We're using 0.17.8 in production. About a week ago I changed from
storing our web sessions in our DB to storing them in ElasticSearch.
We have about 50m sessions, stored in an index with 1 primary shard and
1 replica, which amounts to about 11GB of data.
All was working well, then today we suddenly had 3 minutes of requests
to the session index timing out (>30 seconds).
The node with the primary shard had high loads and was in the process of
doing a merge which lasted about 5 minutes.
Is there anything I should tweak to make these merges lighter?