trac.fcgi process memory usage increases with HTTP hits

[Pistos]

# ps aux | grep trac | grep -v grep
apache   28347  1.0  1.8  51164 13816 ?        S    22:39   0:01 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi
# ps aux | grep trac | grep -v grep
apache   28347  1.0  1.8  51164 13816 ?        S    22:39   0:01 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi
# ps aux | grep trac | grep -v grep
apache   28347  1.2  1.8  51752 14420 ?        S    22:39   0:01 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi
# ps aux | grep trac | grep -v grep
apache   28347  1.4  1.9  51992 14600 ?        S    22:39   0:02 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi
# ps aux | grep trac | grep -v grep
apache   28347  1.6  1.9  52104 14760 ?        S    22:39   0:02 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi
# ps aux | grep trac | grep -v grep
apache   28347  1.7  1.9  52320 14848 ?        S    22:39   0:02 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi
# ps aux | grep trac | grep -v grep
apache   28347  1.8  1.9  52320 14856 ?        S    22:39   0:02 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi
# ps aux | grep trac | grep -v grep
apache   28347  1.8  1.9  52320 14944 ?        S    22:39   0:03 /usr/bin/python /var/www/localhost/cgi-bin/trac.fcgi

Above shows the trac.fcgi process going up in memory usage after every page refresh of a subtree in my svn repository. I only noticed this behaviour two or three weeks ago. I also have several lines in /var/log/messages indicating the Linux OOM killer killing off trac.fcgi processes when I did not notice them myself to SIGKILL them; these by-kernel kills are spread out maybe once every one or two days.

At first I thought this had to do with the svn problems that were fixed from 0.10.2 → 0.10.3, but I just upgraded, and the behaviour remains. The memory also increases when refreshing a ticket list.

I periodically upgrade the packages on my system, so that might have caused something. e.g. a Python upgrade, library upgrade, or somesuch.

This is on a Gentoo server (kernel version 2.6.17), running FastCGI (2.4.0) under Apache (2.0.58). Python version 2.4.3.

[anonymous]

Any thoughts on this issue? It remains a problem up to today, and I am having to SIGKILL trac processes at least once a day.

[Pistos]

Looks like ticket:4081 is related.

[Christian Boos]

Is the PySqlite db backend involved in this case? If yes, what versions of the bindings and the sqlite library itself are in use?

[Pistos]

Yes, it's an SQLite backend. sqlite-3.3.5, pysqlite-2.3.1.

[Pistos]

It may also be worth mentioning that this behaviour was not always the case. I've run trac in the past before without this issue. I think that was with the 0.9 series.

[Pistos]

Further data: When I only SIGTERM the process instead of SIGKILL it, it grows in memory at an alarming rate. In the area of 1-2 MB per second.

[Pistos]

I've used ​an SQLite to PostgreSQL Trac converter script to change from SQLite to PostgreSQL as my backend.

It doesn't help the problem. I am still having to SIGKILL two to five times a day (or else trac.fcgi processes consume 15-40% of my RAM). This is very annoying and inconvenient…

[Pistos]

Switching to .cgi and/or re-emerging trac with the postgres USE flag (in Gentoo) seems to have made the problem go away. So, it looks like there may be a problem with FastCGI, my FastCGI settings, and/or Trac's usage of FastCGI.

[Matthew Good]

Memory will never accumulate when using CGI since it starts a new process for each request, so the processes are very short-lived.

[esm-trac@…]

Seeing the same behavior here as well, with trac 0.10.4 running under lighttpd as a fastcgi process: a single refresh of any trac page grows the RSS of the process by anywhere from 80-256k.

This is new behavior since switching to fastcgi; on previous hosting, I was using mod_python without any noticable issues.

[Joschi]

yep, same probleme here… sometime the fcgi proccess is going crazy… will try to switch back to cgi…

[kiniry@…]

We are seeing similar problems on our ​five Tracs running on Apache 2 and OS X Leopard Server.

Additionally, approximately half a dozen FCGIs per day stop responding and consume as much CPU as they can. E.g.,

kind:BONc# peek fcgi
_www     89173  52.0  0.6   110604  27140   ??  R     4:28PM 360:08.64 /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python /Volumes/Data/web/CGI-Executables/csi-trac.fcgi
_www     11346  48.7  0.4    98716  16664   ??  R    10:41PM 353:11.91 /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python /Volumes/Data/web/CGI-Executables/csi-trac.fcgi
_www     11624  48.1  0.6   103268  23136   ??  R    11:00PM 329:11.37 /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python /Volumes/Data/web/CGI-Executables/mobius-trac.fcgi
_www     89431  45.0  0.6   101188  23080   ??  R     4:41PM 605:35.12 /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python /Volumes/Data/web/CGI-Executables/mobius-trac.fcgi
_www     18227  43.7  2.1   164836  88048   ??  R     6:42AM  79:45.42 /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python /Volumes/Data/web/CGI-Executables/mobius-trac.fcgi
_www     89167  41.8  0.8   113012  33124   ??  R     4:28PM 394:37.74 /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python /Volumes/Data/web/CGI-Executables/mobius-trac.fcgi
_www     11345  40.9  0.4    98912  16876   ??  R    10:41PM 356:56.74 /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/Python.app/Contents/MacOS/Python /Volumes/Data/web/CGI-Executables/csi-trac.fcgi

Tracing them indicates that they are all blocked on semaphores inside of Python.

I suspect that we are witnessing a concurrency issue (perhaps a livelock) related to other mod_python concurrency bugs found here. As we are running one or more FCGI processes per Trac we were hoping that switching from mod_python to FCGI would avoid these concurrency problems that have bit us in the past, but perhaps we were wrong.

Are requests shuttled through Apache to a FCGI application serialized in some fashion? How does Apache know when to spawn new FCGI processes for a given ScriptAlias? I am new to the whole FCGI API and am digging into it now, but some of these simple questions have not yet been answered in my initial reading.

Joe Kiniry

[jon]

I'm having this problem as well. Is there anything I can do to debug this and get it fixed? I'm not sure how other sites can handle using the fastcgi interface, with how the memory gets used…

[emilien@…]

Hi I used to have the same problem with FastCGI, WSGI and the HTTP server included in tracd. I'm using sqlite and lighttpd. For now I must restart Trac in a cron to avoid this memory leak. ++

[Christian Boos]

Replying to emilien@…:

… same problem with FastCGI, WSGI and the HTTP server included in tracd. I'm using sqlite and lighttpd. For now I must restart Trac in a cron to avoid this memory leak.

tracd?

If you'd like to help the project, please create a new ticket detailing your tracd configuration, the kind of repository used (svn/hg, cached or not, scoped or not), the other modules (like Genshi) and plugins you use, and then the usage patterns that make the memory grow. See #6614 for an example of the kind of information we need.

Sorry, I can't help for the FCGI issue (discussed here), but I'm highly concerned about the presence of leaks with tracd, in Trac > 0.11.1. So by any means, please help us reproduce the problem so that we could eventually fix it.

[Christian Boos]

If someone sees such a problem with recent versions of Trac (> 0.12.2), please create a new ticket with the requested information (see comment:17 just above).