traceparent header from incoming http request not propagated to span context

[ncoiffier-celonis]

Describe the bug

It seems that OpenTelemetry traces don't inherit the Span parent ID from the http request (traceparent header).

Steps to reproduce (if applicable)

Tl,dr: on a running quickwit instance, call the /api/v1/_elastic/{indexId}/_search http endpoint with a traceparent header, and observe that the associated root_search span doesn't have a parent ID.

More specifically, using this minimal docker compose:

docker-compose.yaml

services:
  otel-collector:
    image: otel/opentelemetry-collector-contrib:0.119.0
    volumes:
      - ./otel-collector-config.yaml:/etc/otel/config.yaml
    command: ["--config", "/etc/otel/config.yaml"]
    ports:
      - 4317:4317
      - 4318:4318

  quickwit:
    image: quickwit/quickwit:edge
    volumes:
      - qwdata:/quickwit/qwdata
    ports:
      - 7280:7280
    environment:
      - QW_ENABLE_OPENTELEMETRY_OTLP_EXPORTER=true
      - OTEL_EXPORTER_OTLP_ENDPOINT=http://otel-collector:4317
      - OTEL_TRACES_SAMPLER=always_on
    depends_on:
      - otel-collector
    command: ["run"]

  test-client:
    image: curlimages/curl:latest
    depends_on:
      - quickwit
    # Wait for Quickwit to be ready, send one request with a well-known traceparent,
    # then sleep to allow the OTLP batch exporter to flush before the container exits.
    entrypoint:
      - sh
      - -c
      - |
        until curl -sf http://quickwit:7280/health/livez; do sleep 1; done
        curl -sf http://quickwit:7280/api/v1/_elastic/otel-traces-v0_9/_search \
          -H 'Content-Type: application/json' \
          -H 'traceparent: 00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01' \
          -d '{"query":{"match_all":{}},"size":1}'
        sleep 15

volumes:
  qwdata:

otel-collector-config.yaml

receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317
      http:
        endpoint: 0.0.0.0:4318

exporters:
  debug:
    verbosity: detailed

service:
  pipelines:
    traces:
      receivers: [otlp]
      exporters: [debug]
    logs:
      receivers: [otlp]
      exporters: [debug]
    metrics:
      receivers: [otlp]
      exporters: [debug]

I can see the following span:

Span #9
    Trace ID       : 9a66a9922558a74ccd7bc36d01cd25c3
    Parent ID      : 
    ID             : 34136b5bd0bb77ac
    Name           : root_search
    Kind           : Internal
    Start time     : 2026-03-26 10:22:21.380716543 +0000 UTC
    End time       : 2026-03-26 10:22:21.409089709 +0000 UTC
    Status code    : Unset
    Status message : 
Attributes:
     -> code.file.path: Str(quickwit-search/src/root.rs)
     -> code.module.name: Str(quickwit_search::root)
     -> code.line.number: Int(1200)
     -> thread.id: Int(5)
     -> thread.name: Str(main_runtime_thread)
     -> target: Str(quickwit_search::root)
     -> busy_ns: Int(27969792)
     -> idle_ns: Int(404000)
Events:
SpanEvent #0
     -> Name: root_search
     -> Timestamp: 2026-03-26 10:22:21.390622376 +0000 UTC
     -> DroppedAttributesCount: 0
     -> Attributes::
          -> level: Str(INFO)
          -> target: Str(quickwit_search::root)
          -> query_ast: Str({"type":"match_all"})
          -> agg: Str()
          -> start_ts: Str(0..0)
          -> count_required: Str(UNDERESTIMATE)
          -> num_docs: Str(0)
          -> num_splits: Str(0)
          -> code.file.path: Str(quickwit-search/src/root.rs)
          -> code.module.name: Str(quickwit_search::root)
          -> code.line.number: Int(1222)

Expected behavior

Span #9 Parent ID should be should not be null.

Configuration:

Quickwit version: quickwit version: 0.8.0 (aarch64-unknown-linux-gnu 2026-03-11T13:17:37Z 92a526b)