Minor config
Note, that ES 6.x requires max_map_count to be at least 262144
This can be set by setting sysctl -w vm.max_map_count=262144 or by setting discovery.type=single-node
To set this on gitlab-ci env, change the service to this:
services:
- name: leifcr/elasticsearch
alias: elasticsearch
command: [ "bin/elasticsearch", "-Ediscovery.type=single-node" ]