ArangoDB 2.6.8: Latest Updates and Enhancements

The release ArangoDB 2.6.8 fixes a memory access bug on ARM. So for your pet project on a Raspberry Pi you need to change the CPU alignment setting to allow unaligned memory access.

There is no need to update to 2.6.8 for other distributions.

ARM only

The ArangoDB packages for ARM require the kernel to allow unaligned memory access. How the kernel handles unaligned memory access is configurable at runtime by checking and adjusting the contents /proc/cpu/alignment.

In order to operate on ARM, ArangoDB requires the bit 1 to be set. This will make the kernel trap and adjust unaligned memory accesses. If this bit is not set, the kernel may send a SIGBUS signal to ArangoDB and terminate it.

To set bit 1 in /proc/cpu/alignment use the following command as a privileged user (e.g. root):

echo "2" > /proc/cpu/alignment

Note that this setting affects all user processes and not just ArangoDB. Setting the alignment with the above command will also not make the setting permanent, so it will be lost after a restart of the system. In order to make the setting permanent, it should be executed during system startup or before starting arangod.

The ArangoDB start/stop scripts do not adjust the alignment setting, but rely on the environment to have the correct alignment setting already. The reason for this is that the alignment settings also affect all other user processes (which ArangoDB is not aware of) and thus may have side-effects outside of ArangoDB. It is therefore more reasonable to have the system administrator carry out the change.