opentelemetry output - logs_body_key_attributes does not append to existing log attributes

[ryn9]

Bug Report

Describe the bug When using opentelemetry output, the option logs_body_key_attributes does not append to existing log attributes

To Reproduce Try this config:

service:
  flush: 1
  daemon: off
  log_level: warn
  http_server: off

pipeline:
  inputs:
    - name: opentelemetry
      port: 4318
      logs_body_key: body
      processors:
        logs:
          - name: lua
            match: "*"
            time_as_table: true
            script: scripts/add_test_field.lua
            call: add_test_field
  outputs:
    - name: stdout
      match: "*"
      format: json_lines
    - name: opentelemetry
      match: "*"
      host: otel-collector
      port: 4318
      retry_limit: false
      log_response_payload: false
      tls: off
      tls.verify: off
      logs_body_key: body
      logs_body_key_attributes: true

add_test_field is defined as:

function add_test_field(tag, timestamp, record)
    record["new_field"] = "This is a new field from Lua"
    return 1, timestamp, record
end

The output to std-out shows the new_field being created. The output to the upstream otel collector is not getting new_field appended to the log attributes

Expected behavior The output to the upstream otel collector should get new_field appended to the log attributes

Your Environment

Version used: 4.0.4 / Branch: lua-add-group-metadata-support Configuration: See above Environment name and version (e.g. Kubernetes? What version?): N/A Server type and version: N/A Operating System and version: N/A Filters and plugins: Lua

Additional context

[ryn9]

My hacky work around for now...

nest all the fields under 'body' and then under the OTEL collector sort it out.

As 'nest' is currently has issues with retaining the metadata, I will perform a nesting operation with lua using the 'lua-add-group-metadata-support' branch. I am not sure when the fix to lua (or other filters) will make it to release. reference: https://github.com/fluent/fluent-bit/issues/10442#issuecomment-2950161595

the lua function:

function nest_under_body(tag, timestamp, record)
    local new_record = {}
    new_record["body"] = record
    return 1, timestamp, new_record
end

on the OTEL collector side:

  transform/nested_body_and_attributes:
    error_mode: ignore
    log_statements:
      - context: log
        statements:
          - set(cache["body"], log.body["body"])
          - delete_key(log.body, "body")
          - merge_maps(attributes, log.body, "upsert")
          - set(log.body, cache["body"])
          - delete_key(cache, "body")

[edsiper]

Lua fix was already merged, release will be mid next week

[ryn9]

Thank you so much for quickly looking at these issues! Please let me know if you need me to provide any additional clarity to to comments.

[KoushikBSK]

Eagerly waiting for this release with #10444 fix, as soon as it is out I will be using it in my environment :)

[ryn9]

For clarity - this reported issue does not actually have anything to do with the lua filter specifically.

What I am calling out is that the opentelemetry output logs_body_key_attributes does not append to existing log attributes.

That is - if there are already log attributes in the envelopte/metadata, the logs_body_key_attributes does not appear to do anything.

[KoushikBSK]

Yes I agree (have no interest on logs_body_key_attributes ) and I was mainly highlighting (@edsiper )Eduardo's comment about the release time being this week :) I am keenly waiting to get the new realease with the lua fix to test in my environment.

[edsiper]

Fix: https://github.com/fluent/fluent-bit/pull/10562