How to close ES automatic optmization which happens at UTC 0?


My ES 2.2 got a performance hit at UTC 0 (mid night). As far as I know, it seems triggered segments merging.

In artical:

it menstioned:

Q4: stored into the Elasticsearch data, UTC is timestamp time,ElasticsearchCluster
will be at UTC 0 points, that is, Beijing time 8 points to
automatically perform optimization? How to change the parameter settings
for this time?

We do not use the Elasticsearch automatic optimization settings. Own control optimization time.

Is there anyone know how to disabel Elasticsearch automatic optimization settings?

Hi @zehong_yin,

What sort of performance hit did you experience exactly? Did indexing rate decrease? Did search latency increase? If yes, by what amount? How long did it last? What do your system metrics say for this time (CPU usage, memory usage, GC activity, network utilization...)? What was the load on your system at that time?

Yes, Elasticsearch merges segments in the background but the article gets this completely wrong. This does not happen at a specific time, but when the need arises. Read more about segment merging in the Definitive Guide. You can also read there what you can configure w.r.t. segment merging but please double and triple-check that this is really your issue (I doubt it). The quality of this article is questionable; I'd rather rely on what your system metrics tell you and then start changing configuration in a scientifically controlled manner.


If you are using time-based indices, new indices will be created at or around midnight UTC, which requires a cluster state update. Are you using time-based indices? If so, how many indices do you have per day?