Associate `PostgresConnectionClosedException` with error code `08006`

[Richard Gomez]

Feature Request

Is your feature request related to a problem? Please describe

When the connection is closed unexpectedly it throws a PostgresConnectionClosedException. I would like to handle this scenario programmatically, however, it currently isn't possible to catch PostgresConnectionClosedException because it's package-private.

r2dbc-postgresql/src/main/java/io/r2dbc/postgresql/client/ReactorNettyClient.java

Lines 554 to 564 in a32a679

 static class PostgresConnectionClosedException extends R2dbcNonTransientResourceException { 
  
     public PostgresConnectionClosedException(String reason) { 
         super(reason); 
     } 
  
     public PostgresConnectionClosedException(String reason, @Nullable Throwable cause) { 
         super(reason, cause); 
     } 
  
 } 

For example, if I'm listening to notifications and want to restart the connection or channel.

Describe the solution you'd like

I would like for PostgresConnectionClosedException to be public so it can be explicitly caught.

Describe alternatives you've considered

Presently the only alternative I'm aware of is catching R2dbcNonTransientResourceException and checking for the "UNEXPECTED" error message. This isn't ideal because it's not as clear as catching the specific exception, and the message could change in the future.

[Mark Paluch]

Any R2dbcNonTransientResourceException that does not implement the PostgresqlException is an exceptional state that requires recovery. Driver exceptions that implement PostgresqlException are error notifications sent by the database. PostgresConnectionClosedException is a client-side exception and therefore it does not implement PostgresqlException.

We do not want to expose internal exception types as the specification already defines a public API for exception signals.

[Richard Gomez]

We do not want to expose internal exception types as the specification already defines a public API for exception signals.

Would including specific error codes in R2dbcNonTransientResourceException be a viable alternative? The MariaDB implementation includes relevant error codes (e.g. 0800), and including Postgres error codes would be more meaningful than matching the exception reason.

[Mark Paluch]

Thanks for the suggestion. Reporting connection failure with the error code 08006 makes sense.