bugfix(exporter): ensure response is closed

[codeboten]

Description

I was experiencing connection aborted when using the OTLP exporters to emit metrics. After reading the documentation for the requests library, it appears that if the body is not read, it is not necessarily returned to the connection pool.

Fix #4476

Type of change

Please delete options that are not relevant.

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

How Has This Been Tested?

Manually tested to validate that the connection aborted errors no longer happen.

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

[xrmx]

The metrics failure looks like a double close or something in case the response is a 200?

[codeboten]

Turns out the Response() constructor doesn't set a raw property on the response object which was causing the failures. I added a check for the property to exist, but in my manual testing that was not an issue.

[codeboten]

After further testing, the problem is caused by the Session object sending a keep-alive to the server and the server eventually deciding to close the connection. It would be possible to avoid this problem by closing the session's connection (via self._session.close()) but that would cause a new connection to be established every time, which seems wasteful.

Instead, I added a try/except around the post, to catch the ConnectionError and try to post another time (which causes the connection to be re-established successfully in this case). PTAL

[edgarrmondragon]

Hey 👋

Got here from #4476 affecting us at $workplace.

Would using requests support for urllib3-based¹ automatic retries be acceptable here?

For example, to declare that the first connection error² will be retried

from requests.adapters import HTTPAdapter
from urllib3.util import Retry

class OTLPMetricExporter(MetricExporter, OTLPMetricExporterMixin):
    def __init__():
        ...
        self._session = session or requests.Session()
        self._session.mount("https://", HTTPAdapter(max_retries=Retry(connect=1)))

Footnotes

1. https://requests.readthedocs.io/en/latest/user/advanced/#example-automatic-retries ↩

2. https://urllib3.readthedocs.io/en/stable/reference/urllib3.util.html#urllib3.util.Retry ↩

[xrmx]

That looks like a nice cleanup