This post explains how to debug MySQL Cluster 7.1, installed using the RPM packages, using gdb on a Linux box (Red Hat, Oracle Enterprise Linux, CentOS, ..).

When a data node crashes lots of information goes into the error log, trace files and out log. However, it makes sometimes sense when you can repeat the crash, to run the data node in debug mode, or using gdb.

First, using RPMs and a Linux distribution, make sure you have the ‘debuginfo’ package installed. For example, for Red Hat or Oracle Enterprise Linux on a 64-bit machine, this package would be called: MySQL-Cluster-gpl-debuginfo-7.1.15-1.rhel5.x86_64.rpm.

Create a file with the following commands, we will name it ndbd.gdb:

set pagination off
set logging overwrite on
set logging file ndbd_gdb_backtrace.txt
set logging on
run --foreground -c <YourMGM:1186> --ndb-nodeid=<YourID>
thread apply all bt
set logging off

Note line 5: pass the options to ‘run’ which you usually pass when starting ndbd, but leave the --foreground option. Note line 3: you can save of course the logging file wherever you want to.

Then all you need to do is run gdb with the commands file and the ndbd binary you just created:

$ gdb /usr/sbin/ndbd -x ndbd.gdb

A full backtrace of threads will be available in the logging file when ndbd crashes. This you can then upload when reporting bugs.

There are probably more options and things you can do, please post them in the comments!