# Why heap used of a new elasticsearch cluster with no document can be 26% ? What memory is Used for?
**URL:** https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455
**Category:** Elasticsearch
**Tags:** elastic-stack-monitoring
**Created:** [October 28, 2019, 12:16pm UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455 "2019-10-28T12:16:53Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 28, 2019, 12:16pm UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/1 "2019-10-28T12:16:53Z")
unit is M and I use \_nodes/stats API
heap\_used\_in\_bytes = 4298.34
heap\_used\_percent = 26
heap\_max\_in\_bytes = 16067.875
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 28, 2019, 12:22pm UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/2 "2019-10-28T12:22:01Z")
What the memory is used for ? Something else possible need to be loaded is 0.0
segment\_memory\_in\_bytes = 0.0
terms\_memory\_in\_bytes = 0.0
stored\_fields\_memory\_in\_bytes = 0.0
term\_vectors\_memory\_in\_bytes = 0.0
norms\_memory\_in\_bytes = 0.0
points\_memory\_in\_bytes = 0.0
doc\_values\_memory\_in\_bytes = 0.0
index\_writer\_memory\_in\_bytes = 0.0
request\_cache = 0.0
query\_cache = 0.0
fielddata = 0.0
---
### Author:  [@Mike\_Place](https://discuss.elastic.co/u/Mike_Place)
#### Post date: [October 28, 2019, 2:06pm UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/3 "2019-10-28T14:06:50Z")
Hi @panxuelin
Have you indexed any documents into this cluster?
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 12:58am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/4 "2019-10-29T00:58:40Z")
It's a new cluster with no document
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### Author:  [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [October 29, 2019, 4:39am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/5 "2019-10-29T04:39:44Z")
What does `_cat/nodes?v` and `_cat/indices?v` show?
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 6:17am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/6 "2019-10-29T06:17:01Z")
[root@node4 ~]# curl localhost:9200/\_cat/nodes?v
ip heap.percent ram.percent cpu load\_1m load\_5m load\_15m node.role master name
28.28.0.4 26 16 0 0.06 0.07 0.05 mdi \* node4
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 6:17am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/7 "2019-10-29T06:17:46Z")
It‘s same with \_node/stats API
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 6:34am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/8 "2019-10-29T06:34:00Z")
Are there anybody encounter the same problem ? Just create a new cluster and use python client to monitor. Heap\_used\_percent is alway high , from 12 percent to 26 percent
self.es\_rest = Elasticsearch(
server,
timeout=int(self.timeout),
max\_retries=int(self.max\_retries),
retry\_on\_timeout=True)
stats\_response = self.es\_rest.nodes.stats()
---
### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [October 29, 2019, 6:39am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/9 "2019-10-29T06:39:15Z")
There are a lot of things that will use heap apart from data. Elasticsearch itself use a certain amount and every request to the cluster is likely to use a bit more. This includes requests not directly related to data. If there is no data in the cluster heap usage typically grows slowly though, but it will grow over time as garbage collection usually only kicks in when the heap is 75% full.
The best way to see what the static overhead is is to restart the node and measure it before any requests have been served.
---
### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 6:57am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/10 "2019-10-29T06:57:13Z")
My cluster is a new cluster with no other request cache. I try to restart elasticsearch and send the first request after 5min. The result show that memory size of
query\_cache, fielddata and segments is 0. Are there any api to show what elasticsearch use 12% heap memory for?
