PollingProbe Class
Base class for probes that require polling to detect and set model changes.
The probe wakes up every polling interval and executes the poll() method in the derived class.
PollingProbes are instantiated with either a polling interval (in milliseconds) or a cron pattern. If the polling interval is set, that's what will be used.
The cronPattern isn't available in browser-side probes.
To disable polling, set the pollInterval to 0.
More about cron formats, with examples
Constructor
PollingProbe
-
[initParams]
Parameters:
-
[initParams]Object optionalProbe initialization parameters
-
[pollInterval]Integer optionalPolling interval in milliseconds. Default: null
-
[cronPattern]String optionalCrontab syle polling pattern. Default once per second: "* * * * * *"
The format is: [second] [minute] [hour] [day of month] [month] [day of week].
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Item Index
Methods
Methods
initialize
-
attributes -
options
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.
Parameters:
-
attributesObjectInitial probe attributes sent in from the Monitor
-
optionsObjectInitialization options
-
asyncInitBooleanSet this to TRUE if the initial probe state can't be known immediately.
-
callbackFunction(error)The callback to call if asyncInit is set to true. If an error is passed, the probe will not be used.
-
onControl
-
name -
[params] -
[callback]
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.
Parameters:
-
nameStringName of the control message.
-
[params]Any optionalInput parameters specific to the control message.
-
[callback]Function(error, response) optionalCalled to send the message (or error) response.
- error (Any) An object describing an error (null if no errors)
- response (Any) Response parameters specific to the control message.
ping_control
-
params -
callback
Respond to a ping control sent from a monitor
Parameters:
-
paramsObjectInput parameters (not used)
-
callbackFunction(error, response)Called to send the message (or error) response.
- error (Any) An object describing an error
- response (String) The string 'pong' is returned as the response
release
()
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.