Combine constants and reuse port (jaegertracing#415)

Signed-off-by: Yuri Shkuro <ys@uber.com>

constants.go

@@ -14,7 +14,11 @@
 
 package jaeger
 
-import "github.com/opentracing/opentracing-go"
+import (
+	"fmt"
+
+	"github.com/opentracing/opentracing-go"
+)
 
 const (
 	// JaegerClientVersion is the version of the client library reported as Span tag.
@@ -95,3 +99,8 @@ const (
 	// with an already defined context.
 	selfRefType opentracing.SpanReferenceType = 99
 )
+
+var (
+	// DefaultSamplingServerURL is the default url to fetch sampling config from, via http
+	DefaultSamplingServerURL = fmt.Sprintf("http://localhost:%d/sampling", DefaultSamplingServerPort)
+)

sampler.go

@@ -28,7 +28,6 @@ import (
 )
 
 const (
-	defaultSamplingServerURL       = "http://localhost:5778/sampling"
 	defaultSamplingRefreshInterval = time.Minute
 	defaultMaxOperations           = 2000
 )
@@ -435,7 +434,7 @@ func applySamplerOptions(opts ...SamplerOption) samplerOptions {
 		options.maxOperations = defaultMaxOperations
 	}
 	if options.samplingServerURL == "" {
-		options.samplingServerURL = defaultSamplingServerURL
+		options.samplingServerURL = DefaultSamplingServerURL
 	}
 	if options.metrics == nil {
 		options.metrics = NewNullMetrics()