Add sampler type tag to collector ingestion metrics

[guanw]

Which problem is this PR solving?

• No metrics tag for sampler.type #1574

Short description of the changes

• This pull request adds new tag representing sampler types to metrics

[codecov]

Codecov Report

Merging #1576 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #1576      +/-   ##
=========================================
+ Coverage    98.8%   98.8%   +<.01%     
=========================================
  Files         191     191              
  Lines        9102    9116      +14     
=========================================
+ Hits         8993    9007      +14     
  Misses         85      85              
  Partials       24      24

Impacted Files	Coverage Δ
cmd/collector/app/metrics.go	100% <100%> (ø)	⬆️
model/span.go	100% <100%> (ø)	⬆️

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[jpkrohling]

If we have one service, "hotrod", deployed in two hosts/pods, each with a different sampler (const, ratelimiting), we'd then end up with two metrics, right?

What's the impact of this PR on people who are using the previous version of this metric?

[black-adder]

What's the impact of this PR on people who are using the previous version of this metric?

Depending on how users have setup their dashboards, users may see the service.traces.received and service.spans.received metrics now split by the sampler_type label. But if users have metrics setup like: sum(service.traces.received) by (svc, debug, format) then they should see no difference as the two new metrics will be summed.

[yurishkuro]

Do we need to be changing service.spans.received? Sampler is only defined on the root span and that's what traces.received metric is already capturing.

[guanw]

Do we need to be changing service.spans.received? Sampler is only defined on the root span and that's what traces.received metric is already capturing.

Yeah you're right. The samplerType metric will only be applied to trace.received. For spans.received it will simply pass.

[guanw]

@yurishkuro is there anyway to debug travis ci test failure? make test-ci runs fine on my local setup and I couldn't reproduce the error by manually running L11-16 of build-all-in-one-image.sh locally either. (As quoted by Won: Best kind of bug)

[yurishkuro]

don't know if you can debug it, but the log output suggests a timeout - #1583

[codecov]

Codecov Report

Merging #1576 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1576      +/-   ##
==========================================
+ Coverage    98.8%   98.81%   +<.01%     
==========================================
  Files         191      191              
  Lines        9095     9162      +67     
==========================================
+ Hits         8986     9053      +67     
  Misses         85       85              
  Partials       24       24

Impacted Files	Coverage Δ
cmd/collector/app/metrics.go	100% <100%> (ø)	⬆️
model/span.go	100% <100%> (ø)	⬆️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 09dad38...6eeae79. Read the comment docs.