Incorrect calculation for GC Count in Stack Monitoring

[cachedout]

Kibana version:
8c8a4a2

Elasticsearch version:
7.0 snapshot

Server OS version:
OS X

Browser version:
Version 71.0.3578.98 (Official Build) (64-bit)

Browser OS version:
OS X

Original install method (e.g. download page, yum, from source, etc.):
Source

Describe the bug:

On the GC Count graph that exists on an Elasticsearch node page inside Stack Monitoring, it appears that the metric is either being calculated incorrectly or the metric explanation and label needs to be changed.

What it appears that this metric is describing is the number of garbage collection events which have occurred during a thirty second period. However, in the graph linked below, you'll see that the number is listed as hovering between 0.1 and 0.05 events. This is impossible. You can't have a tenth of an event. :)

It does not appear that this is problem on the Elasticsearch side as a brief sanity check reveals that the metric appears to be a counter which increments upward correctly.

Steps to reproduce:

1. Create an Elaticsearch cluster which is relatively idle and enable Stack Monitoring for it.
2. Navigate to an Elasticsearch Node page inside of Stack Monitoring
3. Observe that the values in the GC Count may be < 1.

Expected behavior:

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

[elasticmachine]

Pinging @elastic/stack-monitoring

[cachedout]

cc: @pickypg for historical context to see if we can learn more about the original intention here.

[pickypg]

@tsullivan Do you remember what version we switched to /s derivative normalization?

EDIT: This is why you see 0.1 because they're 30 second buckets and there must have been 3 young GCs in the bucket.

[pickypg]

I think that we probably need to update the labels for anything using a normalized derivative.

[tsullivan]

@tsullivan Do you remember what version we switched to /s derivative normalization?

In the original repo, that PR was labeled for 6.3.0/7.0.0