Open source


Warning: Structured metadata is an experimental feature and is subject to change in future releases of Grafana Loki.

The structured_metadata stage is an action stage that takes data from the extracted map and modifies the structured metadata that is sent to Loki with the log entry.

Warning: Structured metadata will be rejected by Loki unless you enable the allow_structured_metadata per tenant configuration (in the limits_config).


  # Key is REQUIRED and the name for the label of structured metadata that will be created.
  # Value is optional and will be the name from extracted data whose value
  # will be used for the value of the label. If empty, the value will be
  # inferred to be the same as the key.
  [ <string>: [<string>] ... ]


For the given pipeline:

- json:
      stream: stream
      traceID: traceID
- labels:
- structured-metadata:

Given the following log line:

{"log":"log message\n","stream":"stderr","traceID":"0242ac120002",time":"2019-04-30T02:12:41.8443515Z"}

The first stage would extract stream with a value of stderr and traceID with a value of 0242ac120002 into the extracted data set. The labels stage would turn that stream and stderr key-value pair into a stream label. The structured-metadata stage would attach the traceID and 0242ac120002 key-value pair as a structured metadata to the log line.