"proto: wrong wireType = 2 for field LinkIndex" error after updating to v0.136.0

[martincostello]

Component(s)

No response

What happened?

Describe the bug

Updating from v0.135.0 to v0.136.0 (grafana/docker-otel-lgtm#780), acceptance tests we have for use of the OTel Collector are failing to submit profiles with the following error:

Request failed: rpc error: code = Internal desc = grpc: error unmarshalling request: proto: wrong wireType = 2 for field LinkIndex

The error message appears to be similar to #13727 which was affecting .NET metrics, but in this case the failure is with profiles for an application using opentelemetry-ebpf-profiler.

Steps to reproduce

1. Clone grafana/docker-otel-lgtm@1974826
2. Run scripts/run-acceptance-tests.sh

What did you expect to see?

Profiles are ingested.

What did you see instead?

Profiles are rejected with the error above.

Collector version

v0.136.0

Environment information

Environment

OS: Ubuntu 24.04
Compiler(if manually compiled): N/A

OpenTelemetry Collector configuration

receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317
      http:
        endpoint: 0.0.0.0:4318
        cors:
          allowed_origins:
            - http://*
  prometheus/collector:
    config:
      scrape_configs:
        - job_name: "opentelemetry-collector"
          scrape_interval: 1s
          static_configs:
            - targets: ["127.0.0.1:8888"]

extensions:
  health_check:
    endpoint: 0.0.0.0:13133
    path: "/ready"

processors:
  batch:

exporters:
  otlphttp/metrics:
    endpoint: http://127.0.0.1:9090/api/v1/otlp
    tls:
      insecure: true
  otlphttp/traces:
    endpoint: http://127.0.0.1:4418
    tls:
      insecure: true
  otlphttp/logs:
    endpoint: http://127.0.0.1:3100/otlp
    tls:
      insecure: true
  otlp/profiles:
    endpoint: http://127.0.0.1:4040
    tls:
      insecure: true
  debug/metrics:
    verbosity: detailed
  debug/traces:
    verbosity: detailed
  debug/logs:
    verbosity: detailed

service:
  extensions: [health_check]
  pipelines:
    traces:
      receivers: [otlp]
      processors: [batch]
      exporters: [otlphttp/traces]
      #exporters: [otlphttp/traces,debug/traces]
    metrics:
      receivers: [otlp, prometheus/collector]
      processors: [batch]
      exporters: [otlphttp/metrics]
      #exporters: [otlphttp/metrics,debug/metrics]
    logs:
      receivers: [otlp]
      processors: [batch]
      exporters: [otlphttp/logs]
      #exporters: [otlphttp/logs,debug/logs]
    profiles:
      receivers: [otlp]
      exporters: [otlp/profiles]

Log output

Additional context

No response

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[dmathieu]

Did you upgrade ebpf-profiler to its latest version?
The profiles protocol had breaking changes in this last collector release. The latest version of ebpf-profiler handles them, but you need to upgrade.

[martincostello]

We haven't, no, but I can look to update it manually and see what happens.

I didn't see anything in the release notes about any breaking changes.

[martincostello]

So I tried updating to the latest profiler here grafana/docker-otel-lgtm@c642fd6. That's made the error go away, but the tests are still failing as they don't appear to be able to find the profiling data.

This is what we're querying for:

- query: 'process_cpu:cpu:nanoseconds:cpu:nanoseconds{process_executable_name=~"rolldice"}'
  flamebearers:
    contains: "main.rolldice"

With v0.135.0 we get this response:

2025/09/24 04:14:57 INFO query process_cpu:cpu:nanoseconds:cpu:nanoseconds{process_executable_name=~"rolldice"} response {"version":1,"flamebearer":{"names":["total","net/http.serverHandler.ServeHTTP","entry_SYSCALL_64_after_hwframe","/usr/local/go/src/time/time.go","crypto/internal/fips140/aes/gcm.gcmAesDec","encoding/json/encode.go","/usr/local/go/src/runtime/time.go","main.rolldice","/usr/local/go/src/runtime/sys_linux_amd64.s","regexp/exec.go","regexp.(*machine).step","linux-vdso.1.so","cpu","count","encoding/json.(*encodeState).reflectValue","/usr/local/go/src/runtime/time_nofake.go"],"levels":[[0,1400000000,0,0],[0,900000000,900000000,14,0,500000000,0,1],[900000000,500000000,0,2],[900000000,500000000,0,3],[900000000,500000000,0,4],[900000000,500000000,0,5],[900000000,500000000,0,6],[900000000,500000000,0,7],[900000000,500000000,0,8],[900000000,500000000,0,5],[900000000,500000000,0,9],[900000000,500000000,0,5],[900000000,500000000,0,10],[900000000,450000000,0,12,0,50000000,50000000,11],[900000000,10000000..

with v0.136.0 and the updated profiler we get this reponse:

2025/09/24 13:05:09 INFO query process_cpu:cpu:nanoseconds:cpu:nanoseconds{process_executable_name=~"rolldice"} response {"version":1,"flamebearer":{"names":["total"],"levels":[[0,0,0,0]],"numTicks":0,"maxSelf":0},"metadata":{"format":"single","spyName":"","sampleRate":1000000000,"units":"samples","name":"cpu"},"timeline":{"startTime":1758719040,"samples":[0,0,0,0],"durationDelta":15,"watermarks":null},"groups":null,"heatmap":null}

[dmathieu]

https://github.com/open-telemetry/opentelemetry-collector/blob/main/CHANGELOG-API.md

pdata/pprofile: Upgrade the OTLP protobuf definitions to version 1.8.0 (#13758, #13825, #13839)
pdata/pprofile: Remove deprecated ProfilesDictionary method (#13858)

[dmathieu]

Please open an issue against the proper component.

[martincostello]

Ah - that's not in the CHANGELOG here though.

Please open an issue against the proper component.

What is the proper component?

[dmathieu]

The contrib component you're using with that OTTL query.

[martincostello]

open-telemetry/opentelemetry-collector-contrib#42902