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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
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.
9
10[[PageOutline(2-3,Overview,inline)]]
11
12== Simple configuration: single project == #Simpleconfiguration
13
14If you just installed mod_python, you may have to add a line to load the module in the Apache configuration:
15{{{#!apache
16LoadModule 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
21On Debian using apt-get:
22{{{#!sh
23apt-get install libapache2-mod-python libapache2-mod-python-doc
24}}}
25
26Still on Debian, after you have installed mod_python, you must enable the modules in apache2, equivalent to the above Load Module directive:
27{{{#!sh
28a2enmod python
29}}}
30
31On Fedora use, using yum:
32{{{#!sh
33yum install mod_python
34}}}
35
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+.
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
47A 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
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.
61
62The options available are:
63{{{#!apache
64# For a single project
65PythonOption TracEnv /var/trac/myproject
66
67# For multiple projects
68PythonOption TracEnvParentDir /var/trac/myprojects
69
70# For the index of multiple projects
71PythonOption TracEnvIndexTemplate /srv/www/htdocs/trac/project_list_template.html
72
73# A space delimitted list, with a "," between key and value pairs.
74PythonOption TracTemplateVars key1,val1 key2,val2
75
76# Useful to get the date in the wanted order
77PythonOption TracLocale en_GB.UTF8
78
79# See description above       
80PythonOption TracUriRoot /projects/myproject
81}}}
82
83=== Python Egg Cache
84
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:
86{{{#!apache
87PythonOption PYTHON_EGG_CACHE /var/trac/myprojects/egg-cache
88}}}
89
90Or you can uncompress the Genshi egg to resolve problems extracting from it.
91
92=== Configuring Authentication
93
94See corresponding section in the [wiki:TracModWSGI#ConfiguringAuthentication] page.
95
96== Advanced Configuration
97
98=== Setting the Python Egg Cache
99
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.
101
102{{{#!apache
103<Location /projects/myproject>
104  ...
105  PythonOption PYTHON_EGG_CACHE /tmp 
106  ...
107</Location>
108}}}
109
110=== Setting the !PythonPath
111
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:
113{{{#!apache
114<Location /projects/myproject>
115  ...
116  PythonPath "sys.path + ['/path/to/trac']"
117  ...
118</Location>
119}}}
120
121Be careful about using the !PythonPath directive, and ''not'' `SetEnv PYTHONPATH`, as the latter won't work.
122
123=== Setting up multiple projects
124
125The 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
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.
137
138If you don't want to have the subdirectory listing as your projects home page you can use a
139{{{#!apache
140<LocationMatch "/.+/">
141}}}
142
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.
144
145You 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
157Below 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
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 *>`.
184
185For 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
191If 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
199For multiple projects, try restarting the server as well.
200
201=== Login Not Working
202
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):
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
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.
238
239=== Form submission problems
240
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.
242
243=== Problem with virtual host configuration
244
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.
246
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.
248
249=== Problem with zipped egg
250
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:
252
253{{{#!sh
254easy_install --always-unzip Trac-0.12b1.zip
255}}}
256
257=== Using .htaccess
258
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.
260
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.
262
263This also works out-of-box, with following trivial config:
264{{{#!apache
265SetHandler mod_python
266PythonInterpreter main_interpreter
267PythonHandler trac.web.modpython_frontend
268PythonOption TracEnv /system/path/to/this/directory
269PythonOption TracUriRoot /path/on/apache
270
271AuthType Basic
272AuthName "ProjectName"
273AuthUserFile /path/to/.htpasswd
274Require valid-user
275}}}
276
277The `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
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:
282
283{{{#!apache
284<IfModule mod_rewrite.c>
285  RewriteEngine Off
286</IfModule>
287}}}
288
289=== Platform specific issues
290==== Win32 Issues
291
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.
293
294==== OS X issues
295
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.
297
298==== SELinux issues
299
300If 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
303chcon -R -h -t httpd_sys_content_t PATH_TO_REPOSITORY
304}}}
305
306See also [http://subversion.apache.org/faq.html#reposperms How do I set repository permissions correctly?]
307
308==== FreeBSD issues
309
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.
313
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:
316
317{{{#!sh
318export LD_PRELOAD=/usr/lib/libc_r.so
319}}}
320
321==== Fedora 7 Issues
322
323Make sure you install the 'python-sqlite2' package as it seems to be required for TracModPython, but not for tracd.
324
325=== Subversion issues
326
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.
328
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`).
330
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:
332{{{#!apache
333PythonInterpreter main_interpreter
334}}}
335
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.
337
338=== Page layout issues
339
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:
341{{{#!apache
342Alias /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
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`.
351
352=== HTTPS issues
353
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:
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
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].
367
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].
369
370----
371See also: TracGuide, TracInstall, [wiki:TracModWSGI ModWSGI], [wiki:TracFastCgi FastCGI], [trac:TracNginxRecipe]
Note: See TracBrowser for help on using the repository browser.