The settings are different from the other fields in that they should not change
on their own. Most manipulation functions only require the settings.
Also takes into use a class for host and port data.
The monitor queries for logged in users with super-privileges and kicks them out to
prevent writes to master. Normal users can stay since their writes are prevented by
read_only. Also, the master-status is removed from the master manually to signal to
routers that no more writes should go to master.
If gtid of master is unknown (as is typical when master is down when MaxScale
starts) the domain id is guessed from the slaves instead. This is usually
safe.
If the monitor setting "replication_master_ssl" is set to on, any CHANGE MASTER TO-command
will have MASTER_SSL=1. If set to off or unset, MASTER_SSL is left unchanged to match existing
behaviour.
All servers are now updated in their own threads simultaneously. This
should reduce the possibility of having significantly different gtid:s
shown for different servers.
This fixes some situations where MaxAdmin/MaxCtrl would block and wait
until a monitor operation or tick is complete. This also fixes a deadlock
caused by calling monitor diagnostics inside a monitor script.
Concurrency is enabled by adding one mutex per server object to protect
array-like fields from concurrent reading/writing.
The monitor now continuously updates a list of enabled server events. When
promoting a new master in failover/switchover, only events that were enabled
on the previous master are enabled on the new. This avoids enabling events
that may have been disabled on the master yet stayed in the SLAVESIDE_DISABLED-
state on the slave.
In the case of reset-replication command, events on the new master are only
enabled if the monitor had a master when the command was launched. Otherwise
all events remain disabled.
The QueryResult-object remembers if a conversion failed. This makes checking
for errors more convenient, as just one check per row is required. The conversion
functions always return a valid value.
