Tuning Elasticsearch: The Ideal Java Heap Size

In the journey for peak performance and lowest possible cost, the Elasticsearch Java heap size plays a significant role. What is the right value for ES_HEAP_SIZE? Is there a right number to always use? In this article we ignore all the disinformation and get to the optimal answer using benchmarks.

Elasticsearch is a complex distributed system, and as your dataset and query volume grow, the cost of operating a cluster grows as well. To help reduce the operating cost, Elasticsearch provides you with many different levers to tune the performance for each cluster.

This is the first in a series of articles about tuning your Elasticsearch cluster. In this article, we start discussing one of the two most common levers available for tuning a single node in a cluster: heap size and garbage collection algorithm. Those are also the ones with most confusion and even disinformation spread on online forums.

This series is being written after many years of consulting many customers world-wide on a variety of use-cases, cluster sizes and hardware specs - ever since Elasticsearch 0.11 was released 11 years ago. We helped many projects succeed and while every engagement required attention to different details, eventually the basics are all the same and we always start at the same point.

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