bitswap/httpnet: limit metric cardinality

[hsanjuan]

Currently, we label the StatusCounter metric with the hostname of the http endpoint. If there was a high number of endpoints, this would cause high cardinality for this metric.

This is a non-problem now as there are very few HTTP endpoints. This commit addresses it anyways by only labelling the metric hostnames when the Allowlist is enabled, therefore limiting labels to hostnames in the allowlist.

[codecov]

Codecov Report

Attention: Patch coverage is 59.09091% with 9 lines in your changes missing coverage. Please review.

Project coverage is 61.56%. Comparing base (8abf4db) to head (4f92c60).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
bitswap/network/httpnet/httpnet.go	14.28%	6 Missing ⚠️
bitswap/network/httpnet/metrics.go	80.00%	2 Missing and 1 partial ⚠️

@@            Coverage Diff             @@
##             main     #957      +/-   ##
==========================================
- Coverage   61.62%   61.56%   -0.07%     
==========================================
  Files         254      254              
  Lines       31409    31425      +16     
==========================================
- Hits        19357    19346      -11     
- Misses      10480    10502      +22     
- Partials     1572     1577       +5     

Files with missing lines	Coverage Δ
bitswap/network/httpnet/metrics.go	92.30% <80.00%> (-4.06%)	⬇️
bitswap/network/httpnet/httpnet.go	64.83% <14.28%> (-0.81%)	⬇️

... and 10 files with indirect coverage changes

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[hsanjuan]

I don't know why I'm feeling that I should go the extra mile and have an option to log all endpoints.

[lidel]

@hsanjuan perhaps a compromise is to have "HTTPRetrieval.Metriclist" in Kubo, and use it when HTTPRetrieval.Allowlist is not defined? This way we could track specific provider without limiting endpoints and without balooning cardinality globally.

Logging all endpoints may be used in staging/testing, we could add * (wildcard) support as explicit opt-in that one can set to enable metrics for all endpoints + log warning if someone has it set, so its not set in production by mistake.

[hsanjuan]

I have added an option for this setting. It can be bubbled later to Kubo/Rainbow when merged.