# Different thread priorities for indexing vs. searching?

**URL:** <https://discuss.elastic.co/t/different-thread-priorities-for-indexing-vs-searching/33090>\
**Category:** Elasticsearch\
**Created:** [October 27, 2015, 4:33pm UTC](https://discuss.elastic.co/t/different-thread-priorities-for-indexing-vs-searching/33090 "2015-10-27T16:33:19Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![otisg](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/otisg/32/492_2.png) [@otisg](https://discuss.elastic.co/u/otisg)\
**Post date:** [October 27, 2015, 4:33pm UTC](https://discuss.elastic.co/t/different-thread-priorities-for-indexing-vs-searching/33090/1 "2015-10-27T16:33:19Z")

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Hi,

ES has different thread pools for indexing, searching, etc. Is it possible to tell ES to set different priority on indexing vs. search requests? I didn't see a way to do that.

Wouldn't that be very valuable, especially for the popular logging use case?

## Thanks, Otis

Monitoring - Log Management - Alerting - Anomaly Detection  
Elasticsearch Consulting - Support - Training - [http://sematext.com/](http://sematext.com/)

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**Author:** ![jprante](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jprante/32/44941_2.png) [@jprante](https://discuss.elastic.co/u/jprante)\
**Post date:** [October 27, 2015, 5:54pm UTC](https://discuss.elastic.co/t/different-thread-priorities-for-indexing-vs-searching/33090/2 "2015-10-27T17:54:37Z")

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A good idea in general, but not a good idea on the JVM.

- you have to be `root` to raise priority of threads (on Linux at least), so the question is if lowering thread priorities is of any benefit
- lowering thread priorities make threads always run slower (see UNIX 'nice')
- you need to instruct ES users how to map Java threads to OS native threads on the specific hardware, which is flaky when using `-XX:ThreadPriorityPolicy` e.g. by not-so-well documented JVM flags like

```auto
-XX:ThreadPriorityPolicy=42
-XX:JavaPriority10_To_OSPriority=0
-XX:JavaPriority9_To_OSPriority=1
-XX:JavaPriority8_To_OSPriority=2
-XX:JavaPriority7_To_OSPriority=3
-XX:JavaPriority6_To_OSPriority=4
-XX:JavaPriority5_To_OSPriority=5
-XX:JavaPriority4_To_OSPriority=6
-XX:JavaPriority3_To_OSPriority=7
-XX:JavaPriority2_To_OSPriority=8
-XX:JavaPriority1_To_OSPriority=9

```

- thread behavior varies from JDK to JDK version, e.g. on Solaris, see [https://blogs.oracle.com/dave/entry/java\_thread\_priority\_revisted\_in](https://blogs.oracle.com/dave/entry/java_thread_priority_revisted_in)
- thread management depends also on the JVM implementation
- I'm not familiar with Windows but I bet it's a totally different story
- from OS to OS, threads would behave differently, which opens a can of worms

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**Author:** ![otisg](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/otisg/32/492_2.png) [@otisg](https://discuss.elastic.co/u/otisg)\
**Post date:** [October 28, 2015, 12:38am UTC](https://discuss.elastic.co/t/different-thread-priorities-for-indexing-vs-searching/33090/3 "2015-10-28T00:38:00Z")

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Hi,

Hmmm, I think we are out of sync. I'm not referring to process priorities and "nice". I'm referring to Thread class in Java:  
[http://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html](http://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html)  
"Every thread has a priority. Threads with higher priority are executed in preference to threads with lower priority...."

And here are the 3 priorities:  
[http://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html#field\_summary](http://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html#field_summary)

So this is a Java-level thing (and maybe it translates to OS-level processes or threads, which must be different on different OSes, but that's "not my concern" here) and I'm thinking it would be useful to be able to configure:  
index pool priority: min  
search pool priority: max  
etc.

Wouldn't that be helpful and super easy to implement?

## Otis

Monitoring - Log Management - Alerting - Anomaly Detection  
Elasticsearch Consulting - Support - Training - [http://sematext.com/](http://sematext.com/)

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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 5, 2017, 11:42pm UTC](https://discuss.elastic.co/t/different-thread-priorities-for-indexing-vs-searching/33090/4 "2017-07-05T23:42:17Z")

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