Remove _total from duplicate untyped Sums before export

[damemi]

Fixes #677

updates GMP exporter's custom GetMetricName() to remove _total from Sums which have the double-export untyped-metric attribute, if total was not present in the original metric name (before being normalized by OTel's prometheus.BuildPromCompliantName() function).

We need this because the extra untyped Sum metric is added at the ExtraMetrics extension point, which is before name normalization happens for the individual metric types.

Alternatively, the extra metric could be added after name normalization (ie, copy the normalized Gauge metric name to a new Sum after this line in gaugePointToTimeSeries). But that would require refactoring to add a new extension point, which is not worth the effort with a long term upstream plan in the works. The current method takes advantage of existing metric handling for Gauges+Sums as well, such as cumulative normalization.

[dashpole]

unit test would be useful here

[damemi]

unit test would be useful here

added a unit test

[codecov]

Codecov Report

Merging #678 (9dd6a16) into main (191af02) will decrease coverage by 0.23%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##             main     #678      +/-   ##
==========================================
- Coverage   69.01%   68.79%   -0.23%     
==========================================
  Files          36       36              
  Lines        4651     4679      +28     
==========================================
+ Hits         3210     3219       +9     
- Misses       1288     1308      +20     
+ Partials      153      152       -1     

Impacted Files	Coverage Δ
...tor/integrationtest/testcases/testcases_metrics.go	85.52% <0.00%> (-14.48%)	⬇️
...porter/collector/googlemanagedprometheus/naming.go	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[dashpole]

One thing we will have to think about going forward is that we won't have access to the "unknown" flag from a counter. The "unknown" flag will be gauge-specific. That will make our current approach of looking at labels in the naming function no longer work. We don't need to solve that here, but worth noting

[damemi]

fyi @ridwanmsharif: if you see double-exported metrics with _total added to the counter, this will fix that

[dashpole]

@damemi it looks like this removes _total from all counters, not just those that came from untyped. We should only remove _total from counters that come from unknown metrics.

[damemi]

@damemi it looks like this removes _total from all counters, not just those that came from untyped. We should only remove _total from counters that come from unknown metrics.

ugh yup, missed that... #680