Connection leak in ConnectionFactoryImpl#tryConnect

[wyrzyk]

ConnectionFactoryImpl#tryConnect creates a new PGStream and establishes connection with the database, later it calls ConnectionFactoryImpl#doAuthentication. If ConnectionFactoryImpl#doAuthentication fails with an exception (for example 'too many connections for role'), then we can't use the connection, because PGConnections doesn't have queryExecutor and the socket is not closed. The socket is left to be closed by a Finalizer.

Driver Version?

42.2.14

Java Version?

1.8

OS Version?

Ubuntu

PostgreSQL Version?

Aurora 10.14

To Reproduce

I run a stress test on an app and reach a connection saturation on the database site. After the test, the number of connections remained high. I took a heap dump from the application and saw that there's not many PGConnections, but the app kept hundreds of open SocksSocketImpl. The connections were accessible only by the finalizer, but the finalizer was not processing them (the sockets were not enqueued yet.).

I tried to reproduce it with a minimal, reproducible example, but it seems it would need to push both GC and DB to reproduce the issue (socket connections going to old gen and not being closed for a longer period).

Expected behaviour

I'd expect to close the socket as soon as possible, when we know it can't be used anymore.

And what actually happens:
Finalizer closes the socket (at some point in the future).

[davecramer]

closed with PR #2351

[buitcj]

@wyrzyk SELECT pg FROM org.postgresql.jdbc.PgConnection pg WHERE (pg.queryExecutor = null) does not appear to work when I connect to the pg instance (ERROR: improper qualified name). Should this command work without any further steps? Is there any way to query the instance to tell if I'm hitting the issue that you've fixed?

[davecramer]

@wyrzyk SELECT pg FROM org.postgresql.jdbc.PgConnection pg WHERE (pg.queryExecutor = null) does not appear to work when I connect to the pg instance (ERROR: improper qualified name). Should this command work without any further steps? Is there any way to query the instance to tell if I'm hitting the issue that you've fixed?

Ok, no this command should not work.