ashb opened a new pull request, #65231:
URL: https://github.com/apache/airflow/pull/65231
This was discovered by running with a custom External DB manager that had
some
gnarly queries that ended up being locked behind this transaction.
`_single_connection_pool` replaces `settings.engine` with a
SingletonThreadPool engine. But `work_session` was created before that — it
still holds an internal reference to the old engine object.
_single_connection_pool has no way to rebind work_session.
So when _get_current_revision(session=work_session) runs on line 1203 —
inside
the _single_connection_pool() block — it calls session.connection() which
goes
through the old engine, not the SingletonThreadPool. The old engine's pool
was
disposed and recreated empty by engine.dispose(), so it creates a brand new
connection. That connection is completely outside _single_connection_pool's
control.
_single_connection_pool guarantees one connection on the new engine. It can't
prevent work_session from creating connections on the old one. The name is a
bit of a lie — it's really "single connection pool for new code that uses
settings.engine", not "single connection total."
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