Metadata and Tracing

Every message in the UNS carries metadata that preserves its origin and transformation history. This enables troubleshooting and data lineage tracking.

Understanding Metadata

When data flows through the UNS, metadata accumulates at each step:

{
  "_incomingKeys": "s7_address",
  "_initialMetadata": "{\"s7_address\":\"DB1.DW20\"}",
  "bridged_by": "protocol-converter_pump-bridge",
  "data_contract": "_pump_v1",
  "data_contract_name": "_pump",
  "data_contract_version": "1",
  "kafka_msg_key": "umh.v1.enterprise.chicago.packaging.line-1.pump-01._pump_v1.inlet_temperature",
  "kafka_timestamp_ms": "1758290100065",
  "kafka_topic": "umh.messages",
  "location_path": "enterprise.chicago.packaging.line-1.pump-01",
  "s7_address": "DB1.DW20",
  "name": "inlet_temperature",
  "topic": "umh.v1.enterprise.chicago.packaging.line-1.pump-01._pump_v1.inlet_temperature",
  "umh_topic": "umh.v1.enterprise.chicago.packaging.line-1.pump-01._pump_v1.inlet_temperature"
}

Tracing Data Flow

Bridge Metadata

Every bridge adds metadata to identify the source:

# In Topic Browser or when consuming:
bridged_by: "protocol-converter_pump-bridge"    # Which bridge created this
location_path: "enterprise.chicago.packaging"    # Where it came from
data_contract: "_pump_v1"                       # What model was applied

Note: The exact format of bridge metadata may vary by implementation.

Accessing Metadata

In Topic Browser

The Management Console shows metadata in the details panel:

1. Select any topic in the tree

2. View "Metadata" section in the right panel

3. See all headers including original tags

For details, see Topic Browser documentation.

Further metadata: Each input or processing step adds its own metadata. For complete field documentation, see:

• Benthos-UMH Input Plugins

Next Steps

• Topic Browser - View metadata interactively

• Bridges - How data enters and exits the UNS