Node stats API overhead

Elastic Stack Elasticsearch
1

According to Telemetry Devices - Rally 2.10.0 documentation
It's mentioned that

Using this telemetry device will skew your results because the node-stats API triggers additional refreshes.

What "refreshes" refers to here? Index refresh?
There is no warning or information about this in the API documentation
I'm trying to understand what's the actual overhead of calling this API. For example, whether it's okay to poll this API every X ms to plot the graph of metrics reported there.
Thank you!

2

Hello,

Yes this refers to the same refreshes as the ones you can explicitly trigger from the _refresh api.

However since this PR i.e. since Elasticsearch version 7.2.0 this behavior has been notified and shouldn't be causing a refresh "storm" when hitting this api frequently.