HowToReportABug » History » Revision 4
Revision 3 (jan, 2005-08-28 21:53) → Revision 4/20 (Anonymous, 2005-09-21 09:49)
= How to report a bug =
If you find a bug in lighttpd you can help alot to find a fix for it by following some simple steps:
* [http://en.wikipedia.org/wiki/Don't_panic Don't Panic]
* if it is a crash generate a Backtrace
* if it behaves in a unexpected way prepare a strace
== Backtrace ==
A backtrace is a trace of the function which have been called before lighttpd died.
The best way to generate such a backtrace is using [http://valgrind.kde.org/ valgrind]:
{{{
$ valgrind --tool=memcheck -v --log-file=lighttpd --logfile=lighttpd --num-callers=8 lighttpd -D -f ./lighttpd.conf
}}}
valgrind does many useful things while it waits for the server to crash:
* checks for uninitialized variables
* checks for out-of-bounds access
* and many more
valgrind does not normally produce large log files and does not seem to degrade lightthpd's throughput much. Meaning, it's a very good alternative when debugging on busy servers as compared to strace.
If you can't use valgrind there is another way to generate a backtrace:
{{{
$ gdb lighttpd
(gdb) r -D -f lighttpd.conf
...
(gdb) bt
}}}
== strace ==
strace is the name of the syscall-tracer on Linux. Every Unix-like OS provides a utility to collect information about system call like open, write, close and so on.
The have different names like
* strace
* truss
* ktrace (then kdump to get output)
If strace is available it is prefered as it provides the most useful information. Execute it like:
{{{
$ strace -olighttpd.trace -tt -s 4000 lighttpd -D -f ./lighttpd.conf
}}}
It will generate a file called lighttpd.trace.
If you have a running instance of lighttpd and want to see what lighttpd is doing you can attach strace to the process:
{{{
$ strace -olighttpd.trace -tt -s 4000 -p <pidof-lighttpd>
}}}
== Memleaks ==
If you experience that lighttpd is using more than 1Gb of RAM you might have spotted a memleak. Valgrind, our valuable helper, can help you to provide the necessary information to fix it.
{{{
$ valgrind --tool=memcheck -v --log-file=lighttpd --logfile=lighttpd --num-callers=8 \
--leak-check=yes --show-reachable=yes \
lighttpd -D -f ./lighttpd.conf
}}}
Beware that this will use alot of memory and will slow down the process. You might not be able to run this on a production system with real load.
== Writing a bug report ==
If you have generated a backtrace or a syscall-trace please make sure that you can reproduce the problem. Otherwise it will be really hard for the developers to fix the problem for you.
If possible open a [http://trac.lighttpd.net/trac/newticket new ticket]
If the report contains sensitive data you might also send it directly to: mailto:jan@kneschke.de