Command polling behaviour

Development Python
1

I have a device with a number of commands. I want to start polling on a particular command (no input parameters). This is achieved with the poll_command(self, cmd_name, period) method. However, for some reason, the command is not being polled.

If instead, I start polling on the Status of the device, and then consequently start polling on my command, I can see from the stdout that both commands are being polled. So this works:

proxy.poll_command(‘Status’, 5000)
proxy.poll_command(‘my_command’, 5000)

Weirdly though, if I go in Jive to look at which commands are being polled, I can see that Status is marked as polled (ticked), whilst ‘my_command’ is not. If I try to check this programmatically from ITANGO, I am given the same information (TRUE for ‘Status’, and FALSE for ‘my_command’).

If I stop polling on Status, then the run on ‘my_command’ stops as well! Restarting polling on ‘Status’ does not cause ‘my_command’ to run again.

I have then deleted the device from the database, added it again, started the device server, and tried to poll my command from Jive. The command runs a single time, and doesn’t run again. If I try to stop polling (again from Jive), I get an error saying:

Desc → Device test/tile/1 is not polled
Reason → API_DeviceNotPolled
Origin → DServer::rem_obj_polling
Desc → Cannot execute command RemObjPolling on dserver/Tile_DS/test
Reason → TangoApi_CANNOT_EXECUTE_COMMAND
Origin → Connection.command_inout()

After this error dialog, Jive still shows the command as “unticked”. I try to tick it again (to poll), and I get a new error:

Desc → The polling threads pool is full.
Device test/tile/1 should be polled by the thread already polling but this device is not defined in the polled device map!!
Reason → API_PolledDeviceNotInPoolMap
Origin → Util::create_poll_thread
Desc → Cannot execute command AddOjbPolling on dserver/Tile_DS/test
Reason → TangoApi_CANNOT_EXECUTE_COMMAND
Origin → Connection.command_inout()
Desc → Cannot poll object my_command
Reason → TangoApi_CANNOT_POLL_OBJECT
Origin → DeviceProxy(test/tile/1).poll_object()

I’d really need some help with this. I am using PyTango 8.1.8.

2

It might have something to do with the device server.

I just tried with TangoTest (sys/tg_test/1/DevVoid) and it works fine.

Could you try this as well?

3

Hi,

Thanks for the reply. Indeed it works. And I have solved my problem.

Basically the logic of “my_command” was to stop polling on all other currently polled commands prior to starting to poll the new command. Inherently, “my_command” is registered as “polled” before the command is actually executed even once, and therefore I was starting and stopping the polling on it almost instantly. In scenarios like this, there seems to be a mismatch between which commands are actually being polled and which commands seem to be “registered” as polled. It all makes sense now - I just didn’t know this :slight_smile:

Thanks,
Andrea

4

Glad you got it to work!