Prevent mysql process being killed by OOM killer
RHEL7 uses systemd.
Using the OOMScoreAdjust as follows:

sudo systemctl edit mysqld.service


Note: I'm not sure of the exact service name

Add the following text:

[Service]
OOMScoreAdjust=-1000


restart with:

systemctl restart mysqld.service


Check by looking at the score:

cat /proc/$(pidof mysqld)/oom_score_adj