously the path you need to enter to the browser to get to Trac, eg `domain.tld/projects/trac`.
    278 
    279 === Additional .htaccess help
    280 
    281 If 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:
    282 
    283 {{{#!apache
    284 <IfModule mod_rewrite.c>
    285   RewriteEngine Off
    286 </IfModule>
    287 }}}
    288 
    289 === Platform specific issues
    290 ==== Win32 Issues
    291 
    292 If 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.
    293 
    294 ==== OS X issues
    295 
    296 When 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.
    297 
    298 ==== SELinux issues
    299 
    300 If Trac reports something like: `Cannot get shared lock on db.lock`, then the security context on the repository may need to be set:
    301 
    302 {{{#!sh
    303 chcon -R -h -t httpd_sys_content_t PATH_TO_REPOSITORY
    304 }}}
    305 
    306 See also [http://subversion.apache.org/faq.html#reposperms How do I set repository permissions correctly?]
    307 
    308 ==== FreeBSD issues
    309 
    310 The 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.
    313 
    314 Apache2 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.
    315 The best option [http://modpython.org/pipermail/mod_python/2006-September/021983.html seems to be] adding to /usr/local/apache2/bin/ennvars the line:
    316 
    317 {{{#!sh
    318 export LD_PRELOAD=/usr/lib/libc_r.so
    319 }}}
    320 
    321 ==== Fedora 7 Issues
    322 
    323 Make sure you install the 'python-sqlite2' package as it seems to be required for TracModPython, but not for tracd.
    324 
    325 === Subversion issues
    326 
    327 If 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.
    328 
    329 If 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`).
    330 
    331 You 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:
    332 {{{#!apache
    333 PythonInterpreter main_interpreter
    334 }}}
    335 
    336 This 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.
    337 
    338 === Page layout issues
    339 
    340 If 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:
    341 {{{#!apache
    342 Alias /myproject/css "/usr/share/trac/htdocs/css"
    343 <Location /myproject/css>
    344     SetHandler None
    345 </Location>
    346 }}}
    347 
    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 />}}}.
    349 
    350 Also, 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`.
    351 
    352 === HTTPS issues
    353 
    354 If 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:
    355 {{{#!apache
    356 <VirtualHost *>
    357     DocumentRoot /var/www/myproject
    358     ServerName trac.mycompany.com
    359     SetEnv HTTPS 1
    360     ....
    361 </VirtualHost>
    362 }}}
    363 
    364 === Segmentation fault with php5-mhash or other php5 modules
    365 
    366 You 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].
    367 
    368 Some 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].
    369 
    370 ----
    371 See also: TracGuide, TracInstall, [wiki:TracModWSGI ModWSGI], [wiki:TracFastCgi FastCGI], [trac:TracNginxRecipe]
Note: See TracChangeset for help on using the changeset viewer.