Lighttpd

= 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 --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 --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