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Documentation Grafana Loki Send data Promtail Pipeline stages structured_metadata

structured_metadata

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.

Schema

YAML Copy

structured_metadata:
  # 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>] ... ]

Examples

Parse from log entry

For the given pipeline:

YAML Copy

- json:
    expressions:
      stream: stream
      traceID: traceID
- labels:
    stream:
- structured_metadata:
    traceID:

Given the following log line:

JSON Copy

{"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.

Parse from service discovery labels

For the configuration below, you can use labels from relabel_configs to use as structured_metadata:

YAML Copy

pipeline_stages:
  - structured_metadata:
      pod_uid:
      pod_host_ip:
relabel_configs:
  - action: replace
    source_labels:
      - __meta_kubernetes_pod_uid
    target_label: pod_uid
  - action: replace
    source_labels:
      - __meta_kubernetes_pod_host_ip
    target_label: pod_host_ip

Given the following discovered labels below with a log line sample log:

The structured_metadata stage would turn the discovered labels pod_uid and pod_host_ip into key-value pairs as structured metadata for the log line sample log and exclude them from creating high-cardinality streams.