Context

Currently the Go driver never attempts to detect connections that were closed by the other side when checking out connections. As a result, it's possible to return a connection that's been closed by the other side where any read or write operations will immediately fail. Instead, we should check if the connection has been closed when checking out a connection.

Definition of done

• Check if a connection has been closed when checking out the connection. If it has, discard it and try to return another connection.

Pitfalls

Checking if a connection has been closed by the other side isn't as straightforward as calling an IsClosed method on the connection. These are some possible approaches:

• Make a non-blocking read request for the connection. If an error is returned, the connection is closed.
  • That depends on the ability to call a non-blocking read, which may or may not be practical in Go.
• Call conn.Read with a very short read deadline. If an error is returned, the connection is closed.
  • We need to make sure conn.Read returns before using the connection to run an operation. Otherwise, there will be concurrent read and write requests, which will lead to undefined behavior.
• Investigate the APIs available by type-asserting the conn to a *TCPConn, possibly using the underlying file descriptor to figure out its state.
  • It's not clear if that's possible.