Fix import when trace is missing from opentelemetry

[nicoloboschi]

otel dependency is optional but if I try to use latest elastic client it fails to bootstrap due to

../../../vdp/config_verification/elastic_sink/elastic_config_verification.py:21: in <module>
    from elasticsearch import Elasticsearch
../../../../.venv/lib/python3.11/site-packages/elasticsearch/__init__.py:45: in <module>
    from ._async.client import AsyncElasticsearch as AsyncElasticsearch
../../../../.venv/lib/python3.11/site-packages/elasticsearch/_async/client/__init__.py:38: in <module>
    from ._base import (
../../../../.venv/lib/python3.11/site-packages/elasticsearch/_async/client/_base.py:48: in <module>
    from ..._otel import OpenTelemetry
../../../../.venv/lib/python3.11/site-packages/elasticsearch/_otel.py:25: in <module>
    from opentelemetry import trace
E   ImportError: cannot import name 'trace' from 'opentelemetry' (unknown location)

Fix

While is usually correct to catch ModuleNotFoundError, in case of opentelemetry this is a bit different since the actual "opentelemetry" package doesn't exist at all (we got opentelemetry-api and opentelemetry-sdk) and in that case Python (3.11 in my case) throws a more generic ImportError

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[pquentin]

While is usually correct to catch ModuleNotFoundError, in case of opentelemetry this is a bit different since the actual "opentelemetry" package doesn't exist at all (we got opentelemetry-api and opentelemetry-sdk) and in that case Python (3.11 in my case) throws a more generic ImportError

Actually, the distribution packages opentelemetry-api and opentelemetry-sdk can be accessed with the import package opentelemetry. See https://packaging.python.org/en/latest/discussions/distribution-package-vs-import-package/ to understand the difference. And indeed, if I run pip install opentelemetry-api, then I can run from opentelemetry import trace without error.

Most of our CI runs without opentelemetry-api installed, from Python 3.8 to 3.13. so catching ModuleNotFoundError is generally correct. What seems to happen is that you have an opentelemetry import package that does not define trace somehow. This is possible if you run pip install opentelemetry-sdk (which will also install opentelemetry-api) and then manually run pip uninstall opentelemetry-api. At this point, the import package opentelemetry still exists (and allows access to opentelemtry.sdk) but opentelemetry.trace no longer exists. I don't think the OpenTelemetry SDK can be used without the API, but this should not break the Elasticsearch client, so the pull request looks good to me. Thank you!

[pquentin]

buildkite test this please

[pquentin]

Thank you for your contribution, it is now released as part of 8.16.0: https://github.com/elastic/elasticsearch-py/releases/tag/v8.16.0