How is one to ascertain from which Mds a metric update came?

[robsyc]

Question: Identifying the Source of a Metric Update in a Consumer Callback

After initiating a consumer and binding metric updates to a callback function, the callback receives a dictionary like:

{"Metric0": NumericMetricStateContainer DescriptorHandle="Metric0" StateVersion=6}

Where:

• The value is of type mdib.statecontainers.NumericMetricStateContainer.
• A corresponding descriptor container of type mdib.descriptorcontainers.NumericMetricDescriptorContainer can be obtained.
• The descriptor container has a parent_handle (e.g., "ch0") of type str.

Observations:

• There is a source_mds attribute on the metric, but in a basic reference mdib.xml, this is None, suggesting it's not a required property.
• The PAT mdib.xml example embeds all parent handles (mt.ch.vmd.mds) in metric handles, but can we rely on this? What if providers use incomplete metric handles?
• Ideally, determining the originating Mds.Vmd.Channel.Metric could be:
  • Accessing metric.parent_handle.parent_handle.parent_handle
  • Using an attribute like metric.source_mds
• Alternatively, it would be useful if observableproperties.bind could pass not just the metric update dict but also the epr from the source device.

Questions:

1. What is the recommended way for a callback function to determine which Mds.Vmd.Channel.Metric a metric update came from, given that only the metric handle is easily accessible?
2. Can we assume metric.ch.vmd.mds or only metric.ch.vmd or neither?
3. Is maintaining multiple consumers in a single Python app (all sending messages to the same callback) an appropriate approach, or am I looking at this the wrong way?

Thanks for your time—no rush! 🙂