Initialize the probe

This is called on the probe during construction. It contains the probe initialization attributes and an option to make probe construction asynchronous.

Probe implementations can defer the initial response to the monitor until the initial state is loaded. This allows the callback on Monitor.connect() to have the complete initial state of the probe when called.

If the initial probe state cannot be determined in initialize, it should set the options.asyncInit option to true, and call the options.callback(error) once the initial state is determined.

// Asynchronous initialization
options.asyncInit = true;
var callback = options.callback

If asyncInit is set to true, the callback must be called once the initial state of the probe is known (or in an error condition).

// Set the initial state, and call the callback
this.set(...);
callback(null);

See the initialize method of the FileProbe probe for an example. It defers returning the probe to the monitor until the initial file contents are loaded.

Dispatch a control message to the appropriate control function.

This is called when the control() method of a monitor is called. The name determines the method name called on the probe.

The probe must implement a method with the name {name}_control(), and that method must accept two parameters - an input params and a callback. The callback must be called, passing an optional error and response object.

For example, if the probe supports a control with the name go, then all it needs to do is implement the go_control() method with the proper signature. See ping_control() for an example.

Respond to a ping control sent from a monitor

Release any resources consumed by this probe.

This can be implemented by derived classes that need to be informed when they are to be shut down.

Probes that listen to events should use this method to remove their event listeners.