The protocol now allows protocol modules to return JSON formatted
information about the protocol module internals. Currently this is only
implemented by the mariadbbackend module and it returns the current
connection ID on the backend server.
Removed unused and properly documented all entry points in the protocol
module API. As the removal of the `session` entry point is an backwards
incompatible change, the protocol API version was updated.
The re-authentication done in MaxScale caused multiple error packets to be
sent for the same COM_CHANGE_USER. In addition to this, the failure of
authentication did not terminate the client connection.
The change in behavior requires the test case to be changed as well.
Session commands that span multiple packets are now allowed and will
work. However, if one is executed the session command history is disabled
as no interface for appending to session commands exists.
The backend protocol modules now also correctly track the current
command. This was a pre-requisite for large session commands as they
needed to be gathered into a single buffer and to do this the current
command had to be accurate.
Updated tests to expect success instead of failure for large prepared
statements.
By making it conditional, we prevent the problems that arise when the
replication protocol is used in combination with the session state change
tracking. In addition to this, it prevents unnecessary work for routers
and filters that don't need it.
By always starting the session shutdown process by stopping the client
DCB, the manipulation of the session state can be removed from the backend
protocol modules and replaced with a fake hangup event.
Delivering this event via the core allows the actual dcb_close call on the
client DCB to be done only when the client DCB is being handled by a
worker.
Directly closing the client DCB in the backend protocol modules is not
correct anymore as the state of the session doesn't change when the client
DCB is closed. By propagating the shutdown of the session with a fake
hangup to the client DCB, the closing of the DCB is done only once.
Added debug assertions that make sure all DCBs are closed only
once. Removed redundant code in the backend protocol error handling code.
