Jaeger gRPC exporter lacking span parent structure

[plajjan]

Describe your environment
I'm running opentelemetry in a docker container on my local computer.

root@ea1e70b65e3c:/log# python3 --version
Python 3.7.3
root@ea1e70b65e3c:/log# 
(pyvenv) root@ea1e70b65e3c:/var/opt/ncs/packages/opentelemetry-exporter# python3
Python 3.7.3 (default, Jan 22 2021, 20:04:44) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import opentelemetry.version
>>> opentelemetry.version.__version__
'1.1.0'
>>> 

Steps to reproduce
I have an application that is using the OpenTelemetry library and is exporting data just fine to Jaeger via the Thrift interface. I would need to export data over IPv6 though and the Thrift over UDP is hard coded to IPv4 (see #1559), thus I'm trying to use gRPC. I have succeeded in getting data exported but the data is lacking the parent/child structure.

Reading https://github.com/open-telemetry/opentelemetry-python/blob/main/exporter/opentelemetry-exporter-jaeger-proto-grpc/src/opentelemetry/exporter/jaeger/proto/grpc/translate/__init__.py, I don't see that it is really reading out the parent structure and exporting. Am I missing something or is it just missing?

In the Thrift model, there is a parentSpanId. In gRPC it seems to be modeled differently, like there's a list of references that can be of the type CHILD_OF or FOLLOWS_FROM. It is set here https://github.com/open-telemetry/opentelemetry-python/blob/main/exporter/opentelemetry-exporter-jaeger-proto-grpc/src/opentelemetry/exporter/jaeger/proto/grpc/translate/__init__.py#L254 and extracted using https://github.com/open-telemetry/opentelemetry-python/blob/main/exporter/opentelemetry-exporter-jaeger-proto-grpc/src/opentelemetry/exporter/jaeger/proto/grpc/translate/__init__.py#L318 but it only looks at the span links, not at the normal span parent relation.

What is the expected behavior?
Seeing child spans of parents etc. A nested structure.

What is the actual behavior?
A flat list of spans.

Additional context