Shuffle knative.dev/pkg/tracing code a bit (#581)

This moves around the code within the tracing package in preparation for adding support for other exporter options.

As the fields changed are all private, this should be a no-op for consumers of this package.

The goal of this change is to make it so that no files mention zipkin other than zipkin.go (or tests, which I left alone).

tracing/opencensus.go

@@ -2,11 +2,9 @@ package tracing
 
 import (
 	"errors"
+	"io"
 	"sync"
 
-	"contrib.go.opencensus.io/exporter/zipkin"
-	zipkinmodel "github.com/openzipkin/zipkin-go/model"
-	zipkinreporter "github.com/openzipkin/zipkin-go/reporter"
 	"go.opencensus.io/trace"
 
 	"knative.dev/pkg/tracing/config"
@@ -17,10 +15,11 @@ type ConfigOption func(*config.Config)
 
 // OpenCensusTracer is responsible for managing and updating configuration of OpenCensus tracing
 type OpenCensusTracer struct {
-	curCfg         *config.Config
-	configOptions  []ConfigOption
-	zipkinReporter zipkinreporter.Reporter
-	zipkinExporter trace.Exporter
+	curCfg        *config.Config
+	configOptions []ConfigOption
+
+	closer   io.Closer
+	exporter trace.Exporter
 }
 
 // OpenCensus tracing keeps state in globals and therefore we can only run one OpenCensusTracer
@@ -100,38 +99,3 @@ func createOCTConfig(cfg *config.Config) *trace.Config {
 
 	return &octCfg
 }
-
-func WithZipkinExporter(reporterFact ZipkinReporterFactory, endpoint *zipkinmodel.Endpoint) ConfigOption {
-	return func(cfg *config.Config) {
-		var (
-			reporter zipkinreporter.Reporter
-			exporter trace.Exporter
-		)
-
-		if cfg != nil && cfg.Enable {
-			// Initialize our reporter / exporter
-			// do this before cleanup to minimize time where we have duplicate exporters
-			reporter, err := reporterFact(cfg)
-			if err != nil {
-				// TODO(greghaynes) log this error
-				return
-			}
-			exporter := zipkin.NewExporter(reporter, endpoint)
-			trace.RegisterExporter(exporter)
-		}
-
-		// We know this is set because we are called with acquireGlobal lock held
-		oct := globalOct
-		if oct.zipkinExporter != nil {
-			trace.UnregisterExporter(oct.zipkinExporter)
-		}
-
-		if oct.zipkinReporter != nil {
-			// TODO(greghaynes) log this error
-			_ = oct.zipkinReporter.Close()
-		}
-
-		oct.zipkinReporter = reporter
-		oct.zipkinExporter = exporter
-	}
-}

tracing/zipkin.go

@@ -17,8 +17,11 @@ limitations under the License.
 package tracing
 
 import (
+	"contrib.go.opencensus.io/exporter/zipkin"
+	zipkinmodel "github.com/openzipkin/zipkin-go/model"
 	zipkinreporter "github.com/openzipkin/zipkin-go/reporter"
 	httpreporter "github.com/openzipkin/zipkin-go/reporter/http"
+	"go.opencensus.io/trace"
 
 	"knative.dev/pkg/tracing/config"
 )
@@ -34,3 +37,38 @@ func CreateZipkinReporter(cfg *config.Config) (zipkinreporter.Reporter, error) {
 	}
 	return httpreporter.NewReporter(cfg.ZipkinEndpoint), nil
 }
+
+func WithZipkinExporter(reporterFact ZipkinReporterFactory, endpoint *zipkinmodel.Endpoint) ConfigOption {
+	return func(cfg *config.Config) {
+		var (
+			reporter zipkinreporter.Reporter
+			exporter trace.Exporter
+		)
+
+		if cfg != nil && cfg.Enable {
+			// Initialize our reporter / exporter
+			// do this before cleanup to minimize time where we have duplicate exporters
+			reporter, err := reporterFact(cfg)
+			if err != nil {
+				// TODO(greghaynes) log this error
+				return
+			}
+			exporter := zipkin.NewExporter(reporter, endpoint)
+			trace.RegisterExporter(exporter)
+		}
+
+		// We know this is set because we are called with acquireGlobal lock held
+		oct := globalOct
+		if oct.exporter != nil {
+			trace.UnregisterExporter(oct.exporter)
+		}
+
+		if oct.closer != nil {
+			// TODO(greghaynes) log this error
+			_ = oct.closer.Close()
+		}
+
+		oct.closer = reporter
+		oct.exporter = exporter
+	}
+}