hostmetricsreceiver doc updates and logging

[jrcamp]

CPU and disk metrics are not available in gopsutils on Mac when cgo is disabled
(https://github.com/shirou/gopsutil/blob/master/cpu/cpu_darwin_nocgo.go)

Errors were not logged which lead to confusion about why things weren't
working. @james-bebbington was this intentional or unintentional? It does
spam the logs a bit (every collection interval) but I don't think we can fully
rely on users checking traces for errors.

[codecov]

Codecov Report

Merging #2038 (c26052f) into master (9bf7885) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2038      +/-   ##
==========================================
- Coverage   92.23%   92.22%   -0.01%     
==========================================
  Files         280      280              
  Lines       16996    17001       +5     
==========================================
+ Hits        15676    15679       +3     
- Misses        905      906       +1     
- Partials      415      416       +1     

Impacted Files	Coverage Δ
receiver/hostmetricsreceiver/factory.go	86.84% <100.00%> (+0.17%)	⬆️
receiver/receiverhelper/scrapercontroller.go	98.93% <100.00%> (+0.04%)	⬆️
translator/internaldata/resource_to_oc.go	91.54% <0.00%> (-2.82%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9bf7885...c26052f. Read the comment docs.

[james-bebbington]

Yea I was being very conservative re logging. This change probably makes sense, given that typical scrape intervals are once every 10s-5m.

Should we add this logging to the scraper controller instead though so that errors are logged by default for all scrapers?

[james-bebbington]

Also, for the other part of this PR, should we disable the scraper (i.e. report an error if you try to use it) on Mac as well? (and add // +build !darwin to cpu_scraper_test.go since it currently fails if you run CGO_ENABLED=0 go test on Mac)

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[tigrannajaryan]

@jrcamp can you rebase?

[james-bebbington]

LGTM

Two thoughts that don't need to be addressed in this PR:

• It might be useful to make this logging optional?
• Can you create an issue for disabling the cpu scraper on darwin

[jrcamp]

LGTM

Two thoughts that don't need to be addressed in this PR:

• It might be useful to make this logging optional?

Would this be an option in ScraperControllerSettings?

• Can you create an issue for disabling the cpu scraper on darwin

Ah yeah. Created #2143. Looks like disk also has the same problem (updated readme).

[james-bebbington]

Would this be an option in ScraperControllerSettings?

I was thinking it's something developers would want to configure per scraper type rather than users needing to configure this directly, but maybe.