How to tune polling by code in a TANGO class

Intended audience: advanced developers,

This HowTo explains how it is easily possible to tune attribute or command polling parameters in the code of a Tango class

Since Tango 8, it is possible to configure command or attribute polling within a Tango class code. A new set of polling related methods has been added to the base class Tango::DeviceImpl. These methods are similar to those you find in the Tango::DeviceProxy class when you write a Tango client. With them, you can

  • Check if a command or attribute is polled
  • Start/Stop polling for a command or a attribute
  • Get or update polling period for a polled attribute or command

In C++

Programming language: c++

To display some information related to polling of the attribute named TheAtt:

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string att_name("TheAtt");
cout << "Attribute " << att_name;

if (is_attribute_polled(att_name) == true)
   cout << " is polled with period " << get_attribute_poll_period(att_name) << " mS" << endl;
else
   cout << " is not polled" << endl;

To poll a command simply type:

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poll_command("TheCmd",250);

 If the command is already polled, this method will update its polling period to 250 mS. Finally, to stop polling the same command, type:

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stop_poll_command("TheCmd");

All these DeviceImpl polling related methods are documented in the DeviceImpl class documentation page

In Python

Programming language: python

To display some information related to polling of the attribute named TheAtt, in a DeviceImpl context type:

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att_name = "TheAtt"

if self.is_attribute_polled(att_name):
    print("{0} is polled with period {1} ms".format(att_name, self.get_attribute_poll_period(att_name))
else:
    print("{0} is not polled".format(att_name))

To poll a command, in a DeviceImpl context, simply type:

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self.poll_command("TheCmd", 250)

If the command is already polled, this method will update its polling period to 250 mS. Finally, to stop polling the same command, in a DeviceImpl context type:

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self.stop_poll_command("TheCmd")

All these DeviceImpl polling related methods are documented in the PyTango DeviceImpl class documentation page.

In Java

Programming language: java

The polling can be retrieved and modified from the DeviceManager class. Here is an example:

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import org.tango.server.annotation.Device;
import org.tango.server.annotation.DeviceManagement;
import org.tango.server.device.DeviceManager;
import fr.esrf.Tango.DevFailed;
@Device
public class Test {
    @DeviceManagement
    private DeviceManager deviceManager;
     ...
        final String attName = "TheAttr";
        if (deviceManager.isPolled(attName)) {
            System.out.println(attName + " is polled with period " + deviceManager.getPollingPeriod(attName) + " mS");
        } else {
            System.out.println(attName + " is not polled");
        }
        deviceManager.startPolling("TheCmd", 250);
        deviceManager.stopPolling("TheCmd")
        ...

   public void setDeviceManager(final DeviceManager deviceManager) {
        this.deviceManager = deviceManager;
    }
}