AddOtlpExporter never sends data to Collector

[SpirTBBX]

Hello everyone.

I've got a little problem while using OpenTelemetry on my app C# app (with EF Core and WebAPI).

Environment:

• C# app on windows (using .net 7)
• Containers running on WSL2 Ubuntu VM with network mirrored mode.
• CSPROJ:

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net7.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="7.0.19" />
    <PackageReference Include="OpenTelemetry" Version="1.11.1" />
    <PackageReference Include="OpenTelemetry.Exporter.Console" Version="1.11.1" />
    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.11.1" />
    <PackageReference Include="OpenTelemetry.Exporter.Prometheus.AspNetCore" Version="1.9.0-beta.2" />
    <PackageReference Include="OpenTelemetry.Exporter.Zipkin" Version="1.11.1" />
    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.11.1" />
    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.11.0" />
    <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.11.0" />
    <PackageReference Include="Serilog.Sinks.Grafana.Loki" Version="8.3.0" />
    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.5.0" />
  </ItemGroup>

  <ItemGroup>
    <Folder Include="Logs\" />
  </ItemGroup>

</Project>

I've configured the app to export the data to Otlp collector (running on docker) like this:

builder.Services.AddOpenTelemetry()
    .WithTracing(tracerProviderBuilder =>
    {
        tracerProviderBuilder
            .SetResourceBuilder(resourceBuilder)
            .AddAspNetCoreInstrumentation()
            .AddHttpClientInstrumentation();

        foreach (var source in activitySources)
        {
            tracerProviderBuilder.AddSource(source);
        }

        tracerProviderBuilder.AddConsoleExporter();

        tracerProviderBuilder.AddOtlpExporter(options => 
        {
            options.Endpoint = new Uri("http://localhost:4318/v1/traces");
            options.Protocol = OtlpExportProtocol.HttpProtobuf;
        });
    })

Collector config:

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

exporters:
  debug:
    verbosity: detailed
  zipkin:
    endpoint: "http://172.17.0.1:9411/api/v2/spans"
    tls:
      insecure: true
  otlphttp/loki:
    endpoint: "http://172.17.0.1:3100/otlp"
    tls:
      insecure: true
  otlphttp/zipkin:
    endpoint: "http://172.17.0.1:9411"
    tls:
      insecure: true

service:
  pipelines:
    logs:
      receivers: [otlp]
      exporters: [debug, otlphttp/loki]
    traces:
      receivers: [otlp]
      exporters: [debug, zipkin, otlphttp/zipkin]

I've left the docker compose file attached to the message, in case somebody needs to look at it.

Anyways, using wireshark, on the wsl2 vm, I can't capture any traffic with a POST to /v1/traces

However, if I change from OtlpExporter to ZipkinExporter and leave the OTLP Collector address and path there, I can see a /v1/traces request but I get a 400 BAD Request response (from C# app to the Collector Container). If the address of ZipKin exporter on the C# app is http://localhost:9411/api/v2/spans, it works fine.

From what I've understood so far, based on my testings:
Cases:

• OtlpExporter with http://localhost:4318/v1/traces doesn't show logs on the otel-collector and there's no traffic on wireshark
• ZipKin exporter with the above url shows traffic and the collector replies with 400 bad request
• ZipKin exporter with http://localhost:9411/api/v2/spans works like a charm (since the app on windows sends directly to zipkin)
• Making a request, directly from the C# app, using HttpClient to http://localhost:4318/v1/traces, with content type json and a well-formatted body, allows collector to receive the data.

Attempts with other envs:

• I've attempted to run the collector on windows (in case it could be a networking issue) but got the same behaviour.

Docker compose file:

services:
  zipkin:
    image: openzipkin/zipkin
    container_name: zipkin
    ports:
      - "9411:9411"
    user: "1000:1000"
    environment:
      - MYSQL_DB=zipkin
      - MYSQL_USER=zipkin
      - MYSQL_HOST=172.17.0.1
      - MYSQL_PASS=zipkin
      - STORAGE_TYPE=mysql
  grafana:
    image: grafana/grafana
    container_name: grafana
    ports:
      - "3000:3000"
    volumes:
      - ./grafana-data:/var/lib/grafana
    environment:
      - GF_SECURITY_ADMIN_PASSWORD=admin
    user: "1000:1000"
  loki:
    image: grafana/loki:latest
    container_name: loki
    ports:
      - "3100:3100"
    command: -config.file=/etc/loki/local-config.yaml
    volumes:
      - ./loki-config/local-config.yaml:/etc/loki/local-config.yaml
      - ./loki-data:/tmp/loki
    user: "1000:1000"
  prometheus:
    image: prom/prometheus
    container_name: prometheus
    network_mode: host
#    ports:
#      - "9090:9090"
    volumes:
      - ./prometheus-data:/prometheus
      - ./prometheus-config:/etc/prometheus
    user: "1000:1000"
  otel-collector:
    image: otel/opentelemetry-collector:latest
    container_name: otel-collector
#    network_mode: host
    volumes:
      - ./otlp-config/otel-config.yaml:/etc/otel-config.yaml
    command: [ "--config", "/etc/otel-config.yaml" ]
    ports:
      - "4317:4317"
      - "4318:4318"
    depends_on:
      - loki

[SpirTBBX]

The ZipkinExporter bad request error was fixed by adding a zipkin receiver and by specifying it on the traces receivers' pipeline.

The OtlpExporter, however, doesn't work. Tried with both HTTP & GRPC, with and without the path of /v1/logs