fix(tracing): set service version (#290)

We were previously only setting the lambda "version" in our
instrumentation version. In practice this instrumentation is only
present in our cold start trace (`realInit`). Other traces will use
tracers belonging to different instrumentation libraries.

This commit introduces `service.version` as part of the resource
attributes. Since the binary is rebuilt on cloudformation template
changes, it should accurately track the version of the service rather
than merely the "binary" version.

tracing/tracing.go

@@ -6,14 +6,19 @@ import (
 	"net/url"
 	"os"
 
+	"github.com/observeinc/aws-sam-apps/version"
+
 	"github.com/go-logr/logr"
 	"go.opentelemetry.io/contrib/detectors/aws/lambda"
 	"go.opentelemetry.io/contrib/exporters/autoexport"
 	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/sdk/resource"
 	"go.opentelemetry.io/otel/sdk/trace"
 )
 
+var serviceVersionKey = attribute.Key("service.version")
+
 func SetLogger(logger logr.Logger) {
 	otel.SetLogger(logger)
 }
@@ -51,6 +56,7 @@ func NewTracerProvider(ctx context.Context) (*trace.TracerProvider, error) {
 	}
 
 	options := []resource.Option{
+		resource.WithAttributes(serviceVersionKey.String(version.Version)),
 		resource.WithFromEnv(),
 	}
 	if os.Getenv("AWS_LAMBDA_FUNCTION_NAME") != "" {