Fix psycopg2 instrument_connection AttributeError

[tammy-baylis-swi]

Description

"Breaking bugfix": this includes removal of the @staticmethod decorators from this instrumentor's instrument_/uninstrument_connection methods because the following approach sets/gets instrumentor instance-level attributes. The methods were made static in #549. Not sure if it helps my argument but I'll note that the instrument_connection methods for the instrumentors of aiopg, DB-API integration, mysql-connector, and the util-http are not static (anymore?) either. Also, the existing unit tests call it as Psycopg2Instrumentor().instrument_connection(cnx) anyway and the documentation does not provide any examples.

Removes the attempt to set attribute connection._is_instrumented_by_opentelemetry because psycopg2.extensions.connection does not allow setting of extra attributes and we get AttributeError. To preserve this behavior, replaces with a set to instrumentor instance-level _is_instrumented_by_opentelemetry as defined by inherited BaseInstrumentor (introduced in this PR). We only need to set for instrument_connection and not _instrument because the latter's caller, BaseInstrumentor.instrument, does it.

Similar AttributeError also happened with setattr for connection._otel_orig_cursor_factory so instead we store the value at instrumentor attribute _otel_cursor_factory. Since the call to instrument_connection is done at the connection level I think it's ok to store at this level instead of one more granular like the custom connection proxy class.

Also fixes the documentation a bit.

Fixes #2522

Alternative fix

An alternative fix that could keep these methods static is in this other PR: #2795. However, that approach removes connection.cursor_factory parts that might be needed for the fix in #246 to support JSON and JSONB types of DB columns. It also stops using _is_instrumented_by_opentelemetry. See also PR comment.

Please let me know what you think! I'm fine with whichever approach.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• tox -e py312-test-instrumentation-psycopg2
• Instrumented db client app that calls Psycopg2Instrumentor.instrument_connection
• Instrumented db client app that calls Psycopg2Instrumentor.instrument

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

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