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HowToReportABug » History » Revision 3

Revision 2 (jan, 2005-08-22 16:18) → Revision 3/19 (jan, 2005-08-28 21:53)

= 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 --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 

 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 --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