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diff --git a/doc/troubleshoot.html b/doc/troubleshoot.html index a8855fd..0f0c7fc 100644 --- a/doc/troubleshoot.html +++ b/doc/troubleshoot.html @@ -102,13 +102,63 @@ comes without any guarantees, include no guarantee on confidentiality [aka "we don't want to be sued for work were are not even paid for ;)]. <b>So if you submit debug logs, do so at your sole risk</b>. By submitting them, you accept this policy. +<p><b>Segmentation Faults</b> +<p>Rsyslog has a very rapid development process, complex capabilities and now gradually gets +more and more exposure. While we are happy about this, it also has some bad effects: some +deployment scenarios have probably never been tested and it may be impossible to test +them for the development team because of resources needed. So while we try to avoid this, +you may see a serious problem during deployments in demanding, non-standard, environments +(hopefully not with a stable version, but chances are good you'll run into troubles with +the development versions). +<p>Active support from the user base is very important to help us track down those things. +Most often, serious problems are the result of some memory misadressing. During development, +we routinely use valgrind, a very well and capable memory debugger. This helps us to create +pretty clean code. But valgrind can not detect everything, most importantly not code pathes +that are never executed. So of most use for us is information about aborts and abort locations. +<p>Unforutnately, faults rooted in adressing errors typically show up only later, so the +actual abort location is in an unrelated spot. To help track down the original spot, +<a href="http://www.gnu.org/software/hello/manual/libc/Heap-Consistency-Checking.html">libc +later than 5.4.23 offers support</a> for finding, and possible temporary relief from it, +by means of the MALLOC_CHECK_ environment variable. Setting it to 2 is a useful troubleshooting +aid for us. It will make the program abort as soon as the check routines detect anything +suspicious (unfortunately, this may still not be the root cause, but hopefully closer to it). +Setting it to 0 may even make some problems disappear (but it will NOT fix them!). +With functionality comes cost, and so exporting MALLOC_CHECK_ without need comes at +a performance penalty. However, we strongly recommend adding this instrumentation to your +test environment should you see any serious problems. Chances are good it will help us +interpret a dump better, and thus be able to quicker craft a fix. +<p>In order to get useful information, we need some backtrace of the abort. First, you need +to make sure that a core file is created. Under Fedora, for example, that means you need +to have an "ulimit -c unlimited" in place. +<p>Now let's assume you got a core file (e.g. in /core.1234). So what to do next? Sending a +core file to us is most often pointless - we need to have the exact same system configuration in +order to interpret it correctly. Obviously, chances are extremely slim for this to be. So we would +appreciate if you could extract the most important information. This is done as follows: +<ul> +<li>$gdb /path/to/rsyslogd +<li>$info thread +<li>you'll see a number of threads (in the range 0 to n with n being the highest number). For + <b>each</b> of them, do the following (let's assume that i is the thread number): + <ul> + <li>$ thread i (e.g. thread 0, thread 1, ...) + <li>$bt + </ul> +<li>then you can quit gdb with "$q" +</ul> +<p>Then please send all information that gdb spit out to the development team. It is best to first +ask on the forum or mailing list on how to do that. The developers will keep in contact with you +and, I fear, will probably ask for other things as well ;) +<p>Note that we strive for highest reliability of the engine even in unusual deployment scenarios. +Unfortunately, this is hard to achieve, especially with limited resources. So we are depending on +cooperation from users. This is your chance to make a big contribution to the project without the +need to program or do anything else except get a problem solved ;) <p>[<a href="manual.html">manual index</a>] [<a href="http://www.rsyslog.com/">rsyslog site</a>]</p> <p><font size="2">This documentation is part of the <a href="http://www.rsyslog.com/">rsyslog</a> project.<br> -Copyright © 2008 by <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a> and +Copyright © 2008-2010 by <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a> and <a href="http://www.adiscon.com/">Adiscon</a>. Released under the GNU GPL -version 2 or higher.</font></p> +version 3 or higher.</font></p> </body> </html> |