[BUILD] Allow shared opentelemetry_proto on non-Windows platform.

[owent]

Fixes #2096
Fixes #2139

Changes

Please provide a brief description of the changes here.

• Allow build shared opentelemetry_proto on non-Windows platform.
• Add opentelemetry_proto_grpc which contains generated grpc files (Which depends gRPC) to make OTLP Http exporter do not depends gRPC when otel-cpp is built as dynamic libraries.

Sorry for push a wrong repo by mistake before, I have moved the fix_2096 branch into my fork.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2097 (bfbe345) into main (c9f14e9) will increase coverage by 0.03%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2097      +/-   ##
==========================================
+ Coverage   87.15%   87.17%   +0.03%     
==========================================
  Files         166      166              
  Lines        4777     4777              
==========================================
+ Hits         4163     4164       +1     
+ Misses        614      613       -1     

see 1 file with indirect coverage changes

[ThomsonTan]

Is the target absl::synchronization optional, or error out if it doesn't exist?

[owent]

I'm not sure if absl::synchronization can be turn off.I'm not familar with abseil-cpp.

[lalitb]

Just curious the motive of this change - was there any build error with WITH_ABSEIL?

[lalitb]

Not sure if I am missing something, but how are we using OTELCPP_PROTO_TARGET_OPTIONS

[owent]

Sorry, it's a mistake after merging.

[lalitb]

@owent As I understand, this PR adds two new shared libs - opentelemetry_proto and opentelemetry_proto_grpc. And these shared libraries would be used by otlp_recordable, otlp_http_client and otlp_grpc_client targets. How much reduction in total otel lib size we are seeing with this change ? As this could be a breaking change if users are hardcoding the required otel libraries in their build, we should have a sufficient total size reduction to reason for a breaking change.

[owent]

@owent As I understand, this PR adds two new shared libs - opentelemetry_proto and opentelemetry_proto_grpc. And these shared libraries would be used by otlp_recordable, otlp_http_client and otlp_grpc_client targets. How much reduction in total otel lib size we are seeing with this change ? As this could be a breaking change if users are hardcoding the required otel libraries in their build, we should have a sufficient total size reduction to reason for a breaking change.

Spliting opentelemetry_proto into opentelemetry_proto and opentelemetry_proto_grpc is used to avoid to depend on gRPC when users only use OTLP HTTP exporters. The generated gRPC sources in opentelemetry_proto_grpc depend gRPC.
If users use both OTLP HTTP and gRPC exporters, I think the total size will not decreased(at lease in my tests it do not decrease), but we can allow users use only one of them to reduce the final package size.

[lalitb]

Do you think we should mentioned this PR potential breaking change here in changelog, as we have are introducing a new library?

[owent]

Do you think we should mentioned this PR potential breaking change here in changelog, as we have are introducing a new library?
Sure, the changelog is added now.

Just curious the motive of this change - was there any build error with WITH_ABSEIL?

Yes, the related CI job is here https://github.com/open-telemetry/opentelemetry-cpp/actions/runs/4707416429/jobs/8349260349 .

[lalitb]

Just curious the motive of this change - was there any build error with WITH_ABSEIL?

[lalitb]

LGTM. Thanks

[marcalff]

LGTM, thanks for the fix for 2139 as well.