I have an Elasticsearch cluster (version 2.3.4) with a custom app pulling data and a couchbase cluster pushing data to it (once an hour). The cluster is based on Amazon EC2 machines with the same specs and settings. After few hours one of the nodes seems to work "harder" than the others, in the monitoring plugins (KOPF, Elastic HQ) I can see the load is constantly high and once every few days the number of "Field Evictions" is raising.
While I understand this is an indication for lack of memory (which leads to high IOPs and high cpu), I wish to know why only one (specific) node is showing these symptoms in the cluster and why the load isn't spreading. If I restart the cluster, another node will show these symptoms few days after until the cluster is restarted again.
16 GB ram
Elasticsearch version 2.3.4
Thanks for the help in advance.