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.
Replaces uses of config_get_param() in modules either with contains()
or get_string(). The config_get_param() is moved to internal headers,
as it allows seeing inside a config setting.
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.
If the routing of a session command fails due to problems with the backend
connections, a more verbose error message is logged. The added status
information in the Backend class makes tracking the original cause of the
problem a lot easier due to knowing where, when and why the connection was
closed.
Currently the bit is set so that is may be overwritten by the monitor
if the setting of the bit takes place while the monitor is performing
its monitor loop.
