Queries from multiple spawns crash about crystal-mysql HOT 2 CLOSED

I've been able to debug this further.

MySql::ResultSet#do_close

def do_close
    super

    while move_next
    end

    if row_packet = @row_packet
      row_packet.discard
    end
end

With the above code when the @row_packet is still filled, the exception is thrown, because the call to super closes the connection via statement.release_connection

This causes the connection to be closed when the max_idl_pool_size is reached. The default is 1 so in the above script the connection will be closed.

When this occurs the connection is closed before the row_packet is discarded, which means the remaining bytes cannot be skipped in the closed socket, hence the Closed stream (IO::Error)

I was able to get rid of the exception by calling super in an ensure block, this causes the connection to be closed after discarding the remaining row_packet.

def do_close
    while move_next
    end

    if row_packet = @row_packet
      row_packet.discard
    end
ensure
    super
end

from crystal-mysql.

Nice catch! I agree that the super should be called after the rows are discarded.
I think it would be great to add this case to the shared specs in crystal-db, maybe adding a slow_scalar_query that will perform the sleep to.

from crystal-mysql.