Unable to add extra structured metadata as label

Grafana Loki
1

I am using Loki v3.4.2 and Grafana 11.5.1 to receive logs from an Open Telemetry Collector.

I am sending logs as structured metadata and want to add some extra fields from my log messages to show as labels in Grafana.

I have tried a number of different ways including reviewing the documentation here: Ingesting logs to Loki using OpenTelemetry Collector | Grafana Loki documentation as well as several other posts and am unable to resolve this.

My loki config has consisted of various versions of the following:

limits_config:
  allow_structured_metadata: true
  otlp_config:
    resource_attributes:
      attributes_config:
        - action: index_label
          attributes:
            - service.group
    log_attributes:
      - action: structured_metadata
        attributes:
            - Alias

I’ve tried putting the attribute under resource_attributes, in the same group as service.group, as a separate group. I’ve also tried setting the default_resource_attributes_as_index_labels value as well.

distributor:
  otlp_config:
    default_resource_attributes_as_index_labels: ["Alias", "service.group"]

The log message I’m sending to Loki looks as follows:

2025-02-19T16:22:29 ScopeLogs SchemaURL: 
2025-02-19T16:22:29 InstrumentationScope  
2025-02-19T16:22:29 LogRecord #0
2025-02-19T16:22:29 ObservedTimestamp: 2025-02-19 06:22:26.3524881 +0000 UTC
2025-02-19T16:22:29 Timestamp: 2025-02-19 06:22:26.3524881 +0000 UTC
2025-02-19T16:22:29 SeverityText: Warning
2025-02-19T16:22:29 SeverityNumber: Warn(13)
2025-02-19T16:22:29 Body: Str(Test)
2025-02-19T16:22:29 Attributes:
2025-02-19T16:22:29      -> Alias: Str(MAIN)
2025-02-19T16:22:29 Trace ID: 
2025-02-19T16:22:29 Span ID: c8dbaca31e6a3b9b
2025-02-19T16:22:29 Flags: 0

So it appears like the attribute is there. In Grafana, I can see the Alias attribute as a line in the log record, but it doesn’t appear in the label drop down. I’m not sure where to go from here, the documentation on this is very unclear.

2

Documentation is clear. It is for RESOURCE atrribute and you are not sending RESOURCE attributes - there is only log line atrribute in your example. Fix that one and it will be working.

3

In that case why does setting log_attributes not work? In previous versions I was able to promote normal attributes to labels in the otel collector, is this no longer possible? The migration steps talk about a centrally managed list of attributes.

4

I don’t know.
No.

5

Does that mean we’ve lost a feature that used to be possible? Indexing attributes as labels seems like a common use case.

6

I worked it out. The answer is to use the Otel transform processor to set a resource attribute based on a log attribute:

  transform:
    error_mode: ignore
    log_statements:
        - set(resource.attributes["Alias"], log.attributes["Alias"])
7

Common use case and common problem for administrator. Typical user will index everything (hard cardinality data included), because everything is important - it will be admin/infra/cost problem to deal with it.

So it is win from admin perspective: user doesn’t have an option to make a mess and admin has obtained an option to enforce some (good) label hygiene.

8

That’s one option from many. You can generate resources atttribute at the log source properly, so then you don’t need any fidling with attributes on the collector side.