mod_backtrace gathers a backtrace after IHS child process crashes and writes it to the error log. The backtrace tells what code was running at the time of the crash and provides some information about how execution reached that point. The backtraces reported by mod_backtrace are not as useful as backtraces generated by the platform debugger from a coredump, but they provide some helpful information with little effort on the part of the administrator.
Because the backtraces generated by the platform debugger from a coredump have more information, problems can be resolved more quickly when that information is submitted to IHS support. Refer to the documentation on coredumps and backtraces in this package for more information.
(Note: The version of this module for IHS 1.3 is described here.)
Any installation of IBM HTTP Server 2.0.42.2 or above on Linux, or IBM HTTP Server 6.1 or above on z/OS, should have this module installed and activated.
In the unlikely event that coredumps cannot be written, the information from mod_backtrace will be very helpful. Even if the system and web server are configured to take coredumps, when there are multiple child process crashes a comparison of the backtraces written by mod_backtrace to the error log can be used to determine if the cause is the same. If the backtraces are the same, the cause of the crashes is expected to be the same. If the backtraces are different, the cause of the crashes may be different, and documentation should be submitted for each crash.
IBM HTTP Server 6.1 and earlier users: Copy mod_backtrace.so for your platform to the modules directory in the web server installation location (e.g., to /opt/IBMIHS/modules).
IBM HTTP Server 7.0 and later: On supported platforms, this module is provided with
the product in the modules/debug/ subdirectory.
IBM HTTP Server 6.1 and earlier users: Add the following directive after existing LoadModule directives:
LoadModule backtrace_module modules/mod_backtrace.so
IBM HTTP Server 7.0 and later: See conf/httpd.conf.default for the LoadModule directive
referencing this module from the modules/debug/ subdirectory.
Restart the server so that the updated configuration takes effect.
The module does not affect request processing in any way. It does its work after a child process crash occurs.
Comment out the LoadModule
directive added as part of the activation step.
Restart the server so that the updated configuration takes effect.