# Monitoring NServiceBus endpoints with Jaeger

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Jaeger is a distributed tracing system for monitoring and troubleshooting distributed systems. This sample demonstrates how to export OpenTelemetry traces from NServiceBus-based systems to Jaeger.

## Prerequisites

A Jaeger instance is required to send, process and view OpenTelemetry trace diagnostics. Use the [`All in one` Jaeger container image](https://www.jaegertracing.io/docs/1.53/getting-started/#all-in-one) for development and testing purposes by running the following docker command:

```
$ docker run --name jaeger \
  -e COLLECTOR_OTLP_ENABLED=true \
  -p 16686:16686 \
  -p 4317:4317 \
  -p 4318:4318 \
  jaegertracing/all-in-one:latest
```

With this default configuration, the Jaeger UI will be available at `http://localhost:16686` and the [OTEL Collector](https://opentelemetry.io/docs/collector/) is set up to listen on the default ports: 4317 (gRPC) and 4318 (http).

## Code overview

The sample contains two endpoints. The `Publisher` endpoint publishes events. The `Subscriber` event subscribes to the events and sends replies. To enable tracing and export to Jaeger, the `TraceProvider` for each endpoint has to be configured as follows:

<!-- snippet: jaeger-exporter-configuration -->

```cs
var tracerProvider = Sdk.CreateTracerProviderBuilder()
    .SetResourceBuilder(ResourceBuilder.CreateDefault().AddService(EndpointName))
    .AddSource("NServiceBus.Core*")
    .AddOtlpExporter() // The exporter defaults to gRPC on over port 4317 - https://github.com/open-telemetry/opentelemetry-dotnet/blob/main/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/README.md#otlpexporteroptions
    .Build();
```

<!-- endsnippet -->

NServiceBus must also be configured to enable the OpenTelemetry instrumentation:

<!-- snippet: jaeger-endpoint-configuration -->

```cs
var endpointConfiguration = new EndpointConfiguration(EndpointName);

endpointConfiguration.EnableOpenTelemetry();
```

<!-- endsnippet -->

## Running the sample

Run the sample and press <kbd>1</kbd> on the `Publisher` endpoint to publish one or more events. Navigate to the Jaeger UI (at `http://localhost:16686`) to inspect the captured traces:

![jaeger search UI](jaeger-search-view.png)

Inspecting a selected trace shows the conversation flow between the `Publisher` and the `Subscriber` endpoint:

![jaeger trace UI](jaeger-trace-view.png)