Give reads priority over writes in Elasticsearch

After more monitoring using the Paramedic plugin, I noticed that I would get timeouts when my CPU would hit ~80-98% (no obvious spikes in indexing/searching traffic). I finally stumbled across a helpful thread on the Elasticsearch forum. It seems this happens when the index is doing a refresh and large merges are occurring.

Merges can be throttled at a cluster or index level and I've updated them from the indicies.store.throttle.max_bytes_per_sec from the default 20mb to 5mb. This can be done during runtime with the cluster update settings API.

PUT /_cluster/settings HTTP/1.1Host: 127.0.0.1:9200{    "persistent" : {        "indices.store.throttle.max_bytes_per_sec" : "5mb"    }}

So far Parmedic is showing a decrease in CPU usage. From an average of ~5-25% down to an average of ~1-5%. Hopefully this can help me avoid the 90%+ spikes I was having lock up my queries before, I'll report back by selecting this answer if I don't have any more problems.

As a side note, I guess I could have opted for more balanced EC2 instances (rather than memory-optimized). I think I'm happy with my current choice, but my next purchase will also take more CPU into account.