Introducing HTTP Headers to the OTLP Source for Metrics

[sorrowcode]

A note for the community

• Please vote on this issue by adding a 👍 reaction to the original issue to help the community and maintainers prioritize this request
• If you are interested in working on this issue or have submitted a pull request, please leave a comment

Use Cases

Problem:
OTLP metrics source have no possibility to receive headers at the moment. This is currently implemented for logs. In order to streamline the OTLP solution this would be a great feature to make the product more comfortable to use. This header could be used for tenant separation in order to restrict access to vector as a shared component.

Attempted Solutions

No response

Proposal

This could be used similar to the following example implemented for the logs:

transforms:
  "split_with_headers":
    type: remap
    inputs:
      - "otlp.logs"
    source: |
      result = []
      for_each(array!(.resourceLogs)) -> |resource_log_index, resource_log| {
        for_each(array!(resource_log.scopeLogs)) -> |scope_log_index, scope_log| {
          for_each(array!(scope_log.logRecords)) -> |log_record_index, log_record| {
            event = {
              "resourceLogs": [
                resource_log
              ]
            }
            event.resourceLogs[0].scopeLogs = [
              scope_log
            ]
            event.resourceLogs[0].scopeLogs[0].logRecords = [
              log_record
            ]
            event."SomeHeader" = ."SomeHeader"
            result = push(result, event)
          }
        }
      }
      . = result

References

• Example for Logs: opentelemetry source: http headers work only for logs with use_otlp_decoding set to false #24306
• HTTP Headers: https://vector.dev/docs/reference/configuration/sources/opentelemetry/#http.headers
• Logs Only Implementation:

  vector/src/sources/util/http/headers.rs

  Line 27 in 2a8183a

  if let Event::Log(log) = event {

Version

v0.53.0

[RobbieMcKinstry]

Is there a particular reason that headers are only implemented on logs and not traces/metrics? I'm in the same boat -- attempting to support multi-tenancy, but needing to find a workaround because I can't attach tenant identifiers to traces. Thanks for opening this, and thanks for pointing to the relevant source code!

[ozanichkovsky]

@RobbieMcKinstry #24942 solves this by adding the header to metadata (path starts with % instead of . for metadata, like %opentelemetry.headers."Content-Type" in the VRL code to get Content-Type header value).