"query\_cache" : {
"memory\_size\_in\_bytes" : 0,
"total\_count" : 0,
"hit\_count" : 0,
"miss\_count" : 0,
"cache\_size" : 0,
"cache\_count" : 0,
"evictions" : 0
},
"fielddata" : {
"memory\_size\_in\_bytes" : 0,
"evictions" : 0
},
"completion" : {
"size\_in\_bytes" : 0
},
"segments" : {
"count" : 0,
"memory\_in\_bytes" : 0,
"terms\_memory\_in\_bytes" : 0,
"stored\_fields\_memory\_in\_bytes" : 0,
"term\_vectors\_memory\_in\_bytes" : 0,
"norms\_memory\_in\_bytes" : 0,
"points\_memory\_in\_bytes" : 0,
"doc\_values\_memory\_in\_bytes" : 0,
"index\_writer\_memory\_in\_bytes" : 0,
"version\_map\_memory\_in\_bytes" : 0,
"fixed\_bit\_set\_memory\_in\_bytes" : 0,
"max\_unsafe\_auto\_id\_timestamp" : -9223372036854775808,
"file\_sizes" : { }
}
"jvm" : {
"timestamp" : 1572331615124,
"uptime\_in\_millis" : 107789,
"mem" : {
"heap\_used\_in\_bytes" : 2121881128,
"heap\_used\_percent" : 12,
"heap\_committed\_in\_bytes" : 16848388096,
"heap\_max\_in\_bytes" : 16848388096,
"non\_heap\_used\_in\_bytes" : 72268584,
"non\_heap\_committed\_in\_bytes" : 79777792,
---
### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [October 29, 2019, 7:00am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/11 "2019-10-29T07:00:57Z")
That looks high for being a completely empty cluster. Even through you do not have any data in the cluster, have you uploaded anything else, e.g. index templates, synonyms etc? Do you have any plugins installed that might use a lot of heap? Do you have any non-default settings in your elasticsearch.yml file?
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 7:04am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/12 "2019-10-29T07:04:48Z")
Completly new Cluster with no plugin, document. Just modify the elasticsearch.yml
http.cors.enabled: true
http.cors.allow-origin: "\*"
thread\_pool.write.size: 32
thread\_pool.search.size: 64
thread\_pool.get.size: 32
thread\_pool.write.queue\_size: 100
thread\_pool.search.queue\_size: 3000
thread\_pool.get.queue\_size: 2000
http.max\_content\_length: 500mb
network.publish\_host: 28.28.0.4
---
### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [October 29, 2019, 7:53am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/13 "2019-10-29T07:53:49Z")
Does the size change if you comment those out and go back to defaults?
---
### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [October 29, 2019, 8:01am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/14 "2019-10-29T08:01:21Z")
How did you arrive at these custom settings? Why are they required? Elasticsearch is not designed to handle very large documents, so. The large http request size is a bit concerning.
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 8:11am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/15 "2019-10-29T08:11:42Z")
http.max\_content\_length is used to limite bulk size and our document is small. Just avoid extreme case.
I think these custom settings have nothing to do with heap used of cluster now. I just send \_nodes/stats request
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### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [October 29, 2019, 8:57am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/16 "2019-10-29T08:57:56Z")
Did going with defaults make any difference?
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 9:09am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/17 "2019-10-29T09:09:31Z")
No ,same with last time
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### Author:  [@Mike\_Place](https://discuss.elastic.co/u/Mike_Place)
#### Post date: [October 29, 2019, 11:13am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/18 "2019-10-29T11:13:57Z")
> [@panxuelin](#):
>
> http.cors.enabled: true
> http.cors.allow-origin: "\*"
>
> thread\_pool.write.size: 32
> thread\_pool.search.size: 64
> thread\_pool.get.size: 32
> thread\_pool.write.queue\_size: 100
> thread\_pool.search.queue\_size: 3000
> thread\_pool.get.queue\_size: 2000
>
> http.max\_content\_length: 500mb
> network.publish\_host: 28.28.0.4
Another way to poke around for answers here might be to take some heap dumps and see if anything obvious stands out. Below I've recorded a brief screencast of doing this using [VisualVM](https://visualvm.github.io).
**Warning: mucking about with heap dumps and profilers in a production cluster is at your own risk!**
**Edit:** That upload resized the gif so it's too small to read. Try this: [https://giphy.com/gifs/U7PeHMxToTLIRMtw2D](https://giphy.com/gifs/U7PeHMxToTLIRMtw2D)
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### Author:  [@panxuelin](https://discuss.elastic.co/u/panxuelin)
#### Post date: [October 29, 2019, 11:35am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/19 "2019-10-29T11:35:47Z")
Thank you so much. I make a try. But video is Blurry, can you repeat a clear one
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [November 26, 2019, 11:36am UTC](https://discuss.elastic.co/t/why-heap-used-of-a-new-elasticsearch-cluster-with-no-document-can-be-26-what-memory-is-used-for/205455/20 "2019-11-26T11:36:20Z")
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