# Node thread\_pools choked

**URL:** <https://discuss.elastic.co/t/node-thread-pools-choked/387466>\
**Category:** Elasticsearch\
**Created:** [July 2, 2026, 8:04am UTC](https://discuss.elastic.co/t/node-thread-pools-choked/387466 "2026-07-02T08:04:34Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Aditya\_Teltia](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/aditya_teltia/32/122447_2.png) [@Aditya\_Teltia](https://discuss.elastic.co/u/Aditya_Teltia)\
**Post date:** [July 2, 2026, 8:04am UTC](https://discuss.elastic.co/t/node-thread-pools-choked/387466/1 "2026-07-02T08:04:34Z")

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We are using elasticsearch 7.17.6 in one our cluster.  
Recently we saw that two of the hot nodes had their thread\_pools choked. Increased Queue and rejections.

 ![image](https://us1.discourse-cdn.com/elastic/original/3X/9/1/91044f989685c3fd468caae08bde3c1af28ca10f.jpeg)

From jstack it seems that the node's CPU is occupied doing merges. Jstack shows threads are runnable however due to merges consuming CPU write, search etc thread\_pools are not able to schedule work, creating a queue and hence rejections.

Jstack link - [choked\_node\_jstack.txt · GitHub](https://gist.github.com/AdityaTeltia/4d52cfe45ea7473ed14c1d71193d8db9)

**Merges stats of this node:**

 ![image](https://us1.discourse-cdn.com/elastic/original/3X/3/4/34da811856acf0b9198e0d2713e20204033ae8dc.jpeg)

To resolve this we eventually had to restart both nodes. Could someone suggest what can/should be done to prevent this in future?

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<div class="post-metadata">

**Author:** ![covj12](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/covj12/32/147474_2.png) [@covj12](https://discuss.elastic.co/u/covj12)\
**Post date:** [July 3, 2026, 4:31am UTC](https://discuss.elastic.co/t/node-thread-pools-choked/387466/2 "2026-07-03T04:31:27Z")

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Hi, this looks like merge threads eating up CPU and starving your write/search pools. Try lowering `index.merge.scheduler.max_thread_count` to `1` on the affected indices.[Elasticsearch Guide [7.17]](https://www.elastic.co/guide/en/elasticsearch/reference/7.17/index-modules-merge.html#merge-scheduling)

```auto
PUT /my_sample_index/_settings
{
  "index.merge.scheduler.max_thread_count": 1
}

```

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<div class="post-metadata">

**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [July 3, 2026, 7:15am UTC](https://discuss.elastic.co/t/node-thread-pools-choked/387466/3 "2026-07-03T07:15:44Z")

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What type of storage are you using on the hot nodes in question? Is it local SSDs or maybe some type of networked storage?

As you are seeing a lot of throttling it is quite possible that the performance of your storage is not sufficient to support your workload. In a hot-warm architecture where the hot nodes handle all I/O intensive indexing and a lot of the querying of recent data it is vital to have high performance storage.