User event - TANGO Controls

# 6 months ago
AlexS	Hello Tango Community, I have been using Tango for a while, but have never used "User event". Are there any examples or use-cases? Regards.

# 6 months ago
Andy	Hi Alex, User events are device server dependent and can be used to send an event which is device server specific and does not fit into the strict definition of CHANGE, PERIODIC or ARCHIVE or any of the other pre-defined event types. Because they are device dependent they must be triggered by the device server using the manual push call. Examples are anything you need to inform clients about via events e.g. DeviceOnFire Here is some documentation on pushing events from the server: https://tango-controls.readthedocs.io/en/latest/development/device-api/generating-events.html#generating-events-in-a-device-server Andy Edited 6 months ago

# 6 months ago

Andy

Hi Alex,

User events are device server dependent and can be used to send an event which is device server specific and does not fit into the strict definition of CHANGE, PERIODIC or ARCHIVE or any of the other pre-defined event types. Because they are device dependent they must be triggered by the device server using the manual push call. Examples are anything you need to inform clients about via events e.g. DeviceOnFire

Here is some documentation on pushing events from the server:

https://tango-controls.readthedocs.io/en/latest/development/device-api/generating-events.html#generating-events-in-a-device-server

Andy

Edited 6 months ago

# 6 months ago
AlexS	Hi Andy, Thanks for your reply! I understand the general concept of a user event. I'm curious about the experience of using it in "real world" devices. At the moment I can think of the following use-cases: sending attribute value with some meta-data, sending a kind of "diff" for a large attribute.

# 6 months ago
Andy	I don't have a real world example in mind right now, I will ask around to see how it is used at the ESRF and feedback to the forum …

# 6 months ago
AlexS	I've performed some tests and checked source code. It seems that current ZMQ-based implementation does not use filterable_names and filterable_vals arguments. More over, I misunderstood the purpose of these arguments. So my idea of attaching meta information was wrong.

# 6 months ago
Anton	Hi Alex Yes, you are right. The ZMQ events don't use those parameters. They were only used by the previous event system: notifyd. We also discovered that recently in PyTango, and have updated the docstrings. That will be in PyTango v10.0.0. /Anton

# 3 months ago
Thomas	Hi AlexS AlexS I'm curious about the experience of using it in "real world" devices. One use case could be to inform subscribers when a device is leaving init_device or is entering delete_device. This allows subscribers to know when a device should be ready or that it will be unavailable. A simple example for PyTango is here. Cheers, Thomas