Connection not closed after migration when using NodaTime

[marcusber]

I've struggled for a while to understand why I see a connection open. after a migration. It took me a while to understand that it was UseNodaTime() that was behind it.

Here's a program reproducing the error.

I've tried to a bit to troubleshoot the problem and found two things in efcore.pg that may be related. When both was applied, the connection left the pool, but was still open towards the db.
Posting those as separate PRs so you could the determine the relevance.

[marcusber]

@roji Unfortunately the #3561 doesn't resolve this issue.

[roji]

You mean the program you posted above still fails?

[marcusber]

Yes, I did those changes locally and it still fails.

[marcusber]

Ok, I've come a bit further. The difference lies in when the DataReader for the migration is added.
When not using noda time, no plugins are available and the DataSource null is returned.

efcore.pg/src/EFCore.PG/Storage/Internal/NpgsqlDataSourceManager.cs

Lines 79 to 84 in fb96538

	_ when _plugins.Any() => GetSingletonDataSource(npgsqlOptionsExtension),
	// If there's no configured feature which requires us to use a data source internally, don't use one; this causes
	// NpgsqlRelationalConnection to use the connection string as before (no data source), allowing switching connection strings
	// with the same service provider etc.
	_ => null

When NodaTime is added on the other hand, a brand new DataSource is created from NpgsqlSlimDataSourceBuilder through CreateDataSource via GetSingletonDataSource.

But I have trouble getting the my head around the NpgsqlDataSourceManager. Is the idea to eventually replace the static pool in npgsql? Would it be an idea to have an operator on that class that allows clearing the datasources?

What I'm eventually after is to allow a database to be migrated. Operate on the database in exclusive mode and the be allowed to to connect to it once again. If I kill the connection, it will still be available in the PoolingDataSource and it has no idea that it has been killed and tries to reuse it. When reused it will of course throw, since it is no longer connected. I don't know if the idea here is to detect that and re-create the connection from the datasource?

I would love to read what you have to share on the subject @roji .