Previously, runtime monitor modifications could directly alter monitor fields,
which could leave the text-form parameters and reality out-of-sync. Also,
the configure-function was not called for the entire monitor-object, only the
module-implementation.
Now, all modifications go through the overridden configure-function, which calls the
base-class function. As most configuration changes are given in text-form, this
removes the need for specific setters. The only exceptions are the server add/remove
operations, which must modify the text-form serverlist.
Worker::STOPPED -> MONITOR_STATE_STOPPED
Worker::POLLING -> MONITOR_STATE_RUNNING
Worker::PROCESSING -> MONITOR_STATE_RUNNING
By defining the monitor state from the worker state there is
no risk they will ever get out of sync. And there is one thing
less to maintain.
As m_servers is a member of Monitor, it is better if the closing
of the MYSQL connections is done there, so that derived classes
do not need to remember doing that.
When the servers of a service are defined by a monitor, then
at startup all servers of the monitor should be added to relevant
services. Likewise, when a server is added to or removed from a
monitor at runtime, those changes should affect services as well.
However, whether that should happen or not depends upon the monitor.
In the case of the Clustrix monitor this should not happen as it
adds and removes servers depending on the runtime state of the
Clustrix cluster.
If the servers of a service are defined by a monitor (the config
has 'cluster=SomeMonitor'), then the addition of a server to a
a monitor should lead to that server being added to the service.
The services whose servers are defined using a monitor, will
now be populated from the monitor.
Note, no consideration has yet been given to runtime changes.
The manipulation functions are currently static so that the container can be initialized
if required. This will be fixed later.
The new functions are taken into use in monitor management.
Since the settings are now protected fields, all related functions were
moved inside the monitor class. mon_ping_or_connect_to_db() is now a method
of MXS_MONITORED_SERVER. The connection settings class is defined inside the
server since that is the class actually using the settings.
The class MonitorManager contains monitor-related functions that should not
be called from modules. MonitorManager can access private fields and methods
of the monitor.
The functions stores the current server status to the monitored
server's mon_prev_status and pending_status fields.
To be used at the start of the monitor loop, before the pending
status fields are updated.
Most of the ones still remaining outside are special cases.
Also, removed locking from status manipulation functions as it
has not been required for quite some time.
