# Elastic runs into erratic JVM heap use
**URL:** https://discuss.elastic.co/t/elastic-runs-into-erratic-jvm-heap-use/108345
**Category:** Elasticsearch
**Created:** [November 20, 2017, 9:06am UTC](https://discuss.elastic.co/t/elastic-runs-into-erratic-jvm-heap-use/108345 "2017-11-20T09:06:17Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@raldo](https://discuss.elastic.co/u/raldo)
#### Post date: [November 20, 2017, 9:06am UTC](https://discuss.elastic.co/t/elastic-runs-into-erratic-jvm-heap-use/108345/1 "2017-11-20T09:06:17Z")
We are using Elastic 5.6.3, 3 nodes with 64gb mem (2 physical and one VM on CentOS) and .net core services which query and write to index.
Our platform is a classifieds site with many search facets; we are using Datadog to monitor various health signals. The most pressing concern atm is that the JVM heap use across all the nodes would be very stable for about 4 hours and then garbage collection would become very erratic and more frequent. This would lead to a slower query time and less stable cluster.
We are recycling the IIS service every 4 hours which then results in normal garbage collection patterns for the next 4 hours. There are no other backend services querying the cluster.
The question is; what is the best way and most obvious metrics to measure to understand why JVM heap use is normal for hours and then slowly starts to degrade?
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [December 18, 2017, 9:06am UTC](https://discuss.elastic.co/t/elastic-runs-into-erratic-jvm-heap-use/108345/2 "2017-12-18T09:06:21Z")
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