Fix get exporter names condition

[dtaniwaki]

Description

With the current condition, _get_exporter_names always fails with no OTEL_TRACES_EXPORTER.

Python 3.8.2 (default, Apr 27 2020, 15:52:40)
[Clang 11.0.0 (clang-1100.0.33.17)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from opentelemetry.distro import Configurator
description should only be set when status_code is set to StatusCode.ERROR
>>> Configurator().configure()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/dtaniwaki/.pyenv/versions/3.8.2/lib/python3.8/site-packages/opentelemetry/instrumentation/configurator.py", line 50, in configure
    self._configure(**kwargs)
  File "/Users/dtaniwaki/github/opentelemetry-python/opentelemetry-distro/src/opentelemetry/distro/__init__.py", line 152, in _configure
    _initialize_components()
  File "/Users/dtaniwaki/github/opentelemetry-python/opentelemetry-distro/src/opentelemetry/distro/__init__.py", line 143, in _initialize_components
    exporter_names = _get_exporter_names()
  File "/Users/dtaniwaki/github/opentelemetry-python/opentelemetry-distro/src/opentelemetry/distro/__init__.py", line 55, in _get_exporter_names
    or trace_exporters.lower().strip() != "none"
AttributeError: 'NoneType' object has no attribute 'lower'

Type of change

Please delete options that are not relevant.

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

How Has This Been Tested?

• Tried to configure it with Configurator().configure() w/ and w/o OTEL_TRACES_EXPORTER.

Does This PR Require a Contrib Repo Change?

• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[lzchen]

This issue will only happen if OTEL_TRACES_EXPORTER is set to a blank string correct?

[lzchen]

Can we just do if trace_exporters and trace_exporters.lower().strip() != "none"?

[dtaniwaki]

That's right. 👍

[dtaniwaki]

This issue will only happen if OTEL_TRACES_EXPORTER is set to a blank string correct?

Here, the blank means the following 2 things.

1. OTEL_TRACES_EXPORTER is not set.
2. OTEL_TRACES_EXPORTER is an empty string.

[toumorokoshi]

can you change the description to be focused on the behavior of the user?

In this case, I would expect something like Fixed an unset OTEL_TRACES_EXPORTER resulting in an error.

This way a reader can identify whether their behavior is fixed or not.

[toumorokoshi]

minor nit on changelog description, all else looks good!

[dtaniwaki]

I updated the code, thanks!

[lzchen]

@dtaniwaki
Don't we already have this none check?

[toumorokoshi]

@dtaniwaki
Don't we already have this none check?

I think it was a logical oversight. Probably should have been the "and" operator rather than or.

If it's none, the first check is false so the OR statement continues, executing the second statement.

Here's what the logic does in a similar example:

>>> print(None is not None or None.lower())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'lower'

[toumorokoshi]

LGTM, thanks!