# 100% heap usage during indexing

**URL:** <https://discuss.elastic.co/t/100-heap-usage-during-indexing/20565>\
**Category:** Elasticsearch\
**Created:** [November 4, 2014, 6:27pm UTC](https://discuss.elastic.co/t/100-heap-usage-during-indexing/20565 "2014-11-04T18:27:08Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Evan\_Kerstiens](https://avatars.discourse-cdn.com/v4/letter/e/f04885/32.png) [@Evan\_Kerstiens](https://discuss.elastic.co/u/Evan_Kerstiens)\
**Post date:** [November 4, 2014, 6:27pm UTC](https://discuss.elastic.co/t/100-heap-usage-during-indexing/20565/1 "2014-11-04T18:27:08Z")

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Hey guys,

I have a few questions:

1. I was wondering if anyone knows how to limit how much memory  
elasticsearch uses while indexing.  
During our loading jobs, typically we only see 60-70% heap usage before the  
garbage collector  
kicks in, but recently we saw some large traffic while loading and the heap  
went to 100%.  
After that everything became unresponsive each time the garbage collector  
would run. As an example  
it spent a full minute running to clear only 46.5mb. Eventually we had to  
restart ES.

We use mostly default settings for ES. We only changed the cluster and  
node names, and  
changed the index and search threadpools to be of type cached. Is the  
unlimited threadpool  
for indexing to blame, or are we missing a setting somewhere? I should  
mention we are currently  
using v1.0.0 ES.

1. Also, at one point we had a cluster failure (still investigating the  
cause), and after  
rebalancing the speed was very slow, often resulting in timeouts. When the  
cluster returned,  
the speed went back to normal. Is this just an inevitable consequence of  
losing a cluster,  
or should speeds be comparable to before the failure after rebalance?

2. My lead also wanted me to ask about RAM allocation. We read that you  
should not allocate  
more than 50% of the available RAM to ES because Lucene needs the rest for  
filesystem caching.  
Will this show up as used RAM in top? He said he didn't see the rest of  
the RAM being used.

Thanks in advance guys. We are new to ElasticSearch, and we thought we  
would ask some advice  
before crashing the site again.

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [July 6, 2017, 12:52am UTC](https://discuss.elastic.co/t/100-heap-usage-during-indexing/20565/2 "2017-07-06T00:52:11Z")

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