Update module github.com/prometheus/common to v0.62.0 and fix tests

[dashpole]

Supersedes #6171

The update to prometheus/common changes the default escaping scheme to NoEscaping. Use of underscores vs original UTF-8 is still determined by content negotiation.

[dashpole]

@ywwg I found one potential breaking change with the prometheus/common underscore escaping logic. The current behavior OTel-Go implemented handles colliding keys by concatenating the values with a ;.

The diff from the unit test is:

-foo_total{A_B="Q",C_D="Y",C_D="Z",otel_scope_name="testmeter",otel_scope_version="v0.1.0"} 24.3
+foo_total{A_B="Q",C_D="Y;Z",otel_scope_name="testmeter",otel_scope_version="v0.1.0"} 24.3

The unit test does this:

opt := otelmetric.WithAttributes(
    // exact match, value should be overwritten
    attribute.Key("A.B").String("X"),
    attribute.Key("A.B").String("Q"),

    // unintended match due to sanitization, values should be concatenated
    attribute.Key("C.D").String("Y"),
    attribute.Key("C/D").String("Z"),
)

It seems like there are a few paths forward (cc @ArthurSens):

1. Accept this change as-is. If users have collisions, they can either enable scraping with UTF-8 or they can set the NameValidationScheme to LegacyValidation fix it.
2. Update prometheus client_golang to handle duplicate label keys similarly to what OTel Go did (e.g. merge with delimiter).

I'm inclined to accept this change as-is and document how users can revert to prior behavior. I've had to work around this in our unit test for now.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.2%. Comparing base (b0d0bb9) to head (1fcabce).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6198     +/-   ##
=======================================
- Coverage   82.2%   82.2%   -0.1%     
=======================================
  Files        273     273             
  Lines      23735   23741      +6     
=======================================
+ Hits       19532   19534      +2     
- Misses      3855    3858      +3     
- Partials     348     349      +1     

see 2 files with indirect coverage changes

[MrAlias]

The bench test is failing. Are you waiting on feedback before it is resolved? Should I hold off on reviewing this?

[dashpole]

working on fixing it

[dashpole]

fixed

[MrAlias]

🚀

[chenjie199234]

@dashpole hello,i need some help about the Content-Type escaping
i'm using otel 1.35.0 and exporters/prometheus 0.57.0,and i'm testing with the browser
the Content-Type should be setted to what value?How to use the Content-Type to override the default underscores to noescape

[ywwg]

The magic is in the Accept header -- passing escaping=allow-utf-8 will ask for unescaped names. You can see some complete examples of Accept/ContentType pairs here: https://github.com/prometheus/common/blob/main/expfmt/encode_test.go#L100