Doc and logging

README.md

@@ -54,6 +54,14 @@ Example screenshot of OTEL tracing captured and shown in Jeager UI:
 
 Type `make install-dependencies` to retrieve Go packages needed by the project.
 
+### Configuration
+
+Open telemetry sampling rate can be configured by setting the `OTEL_SAMPLING_RATE`
+environmental variable from 0.0 to 1.0.
+0.0 means no tracing and 1.0 means include all traces.
+Value is measured in percents.
+Therefore 0.5 means 50% of the samples will be collected.
+
 ### Demoing usage
 
 ```bash

docker-compose.yml

@@ -17,16 +17,16 @@ services:
     volumes:
       - ./otel-collector.yaml:/etc/otel-collector.yaml
     ports:
-      - 4317:4317
+      - 127.0.0.1:4317:4317
 
   prometheus:
     image: prom/prometheus:v3.1.0
     volumes:
       - ./prometheus.yaml:/etc/prometheus/prometheus.yml
     ports:
-      - 9090:9090
+      - 127.0.0.1:9090:9090
 
   jaeger:
     image: jaegertracing/all-in-one:1.60
     ports:
-      - 16686:16686
+      - 127.0.0.1:16686:16686

pkg/tracer/otel.go

@@ -142,6 +142,7 @@ func (o *OtelTracerMetrics) defaultTracerProvider(ctx context.Context) error {
 	}
 
 	samplingRate := getSamplerFromEnv()
+	l.Logger.Info().Msgf("Set OTEL sampling rate to %.2f", samplingRate)
 
 	// Register the trace exporter with a TracerProvider, using a batch
 	// span processor to aggregate spans before export.