# ES JVM use ZGC, esrally can't work

**URL:** <https://discuss.elastic.co/t/es-jvm-use-zgc-esrally-cant-work/246253>\
**Category:** Elasticsearch\
**Tags:** rally\
**Created:** [August 25, 2020, 8:48am UTC](https://discuss.elastic.co/t/es-jvm-use-zgc-esrally-cant-work/246253 "2020-08-25T08:48:58Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Zhayhp](https://avatars.discourse-cdn.com/v4/letter/z/59ef9b/32.png) [@Zhayhp](https://discuss.elastic.co/u/Zhayhp)\
**Post date:** [August 25, 2020, 8:48am UTC](https://discuss.elastic.co/t/es-jvm-use-zgc-esrally-cant-work/246253/1 "2020-08-25T08:48:58Z")

</div>

There is an error in the rally code (jvm\_stats) when I set the ES Jvm use ZGC.

rally.log

```auto
Traceback (most recent call last):

  File "/usr/local/python38/lib/python3.8/site-packages/esrally/actor.py", line 85, in guard
    return f(self, msg, sender)

  File "/usr/local/python38/lib/python3.8/site-packages/esrally/driver/driver.py", line 222, in receiveMsg_StartBenchmark
    self.coordinator.start_benchmark()

  File "/usr/local/python38/lib/python3.8/site-packages/esrally/driver/driver.py", line 460, in start_benchmark
    self.telemetry.on_benchmark_start()

  File "/usr/local/python38/lib/python3.8/site-packages/esrally/telemetry.py", line 76, in on_benchmark_start
    device.on_benchmark_start()

  File "/usr/local/python38/lib/python3.8/site-packages/esrally/telemetry.py", line 977, in on_benchmark_start
    self.jvm_stats_per_node = self.jvm_stats()

  File "/usr/local/python38/lib/python3.8/site-packages/esrally/telemetry.py", line 1027, in jvm_stats
    old_gen_collection_time = gc["old"]["collection_time_in_millis"]

KeyError: 'old'

```

The ES reture gc data is  
`"gc":{"collectors":{"ZGC":{"collection_count":96,"collection_time_in_millis":352}}}`

---

<div class="post-metadata">

**Author:** ![Dale\_McDiarmid](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dale_mcdiarmid/32/74184_2.png) [@Dale\_McDiarmid](https://discuss.elastic.co/u/Dale_McDiarmid)\
**Post date:** [August 25, 2020, 10:29am UTC](https://discuss.elastic.co/t/es-jvm-use-zgc-esrally-cant-work/246253/2 "2020-08-25T10:29:56Z")

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Hi  
Whilst we [don't support ZGC](https://www.elastic.co/support/matrix#matrix_jvm) in Elasticsearch, Rally should be robust and fail gracefully when it is unable to collect such additional stats. Given this requires code changes please follow this bug report [here](https://github.com/elastic/rally/issues/1052).

Thanks

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<div class="post-metadata">

**Author:** ![dominique.bejean](https://avatars.discourse-cdn.com/v4/letter/d/dc4da7/32.png) [@dominique.bejean](https://discuss.elastic.co/u/dominique.bejean)\
**Post date:** [August 25, 2020, 2:09pm UTC](https://discuss.elastic.co/t/es-jvm-use-zgc-esrally-cant-work/246253/3 "2020-08-25T14:09:38Z")

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Hi,

With ZGC, /\_nodes/stats entry point do not report anymore old, young gc information for the jvm.

Enabling ZGC is experimental and rally do not support this for the time being.

Dominique

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [September 22, 2020, 2:09pm UTC](https://discuss.elastic.co/t/es-jvm-use-zgc-esrally-cant-work/246253/4 "2020-09-22T14:09:42Z")

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