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:
Select any topic in the tree
View "Metadata" section in the right panel
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:
Next Steps
Topic Browser - View metadata interactively
Bridges - How data enters and exits the UNS
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