feat(opcua): support constant datapoints (attributes + one-time telemetry)

[palandri]

feat(opcua): support constant datapoints (attributes + one-time telemetry)

Summary

Adds first-class support for constant datapoints in the OPC-UA connector:

• Attributes with type: "constant" are sent when a device is created and on every reconnection.
• Telemetry with type: "constant" is sent once per device per gateway process (idempotent).
• Values are auto-cast (bool/int/float) when possible; otherwise kept as string.
• Telemetry is timestamped with the gateway time.
• Report strategy is respected at datapoint level via TBUtility.

Motivation

Previously, OPC-UA mapping handled datapoints backed by NodeId or path expressions but ignored constants. This feature enables:

• Populating device attributes with fixed metadata (e.g., Customer, Location).
• Emitting one-time constant telemetry (e.g., initial setup values) without requiring OPC-UA nodes.

Implementation Details

• Parsing/modeling on device side:
  • Added in-memory collections (not polled/subscribed from OPC-UA):
    • constant_attributes and constant_timeseries, collected during device config parsing in python.Device.load_values().
• Sending pipeline on connector:
  • New routine to emit constants: python.OpcUaConnector.__send_constants_for_device().
  • Invoked right after device creation in python.OpcUaConnector._create_new_devices().
  • Idempotence for constant telemetry via in-memory set created in thingsboard_gateway/connectors/opcua/opcua_connector.py.
  • Key building preserves report strategy: python.TBUtility.convert_key_to_datapoint_key().
  • Auto type inference for constant values: python.OpcUaConnector.__guess_type_and_cast().
  • Telemetry timestamp uses gateway time by default: python.TelemetryEntry.__init__().

Behavior

• Attributes (type: "constant")
  • Sent on device creation and every reconnection (devices are recreated on reconnect).
• Telemetry (type: "constant")
  • Sent exactly once per device per process (not re-sent on reconnects).

Configuration Example (new mapping format)

{
  "mapping": [
    {
      "deviceNodePattern": "Root\\.Objects\\.Device1",
      "deviceInfo": {
        "deviceNameExpressionSource": "path",
        "deviceNameExpression": "Device ${Root\\.Objects\\.Device1\\.serialNumber}",
        "deviceProfileExpressionSource": "constant",
        "deviceProfileExpression": "default"
      },
      "attributes": [
        { "key": "Customer", "type": "constant", "value": "ACME Corp" }
      ],
      "timeseries": [
        { "key": "InitialBatchSize", "type": "constant", "value": "12" }
      ]
    }
  ]
}

Casting Rules

• "true"/"false" (case-insensitive) → boolean
• -123 → integer
• 45.67 → float
• Anything else → string

Backward Compatibility

• No breaking changes. Existing path/identifier-based datapoints remain unchanged.
• The backward-compatibility adapter continues to set type: "constant" where applicable; the new pipeline now handles those entries.

Tests / Verification

• Unit tests (added in this PR):
  • tests/unit/connectors/opcua/test_constants.py
    • Validates parsing buckets for constants and idempotent behavior of one-time constant telemetry.
  • Fixture config:
    • tests/unit/connectors/opcua/data/constants/opcua_config_constants.json
• Blackbox (optional, requires TB test environment):
  • Example configuration to validate runtime behavior:
    • tests/blackbox/data/opcua/configs/uplink_configs/constants_config.json
  • Integrates with existing OPC-UA blackbox harness. Not executed as part of this PR by default.

Documentation Impact

• Update OPC-UA connector mapping docs to include:
  • Support for type: "constant" in attributes and timeseries.
  • Semantics (attributes on create/reconnect, telemetry one-time).
  • Casting rules and gateway timestamp.
  • Example mapping similar to the snippet above.

Touched Code

• Device parsing and storage:
  • thingsboard_gateway/connectors/opcua/device.py
  • python.Device.load_values()
• Connector logic:
  • python.OpcUaConnector.__send_constants_for_device()
  • python.OpcUaConnector._create_new_devices()
  • python.OpcUaConnector.__guess_type_and_cast()
• Utilities and entities (used as-is):
  • python.TBUtility.convert_key_to_datapoint_key()
  • python.TelemetryEntry.__init__()
• Tests:
  • tests/unit/connectors/opcua/test_constants.py
  • tests/unit/connectors/opcua/data/constants/opcua_config_constants.json
  • tests/blackbox/data/opcua/configs/uplink_configs/constants_config.json

Checklist

• [x] Parse/store constant datapoints (no OPC-UA read required)
• [x] Send constant attributes on create/reconnect
• [x] Send constant telemetry once per device per process
• [x] Type inference and gateway timestamp
• [x] Datapoint-level report strategy
• [x] Unit tests
• [ ] Blackbox validation on TB test environment
• [ ] Documentation and CHANGELOG updates

[samson0v]

Hi @palandri, thanks for your contribution! We really appreciate it. I will take a look at your PR soon.

[palandri]

Hello @samson0v. Do not worry, there is no hurry. I'm looking forward your opinion on this.

Cheers.

[samson0v]

Hi @palandri, I am reviewing your PR and have a question about this:

Attributes (type: "constant")
    Sent on device creation and every reconnection (devices are recreated on reconnect).
Telemetry (type: "constant")
    Sent exactly once per device per process (not re-sent on reconnects).

Why did you decide to use different strategies for sending?