Why won't the OtlpLogExporter send logs to an OTEL endpoint?

[bb-avi]

I've been trying for two days now to get logs to send - without any success.

I am using a barely modified ASP.NET Core Web API .NET 8.0 project.

UPDATE: I'm now using these SDK packages:
OpenTelemetry.Exporter.OpenTelemetry.Protocol v1.13.1
OpenTelemetry.Extensions.Hosting v1.13.1
OpenTelemetry.Instrumentation.AspNetCore v1.13.0
OpenTelemetry.Instrumentation.Http v1.13.0
OpenTelemetry.Instrumentation.Runtime v1.13.0

I have set the default log-level to "Trace"so I can see what is being sent. Logs are being sent to the console. In the console logs I can see metrics and traces being sent to the OTEL endpoint:Start processing HTTP request POST https:///v1/metricsorStart processing HTTP request POST https:///v1/traces`
But the console logs DO NOT show logs being sent to the OTEL endpoint.

I've tried so many variations:

• Using log-specific environment variables with builder.Services.AddOpenTelemetry().UseOtlpExporter()
• Using hard-coded values with builder.Services.AddOpenTelemetry().WithLogging(...
• Using hard-coded values with builder.Services.ConfigureOpenTelemetryLoggerProvider(...
• Using hard-coded values with var loggerFactory = LoggerFactory.Create(logging => logging.AddOpenTelemetry(...

Below is my latest variation that requires the least amount of code to replicate...

Environment variables in the launch configuration (verified these are in the app configuration):

"OTEL_RESOURCE_ATTRIBUTES": "deployment.environment=development,service.version=0.0.1",
"OTEL_SERVICE_NAME": "app-name-here",
"OTEL_EXPORTER_OTLP_LOGS_ENDPOINT": "https://<redacted>/v1/logs",
"OTEL_EXPORTER_OTLP_LOGS_HEADERS": "api-key=<redacted>",
"OTEL_EXPORTER_OTLP_LOGS_PROTOCOL": "http/protobuf",
"OTEL_EXPORTER_OTLP_LOGS_TIMEOUT": "10000",
"OTEL_BLRP_SCHEDULE_DELAY": "10000",
"OTEL_BLRP_EXPORT_TIMEOUT": "5000",
"OTEL_LOG_LEVEL": "debug",
"OTEL_EXPORTER_OTLP_TRACES_ENDPOINT": "https://<redacted>/v1/traces",
"OTEL_EXPORTER_OTLP_TRACES_HEADERS": "api-key=<redacted>",
"OTEL_EXPORTER_OTLP_TRACES_PROTOCOL": "http/protobuf",
"OTEL_EXPORTER_OTLP_TRACES_TIMEOUT": "10000",
"OTEL_TRACES_SAMPLER": "always_on",
"OTEL_BSP_SCHEDULE_DELAY": "1000",
"OTEL_EXPORTER_OTLP_METRICS_ENDPOINT": "https://<redacted>/v1/metrics",
"OTEL_EXPORTER_OTLP_METRICS_HEADERS": "api-key=<redacted>",
"OTEL_EXPORTER_OTLP_METRICS_PROTOCOL": "http/protobuf",
"OTEL_EXPORTER_OTLP_METRICS_TIMEOUT": "10000",
"OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE": "delta",
"OTEL_METRIC_EXPORT_INTERVAL": "10000"

Logging Configuration in appsettings.json:

{
  "Logging": {
    "LogLevel": {
      "Default": "Trace"
    }
  }
}

With this code in Program.cs I only see metrics trying to be sent:

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddOpenTelemetry()
    .UseOtlpExporter()
    .WithLogging(builder => { }, options => { 
        options.IncludeFormattedMessage = true;
        options.ParseStateValues = true;
        options.IncludeScopes = true;
    })
    .WithMetrics(builder => builder.AddRuntimeInstrumentation().AddAspNetCoreInstrumentation().AddHttpClientInstrumentation())
    .WithTracing(builder => builder.AddAspNetCoreInstrumentation().AddHttpClientInstrumentation());

builder.Services.AddHttpClient();

// Basic weather ASPNet API code follows >>>>

These are the types of messages I see in the console log for metrics and traces - - nothing for logs:

System.Net.Http.HttpClient.OtlpMetricExporter.LogicalHandler: Information: Start processing HTTP request POST https://<redacted>/v1/metrics
System.Net.Http.HttpClient.OtlpMetricExporter.LogicalHandler: Trace: Request Headers:
api-key: <redacted>
User-Agent: OTel-OTLP-Exporter-Dotnet/1.13.1
Content-Type: application/x-protobuf

System.Net.Http.HttpClient.OtlpMetricExporter.ClientHandler: Information: Received HTTP response headers after 260.6671ms - 200
System.Net.Http.HttpClient.OtlpMetricExporter.ClientHandler: Trace: Response Headers:
Date: Wed, 12 Nov 2025 20:15:43 GMT
X-Content-Type-Options: nosniff
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
Content-Type: application/x-protobuf
Content-Length: 0

System.Net.Http.HttpClient.OtlpTraceExporter.LogicalHandler: Information: Start processing HTTP request POST https://<redacted>/v1/traces
System.Net.Http.HttpClient.OtlpTraceExporter.LogicalHandler: Trace: Request Headers:
api-key: <redacted>
User-Agent: OTel-OTLP-Exporter-Dotnet/1.13.1
Content-Type: application/x-protobuf

System.Net.Http.HttpClient.OtlpTraceExporter.ClientHandler: Information: Received HTTP response headers after 61.8235ms - 200
System.Net.Http.HttpClient.OtlpTraceExporter.ClientHandler: Trace: Response Headers:
cross-origin-resource-policy: cross-origin
Accept-Encoding: identity,gzip,x-gzip,deflate,x-deflate,zstd
X-Content-Type-Options: nosniff
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
Date: Wed, 12 Nov 2025 20:15:38 GMT
Content-Type: application/json
Content-Length: 0

What am I missing?

[Kielek]

I suppose that you are using GRPC instead of http/protobuf. I would suggest also to upgrade to the latest version of OTel packages.

This one + endoint should be configurable onadd OTLP Exporter options.

[bb-avi]

Thank you for your time.
I had tried newer packages but didn't notice any difference. I will try them again.
As seen in the environment variables above, I'm always using protocol http/protobuf.

[bb-avi]

I upgraded to the following SDKs - - no change.

• OpenTelemetry.Exporter.OpenTelemetry.Protocol v1.13.1
• OpenTelemetry.Extensions.Hosting v1.13.1
• OpenTelemetry.Instrumentation.Runtime v1.13.0

[bb-avi]

My mistake was thinking that when the logs were sent that there would be some log messages saying they were sent - like traces and metrics. But I guess logging that you're sending logs may be a bit redundant.

Once I verified traces, metrics, and logs were successfully sending to our telemetry destination, I went back and set the default log level to Trace. That's when I found that only traces and metrics create log entries when they send - there are no log entries created when the logs send.