The logging in the RWSplit::select_connect_backend_servers was quite
cumbersome and doing the logging when the connection is created makes for
a more information rich output (we know what servers were taken into use
and when).
Changed the log messages to use the names of the servers instead of the
address and port.
It is possible that the routing fails even if master_reconnection is
enabled and a second master is available. This is the case when a
transaction is open or autocommit is disabled which is what the
mxs359_master_switch test tests.
The tasks themselves now control whether they are executed again. To
compare it to the old system, oneshot tasks now return `false` and
repeating tasks return `true`.
Letting the housekeeper remove the tasks makes the code simpler and
removes the possibility of the task being removed while it is being
executed. It does introduce a deadlock possibility if a housekeeper
function is called inside a housekeeper task.
The class now does all of the work and the API wraps the calls to the
member methods. Using an STL container makes the list management a lot
more convenient.
The old hkheartbeat variable was changed to the mxs_clock() function that
simply wraps an atomic load of the variable. This allows it to be
correctly read by MaxScale as well as opening up the possibility of
converting the value load to a relaxed memory order read.
Renamed the header and associated macros. Removed inclusion of the
heartbeat header from the housekeeper header and added it to the files
that were missing it.
This is a proof-of-concept that validates the query retrying method. The
actual implementation of the query retrying mechanism needs more thought
as using the housekeeper is not very efficient.
The code for figuring out the where to send a statement does no
longer depend upon RWSplitSession but only on QueryClassifier.
So now the functionality can be moved into QueryClassifier after
which further cleanup and streamlining can be done.
A readwritesplit session must have a client DCB and the DCB must
have data, otherwise the system is seriously broken. So no point
in checking for that and logging an error. Situations like that
might have been possible in the olden days when a session could
be manipulated by multiple threads at the same time.
A member variable and local variable had the same names which caused the
member variable to not be used. With the change in the member variable,
this went unnoticed.
The use of `router_options=master,slave` was not working as expected. This
was mostly caused by the master bit checks using a bitwise AND instead of
comparing equality. In addition to this, the master would not be
considered a valid candidate if both slaves and masters were available.
The MASTER_GTID_WAIT "prefix" should only be added if it fits into one
packet. This is not a complete solution as it prevents queries larger than
16MB from benefiting from the consistent reads.
Keeping track of the closed state of the session inside the router session
itself is not needed as the MaxScale core should already do that.
The skygw_chk_t variables are rather meaningless and are obsoleted by
Valgrind/ASAN.
Most of the funtionality is now a member function of either the RWSplit or
RWSplitSession class. This removes the need to pass the router and session
parameters to all functions.
