Add optional Application Name to Postgres Connection Info

[neilt]

Is your feature request related to a problem? Please describe.
Our problem is how to determine which of our applications is causing problems by observing the Postgres database connections in the Postgres Server.

Describe the solution you'd like
We have multiple applications connecting to the Postgres database and would like to be able to differentiate connections between our various applications. Traditionally, we have used the application name. We would like to be able to optionally specify the application name in PostgresConfiguration.

Describe alternatives you've considered
Any solution would work as long as we can determine which application is connected to which pids in the Postgres server.

We thought about just using SET application_name = 'test_activity'; after the connection is established, but could not figure out how to get this set in all connections from the pool in all threads.

Additional context
None.

[fabianfett]

I think this is an issue for PostgresKit. @gwynne?

[neilt]

Yes it does apply to PostgresKit. Sorry about that, I should have caught it. Our intent at this point was to be using postgres-nio, but we are experimenting with postgres-kit and it seems we've co-mingled the code.

But I looked at PSQLConnection.Configuration and there is no way to set application_name here during the connection either.

Should I move or add this issue to PostgresKit. It seems they are related.

[fabianfett]

Yes. The problem you are describing can be resolved with a custom Source when using the AsyncKit EventLoopGroupConnectionPool.

https://github.com/vapor/async-kit/blob/main/Sources/AsyncKit/ConnectionPool/EventLoopGroupConnectionPool.swift

I guess just reask your question in PostgresKit again and @gwynne can probably help you out there.