[Sqlalchemy-tickets] Issue #3779: threadlocal engine sometimes doesn't properly close the connection (zzzeek/sqlalchemy)

[jbeluch <iss...@bi...>]

New issue 3779: threadlocal engine sometimes doesn't properly close the connection
https://bitbucket.org/zzzeek/sqlalchemy/issues/3779/threadlocal-engine-sometimes-doesnt

jbeluch:

In certain scenarios the __opencount attribute on TLConnection gets incremented but not properly decremented, which means the connection doesn't get closed properly unless you resort to _force_close(). 

Calling TLEngine.begin() returns the engine object itself which has __enter__ and __exit__ methods. While __enter__ will increment the open count, __exit__ doesn't call conn.close() so the count remains higher than it should.

Potential PR here: https://github.com/zzzeek/sqlalchemy/pull/301#issuecomment-242161104


Failing test:

~~~
    def test_tlbind_close_trans_conn(self):
         e = create_engine(testing.db.url, strategy='threadlocal')
         conn = e.contextual_connect()
         with e.begin():
             pass
         conn.close()
         assert conn.closed
~~~