Host Metrics

[obecny]

Runtime Metrics are added on top of Host Metrics so PR is here to be able to see the differences easily:
obecny#1

[codecov]

Codecov Report

Merging #227 into master will decrease coverage by 0.01%.
The diff coverage is 94.81%.

@@            Coverage Diff             @@
##           master     #227      +/-   ##
==========================================
- Coverage   95.23%   95.21%   -0.02%     
==========================================
  Files          92      100       +8     
  Lines        4767     4979     +212     
  Branches      492      517      +25     
==========================================
+ Hits         4540     4741     +201     
- Misses        227      238      +11     

Impacted Files	Coverage Δ
packages/opentelemetry-host-metrics/.eslintrc.js	0.00% <0.00%> (ø)
...ackages/opentelemetry-host-metrics/src/stats/si.ts	88.88% <88.88%> (ø)
packages/opentelemetry-host-metrics/src/metric.ts	94.80% <94.80%> (ø)
...ges/opentelemetry-host-metrics/test/metric.test.ts	95.50% <95.50%> (ø)
packages/opentelemetry-host-metrics/src/enum.ts	100.00% <100.00%> (ø)
...ges/opentelemetry-host-metrics/src/stats/common.ts	100.00% <100.00%> (ø)
packages/opentelemetry-host-metrics/src/util.ts	100.00% <100.00%> (ø)
packages/opentelemetry-host-metrics/src/version.ts	100.00% <100.00%> (ø)
... and 6 more

[dyladan]

First pass nothing looks bad. The structure of the RCAMetrics class is a little confusing to me, but after a little reading it seems fine.

[dyladan]

Seems fine to me. The implementation of metric.ts seems more complicated than I would expect and I would be worried implementing something this complex on top of our current metrics implementation because the sdk is so incomplete and the spec is changing so much. But in general nothing seems wrong.

[mwear]

LGTM. One question about the split between host and runtime metrics. Will it be possible to collect runtime metrics without collecting host metrics? I think this is use case that we'd like to support. The reason is that the OTel collector can generate host metrics, so some people will only want to generate runtime metrics from their applications.

[mwear]

Suggested change

	#OpenTelemetry RCA Metrics for Node.js
	#OpenTelemetry Host Metrics for Node.js

[obecny]

yes the runtime metrics do not generate host metrics.