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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
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
150If you don't want to have the subdirectory listing as your projects home page you can use a
151{{{#!apache
152<LocationMatch "/.+/">
153}}}
154
155This 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.
156
157You can also use the same authentication realm for all of the projects using a `<LocationMatch>` directive:
158{{{#!apache
159<LocationMatch "/projects/[^/]+/login">
160  AuthType Basic
161  AuthName "Trac"
162  AuthUserFile /var/trac/.htpasswd
163  Require valid-user
164</LocationMatch>
165}}}
166
167=== Virtual Host Configuration
168
169Below is the sample configuration required to set up your Trac as a virtual server, ie when you access it at the URLs like
170`http://trac.mycompany.com`:
171
172{{{#!apache
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, 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.
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
199'''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".
200
201== Troubleshooting
202
203If you get server error pages, you can either check the Apache error log, or enable the `PythonDebug` option:
204{{{#!apache
205<Location /projects/myproject>
206  ...
207  PythonDebug on
208</Location>
209}}}
210
211For multiple projects, try restarting the server as well.
212
213=== Login Not Working
214
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{{{#!apache
218#this one for other pages
219<Location ~ "/*(?!login)">
220   SetHandler mod_python
221   PythonHandler trac.web.modpython_frontend
222   PythonOption TracEnvParentDir /projects
223   PythonOption TracUriRoot /
224</Location>
225
226#this one for login page
227<Location ~ "/[^/]+/login">
228   SetHandler mod_python
229   PythonHandler trac.web.modpython_frontend
230   PythonOption TracEnvParentDir /projects
231   PythonOption TracUriRoot /
232
233   #remove these if you don't want to force SSL
234   RewriteEngine On 
235   RewriteCond %{HTTPS} off
236   RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
237
238   AuthType Basic
239   AuthName "Trac"
240   AuthUserFile /projects/.htpasswd
241   Require valid-user
242</Location>
243}}}
244
245=== Expat-related segmentation faults === #expat
246
247This problem will most certainly hit you on Unix when using Python 2.4.
248In 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.
249As 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.
250
251=== Form submission problems
252
253If 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.
254
255=== Problem with virtual host configuration
256
257If 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.
258
259Using <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.
260
261=== Problem with zipped egg
262
263It'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:
264
265{{{#!sh
266easy_install --always-unzip Trac-0.12b1.zip
267}}}
268
269=== Using .htaccess
270
271Although 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.
272
273It 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.
274
275This also works out-of-box, with following trivial config:
276{{{#!apache
277SetHandler mod_python
278PythonInterpreter main_interpreter
279PythonHandler trac.web.modpython_frontend
280PythonOption TracEnv /system/path/to/this/directory
281PythonOption TracUriRoot /path/on/apache
282
283AuthType Basic
284AuthName "ProjectName"
285AuthUserFile /path/to/.htpasswd
286Require valid-user
287}}}
288
289The `TracUriRoot` is obviously the path you need to enter to the browser to get to Trac, eg `domain.tld/projects/trac`.
290
291=== Additional .htaccess help
292
293If 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:
294
295{{{#!apache
296<IfModule mod_rewrite.c>
297  RewriteEngine Off
298</IfModule>
299}}}
300
301=== Platform specific issues
302==== Win32 Issues
303
304If 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.
305
306==== OS X issues
307
308When 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.
309
310==== SELinux issues
311
312If Trac reports something like: `Cannot get shared lock on db.lock`, then the security context on the repository may need to be set:
313
314{{{#!sh
315chcon -R -h -t httpd_sys_content_t PATH_TO_REPOSITORY
316}}}
317
318See also [http://subversion.apache.org/faq.html#reposperms How do I set repository permissions correctly?]
319
320==== FreeBSD issues
321
322The 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:
323 * pysqlite requires threaded support in Python
324 * mod_python requires a threadless install.
325
326Apache2 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.
327The best option [http://modpython.org/pipermail/mod_python/2006-September/021983.html seems to be] adding to /usr/local/apache2/bin/ennvars the line:
328
329{{{#!sh
330export LD_PRELOAD=/usr/lib/libc_r.so
331}}}
332
333==== Fedora 7 Issues
334
335Make sure you install the 'python-sqlite2' package as it seems to be required for TracModPython, but not for tracd.
336
337=== Subversion issues
338
339If 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.
340
341If 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`).
342
343You 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:
344{{{#!apache
345PythonInterpreter main_interpreter
346}}}
347
348This 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.
349
350=== Page layout issues
351
352If 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:
353{{{#!apache
354Alias /myproject/css "/usr/share/trac/htdocs/css"
355<Location /myproject/css>
356    SetHandler None
357</Location>
358}}}
359
360'''Note''': For the above configuration to have any effect it must be put after the configuration of your project root location, ie {{{<Location /myproject />}}}.
361
362**Note:** Do not enable python optimizations using the directive `PythonOptimize On`. When optimizations are enabled the page header/footer and documentation for macros and plugins will be hidden. An error will be raised in Trac 1.0.11 and later when optimizations are enabled.
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]
Note: See TracBrowser for help on using the repository browser.