fix: otlp json encoding

[seemk]

Which problem is this PR solving?

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #4216

Short description of the changes

Fixes the breakage introduced in #4062 where OTLP JSON encoding was encoding the intermediate low and high bytes directly to JSON, but in JSON mapping fixed64 can only be either a string or a number.

Removed usage of the parts taken from long.js and used BigInt instead with a fallback to the old worse precision hrTimeToNanoseconds from core if BigInt is not available.

Refactored the createExport{Trace,Metrics,Logs}ServiceRequest calls to unified options and an encoder (getOtlpEncoder), added tests for the encoder.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tested manually against collector with gRPC, http/proto, http/json exporters.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added

[codecov]

Codecov Report

Merging #4220 (c0145d8) into main (586def4) will decrease coverage by 1.71%.
The diff coverage is 66.66%.

❗ Current head c0145d8 differs from pull request most recent head fe78777. Consider uploading reports for the commit fe78777 to get more accurate results

@@            Coverage Diff             @@
##             main    #4220      +/-   ##
==========================================
- Coverage   92.24%   90.54%   -1.71%     
==========================================
  Files         331      159     -172     
  Lines        9481     3765    -5716     
  Branches     1999      837    -1162     
==========================================
- Hits         8746     3409    -5337     
+ Misses        735      356     -379     

Files	Coverage Δ
...tlp-http/src/platform/browser/OTLPTraceExporter.ts	100.00% <100.00%> (ø)
...lp-http/src/platform/browser/OTLPMetricExporter.ts	100.00% <100.00%> (ø)
...-otlp-http/src/platform/browser/OTLPLogExporter.ts	83.33% <0.00%> (ø)

... and 175 files with indirect coverage changes

[evantorrie]

but in JSON mapping fixed64 can only be either a string or a number.

That linked table seems to indicate that fixed64 is preferred to be a string, whereas fixed32 is preferred to be a number (although either would be accepted). I see that this PR does output the fixed64 as a string, so seems good to me.

[trentm]

It would be helpful if this branch could be updated to the latest in "main". That should hopefully fix the "Unit Tests / ..." check failures, now that #4238 has gone in.

[evantorrie]

Is there any way to expedite getting this patch in?

For some users, the last release (1.17.1 and the experimental packages 0.44.0) is broken. Web-based JSON exporters in this release broke by sending data that does not conform to the JSON serialization of the protobufs expected by the OpenTelemetry Collector.

That release was on October 10, so we are getting close to a month now where we have a broken release as the "latest release".

Could we please get this fix merged and a new release (1.17.2? 0.44.1?) pushed ASAP?

[pichlermarc]

Looks like the test faliures that were fixed by #4238 held this PR up quite a bit while I was out of office 😞

I ran some local tests with the exporter example and the changes look good to me. Thank you @seemk for taking care of this.

I'll push a commit to this PR to move the changelog entry - then I'll merge; I'll continue to review PRs in this repo for the rest of my day and then I'll open a release PR so we can get this published as soon as possible.