Fix function tracing for New Relic Agent 5.0.0.124

[ormsbee]

Version 5.0.0.124 of the New Relic Agent changed the function tracing API. Using it the old way was resulting in many thousands of new metrics being added (each process invocation of a function trace was creating a new metric name), so we ended up with a bunch of "metrics" named like:

determine_group_permissions/<newrelic.api.web_transaction.WSGIWebTransaction object at 0x7f09bf016ad0> determine_group_permissions/<newrelic.api.web_transaction.WSGIWebTransaction object at 0x7f09bf098510> determine_group_permissions/<newrelic.api.web_transaction.WSGIWebTransaction object at 0x7f09bf0a8bd0> determine_group_permissions/<newrelic.api.web_transaction.WSGIWebTransaction object at 0x7f09bf108b50> determine_group_permissions/<newrelic.api.web_transaction.WSGIWebTransaction object at 0x7f09bf112250>

See: https://docs.newrelic.com/docs/release-notes/agent-release-notes/python-release-notes/python-agent-500124

Description:

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JIRA:

XXX-XXXX

Dependencies:

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Merge deadline:

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Installation instructions:

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Testing instructions:

1. Open page A
2. Do thing B
3. Expect C to happen
4. If D happened instead - check failed.

Reviewers:

• [ ] @edx/arch-review
• [ ] tag reviewer

Merge checklist:

• [ ] All reviewers approved
• [ ] CI build is green
• [ ] Version bumped
• [ ] Changelog record added
• [ ] Documentation updated (not only docstrings)
• [ ] Commits are squashed
• [ ] PR author is listed in AUTHORS

Post merge:

• [ ] Create a tag
• [ ] Check new version is pushed to PyPi after tag-triggered build is finished.
• [ ] Delete working branch (if not needed anymore)

Author concerns:

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[ormsbee]

It's not clear to me how to write a test that is actually meaningful here. Suggestions welcome. :-/

[nedbat]

Wow, super-crappy API design. Change the signature, but silently accept the old arguments and use them to bork the monitoring.

If we had to have a test, it would mock out new relic, report a version, and check the mock call was correct for that version. But I don't think it's worth it.

[ormsbee]

@robrap: How much do we care about the code coverage loss? I could mock it with a test, but it would seriously be creating a mock exactly for this call, and wouldn't actually guard against regressions in the real underlying lib...?