feat: stackdriver trace exporter

[dyladan]

Which problem is this PR solving?

• port stackdriver trace exporter from OpenCensus. #530

Short description of the changes

• Implement a stackdriver trace exporter

[dyladan]

I created this PR as a draft because I still have some open questions:

1. The opencensus version included a g.co/agent attribute on every trace that had the version of the tracing agent. I ported that, but i'm not sure if we want or need it.
   1. Is this some sort of special key name or just something OC did?
   2. Are there others that should be included?
   3. Should the exporter be adding any attributes at all to the spans, or should this work be done by the SDK?
2. tests not done
3. right now number attributes are rounded because GCP only accepts ints. is this acceptable?
4. attributes that are not number | boolean | string are dropped because stackdriver can't accept other value types

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@bcded46). Click here to learn what that means.
The diff coverage is 94.55%.

@@            Coverage Diff            @@
##             master     #648   +/-   ##
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  Coverage          ?   89.97%           
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  Files             ?      219           
  Lines             ?    10346           
  Branches          ?      945           
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  Hits              ?     9309           
  Misses            ?     1037           
  Partials          ?        0

Impacted Files	Coverage Δ
...ackages/opentelemetry-web/src/WebTracerRegistry.ts	100% <ø> (ø)
...entelemetry-exporter-zipkin/test/transform.test.ts	100% <ø> (ø)
packages/opentelemetry-web/test/WebTracer.test.ts	0% <0%> (ø)
...metry-core/src/trace/instrumentation/BasePlugin.ts	86.84% <100%> (ø)
...ry-plugin-dns/test/functionals/dns-disable.test.ts	100% <100%> (ø)
...opentelemetry-core/src/trace/NoopTracerRegistry.ts	100% <100%> (ø)
...telemetry-plugin-document-load/src/documentLoad.ts	97.95% <100%> (ø)
...lugin-https/test/functionals/https-disable.test.ts	100% <100%> (ø)
packages/opentelemetry-tracing/src/utility.ts	100% <100%> (ø)
...ry-tracing/test/export/ConsoleSpanExporter.test.ts	100% <100%> (ø)
... and 48 more

[mayurkale22]

This is a great start, added few initial comments.

[dyladan]

@mayurkale22 is this really xxl with just 20 files changed? How are you differentiating between xl and xxl?

[mayurkale22]

https://github.com/open-telemetry/opentelemetry-js/labels?utf8=%E2%9C%93&q=size => feel free to suggest or edit the labels or descriptions.

[mayurkale22]

@draffensperger it would be great, if you can review and approve this one!

[obecny]

types and transform functions they are almost the same as for ExporterCollector. Seems like this is the same functionality with regards to types and data manipulation. Maybe it should be reused or extended, otherwise I see many duplications here.

[dyladan]

types and transform functions they are almost the same as for ExporterCollector. Seems like this is the same functionality with regards to types and data manipulation. Maybe it should be reused or extended, otherwise I see many duplications here.

This is because the types for the collector exporter came from opencensus which in turn got its types from stackdriver because they are both google projects. We have to keep them separate because while they are very similar, they are different projects.

[obecny]

Are you able to add some screenshots to be able to see how the stackdriver spans looks like ?

[dyladan]

I don't have time to do it today. if @mayurkale22 merges this while i'm on vacation I can add it in a separate PR

[draffensperger]

Looks good! Thanks for making it infer the project ID from the credentials when not specified. Had just a few minor suggestions about making it a bit clearer in the dos that service accounts aren't needed when running on GCP. Other than that, looks good!

[mayurkale22]

@dyladan Could you please resolve the last round of comments, I think it is good to go after that.

[dyladan]

@dyladan Could you please resolve the last round of comments, I think it is good to go after that.

yes i'll do that today. i've been spending a lot of time on the named tracers spec recently and this got lost in the shuffle

[dyladan]

@mayurkale22 seems like this is probably good to go now whenever you're ready

[obecny]

I don't have time to do it today. if @mayurkale22 merges this while i'm on vacation I can add it in a separate PR

ping on that

[dyladan]

@obecny done