Support Datadog tracer priority sampling

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/option.go

@@ -1,6 +1,7 @@
 package tracer
 
 import (
+	"net/http"
 	"os"
 	"path/filepath"
 	"time"
@@ -33,6 +34,9 @@ type config struct {
 
 	// propagator propagates span context cross-process
 	propagator Propagator
+
+	// httpRoundTripper defines the http.RoundTripper used by the agent transport.
+	httpRoundTripper http.RoundTripper
 }
 
 // StartOption represents a function that can be provided as a parameter to Start.
@@ -45,6 +49,17 @@ func defaults(c *config) {
 	c.agentAddr = defaultAddress
 }
 
+// WithPrioritySampling is deprecated, and priority sampling is enabled by default.
+// When using distributed tracing, the priority sampling value is propagated in order to
+// get all the parts of a distributed trace sampled.
+// To learn more about priority sampling, please visit:
+// https://docs.datadoghq.com/tracing/getting_further/trace_sampling_and_storage/#priority-sampling-for-distributed-tracing
+func WithPrioritySampling() StartOption {
+	return func(c *config) {
+		// This is now enabled by default.
+	}
+}
+
 // WithDebugMode enables debug mode on the tracer, resulting in more verbose logging.
 func WithDebugMode(enabled bool) StartOption {
 	return func(c *config) {
@@ -93,6 +108,15 @@ func WithSampler(s Sampler) StartOption {
 	}
 }
 
+// WithHTTPRoundTripper allows customizing the underlying HTTP transport for
+// emitting spans. This is useful for advanced customization such as emitting
+// spans to a unix domain socket. The default should be used in most cases.
+func WithHTTPRoundTripper(r http.RoundTripper) StartOption {
+	return func(c *config) {
+		c.httpRoundTripper = r
+	}
+}
+
 // StartSpanOption is a configuration option for StartSpan. It is aliased in order
 // to help godoc group all the functions returning it together. It is considered
 // more correct to refer to it as the type as the origin, ddtrace.StartSpanOption.