# WARN: o.e.t.ThreadPool - absolute clock went backwards…

**URL:** <https://discuss.elastic.co/t/warn-o-e-t-threadpool-absolute-clock-went-backwards/296320>\
**Category:** Elasticsearch\
**Created:** [February 4, 2022, 3:01pm UTC](https://discuss.elastic.co/t/warn-o-e-t-threadpool-absolute-clock-went-backwards/296320 "2022-02-04T15:01:54Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![MSN](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@MSN](https://discuss.elastic.co/u/MSN)\
**Post date:** [February 4, 2022, 3:01pm UTC](https://discuss.elastic.co/t/warn-o-e-t-threadpool-absolute-clock-went-backwards/296320/1 "2022-02-04T15:01:54Z")

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Hi,

after a fresh installation this log entry shows up on every node once a minute.

`absolute clock went backwards by [300ms/300ms] while timer thread was sleeping`

I already searched the forum and the Elasticsearch documentation but I could not find any further explanation about this error.

A google search only brings up the Elasticsearch git repository, where this error is declared.

> <https://github.com/elastic/elasticsearch/blob/master/server/src/main/java/org/elasticsearch/threadpool/ThreadPool.java>

It seems to me, that this warning has something to do with the internal thread management.  
But I could not find any hint what actually causes this warning.

NTP is configured and working on all servers.

**The environment:**  
Elasticsearch 7.16.3 / 4 Nodes  
Debian 11.2  
VMware ESXI 6.0

Maybe someone can provide a hint why this error is showing up.  
Thank you for your help!

Kind regards,  
Marc

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**Author:** ![DavidTurner](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/davidturner/32/22453_2.png) [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)\
**Post date:** [February 4, 2022, 8:42pm UTC](https://discuss.elastic.co/t/warn-o-e-t-threadpool-absolute-clock-went-backwards/296320/2 "2022-02-04T20:42:34Z")

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> [@MSN](#):
>
> Maybe someone can provide a hint why this error is showing up.

Really just what the message says: Elasticsearch read the system time, slept for a few hundred milliseconds, then read the time again and saw that the clock went backwards. NTP only typically introduces a clock discontinuity when it's unable to keep the clocks in sync any other way, so it sounds like something is wrong with your system's timekeeping.

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**Author:** ![MSN](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@MSN](https://discuss.elastic.co/u/MSN)\
**Post date:** [February 7, 2022, 8:15am UTC](https://discuss.elastic.co/t/warn-o-e-t-threadpool-absolute-clock-went-backwards/296320/3 "2022-02-07T08:15:29Z")

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Thank you for your reply. I am going to debug NTP and the system clock. As soon as I find the problem (and the solution), I am going to post it here.

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**Author:** ![MSN](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@MSN](https://discuss.elastic.co/u/MSN)\
**Post date:** [February 7, 2022, 12:46pm UTC](https://discuss.elastic.co/t/warn-o-e-t-threadpool-absolute-clock-went-backwards/296320/4 "2022-02-07T12:46:16Z")

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Thank you for your help. The Problem was indeed caused by a misconfigured upstream ntp server.

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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:** [March 7, 2022, 12:47pm UTC](https://discuss.elastic.co/t/warn-o-e-t-threadpool-absolute-clock-went-backwards/296320/5 "2022-03-07T12:47:01Z")

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