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:

1string att_name("TheAtt");
2cout << "Attribute " << att_name;
3
4if (is_attribute_polled(att_name) == true)
5   cout << " is polled with period " << get_attribute_poll_period(att_name) << " mS" << endl;
6else
7   cout << " is not polled" << endl;

To poll a command simply type:

1poll_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:

1stop_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:

1att_name = "TheAtt"
2
3if self.is_attribute_polled(att_name):
4    print("{0} is polled with period {1} ms".format(att_name, self.get_attribute_poll_period(att_name))
5else:
6    print("{0} is not polled".format(att_name))

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

1self.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:

1self.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:

 1import org.tango.server.annotation.Device;
 2import org.tango.server.annotation.DeviceManagement;
 3import org.tango.server.device.DeviceManager;
 4import fr.esrf.Tango.DevFailed;
 5@Device
 6public class Test {
 7    @DeviceManagement
 8    private DeviceManager deviceManager;
 9     ...
10        final String attName = "TheAttr";
11        if (deviceManager.isPolled(attName)) {
12            System.out.println(attName + " is polled with period " + deviceManager.getPollingPeriod(attName) + " mS");
13        } else {
14            System.out.println(attName + " is not polled");
15        }
16        deviceManager.startPolling("TheCmd", 250);
17        deviceManager.stopPolling("TheCmd")
18        ...
19
20   public void setDeviceManager(final DeviceManager deviceManager) {
21        this.deviceManager = deviceManager;
22    }
23}