#762 enhanced output of example PrintExporter with a focus on clarity (#911)

Author: savaki

README.md

@@ -259,3 +259,4 @@ release in which the functionality was marked *Deprecated*.
 [exporter-xray]: https://github.com/census-ecosystem/opencensus-go-exporter-aws
 [exporter-datadog]: https://github.com/DataDog/opencensus-go-exporter-datadog
 [exporter-graphite]: https://github.com/census-ecosystem/opencensus-go-exporter-graphite
+

examples/exporter/exporter.go

@@ -15,22 +15,91 @@
 package exporter // import "go.opencensus.io/examples/exporter"
 
 import (
-	"log"
+	"encoding/hex"
+	"fmt"
+	"regexp"
+	"time"
 
 	"go.opencensus.io/stats/view"
 	"go.opencensus.io/trace"
 )
 
+// indent these many spaces
+const indent = "  "
+
+// reZero provides a simple way to detect an empty ID
+var reZero = regexp.MustCompile(`^0+$`)
+
 // PrintExporter is a stats and trace exporter that logs
 // the exported data to the console.
+//
+// The intent is help new users familiarize themselves with the
+// capabilities of opencensus.
+//
+// This should NOT be used for production workloads.
 type PrintExporter struct{}
 
 // ExportView logs the view data.
 func (e *PrintExporter) ExportView(vd *view.Data) {
-	log.Println(vd)
+	for _, row := range vd.Rows {
+		fmt.Printf("%v %-45s", vd.End.Format("15:04:05"), vd.View.Name)
+
+		switch v := row.Data.(type) {
+		case *view.DistributionData:
+			fmt.Printf("distribution: min=%.1f max=%.1f mean=%.1f", v.Min, v.Max, v.Mean)
+		case *view.CountData:
+			fmt.Printf("count:        value=%v", v.Value)
+		case *view.SumData:
+			fmt.Printf("sum:          value=%v", v.Value)
+		case *view.LastValueData:
+			fmt.Printf("last:         value=%v", v.Value)
+		}
+		fmt.Println()
+
+		for _, tag := range row.Tags {
+			fmt.Printf("%v- %v=%v\n", indent, tag.Key.Name(), tag.Value)
+		}
+	}
 }
 
 // ExportSpan logs the trace span.
 func (e *PrintExporter) ExportSpan(vd *trace.SpanData) {
-	log.Println(vd)
+	var (
+		traceID      = hex.EncodeToString(vd.SpanContext.TraceID[:])
+		spanID       = hex.EncodeToString(vd.SpanContext.SpanID[:])
+		parentSpanID = hex.EncodeToString(vd.ParentSpanID[:])
+	)
+	fmt.Println()
+	fmt.Println("#----------------------------------------------")
+	fmt.Println()
+	fmt.Println("TraceID:     ", traceID)
+	fmt.Println("SpanID:      ", spanID)
+	if !reZero.MatchString(parentSpanID) {
+		fmt.Println("ParentSpanID:", parentSpanID)
+	}
+
+	fmt.Println()
+	fmt.Printf("Span:    %v\n", vd.Name)
+	fmt.Printf("Status:  %v [%v]\n", vd.Status.Message, vd.Status.Code)
+	fmt.Printf("Elapsed: %v\n", vd.EndTime.Sub(vd.StartTime).Round(time.Millisecond))
+
+	if len(vd.Annotations) > 0 {
+		fmt.Println()
+		fmt.Println("Annotations:")
+		for _, item := range vd.Annotations {
+			fmt.Print(indent, item.Message)
+			for k, v := range item.Attributes {
+				fmt.Printf(" %v=%v", k, v)
+			}
+			fmt.Println()
+		}
+	}
+
+	if len(vd.Attributes) > 0 {
+		fmt.Println()
+		fmt.Println("Attributes:")
+		for k, v := range vd.Attributes {
+			fmt.Printf("%v- %v=%v\n", indent, k, v)
+		}
+	}
 }

examples/http/helloworld_server/main.go

@@ -54,6 +54,13 @@ func main() {
 	http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
 		fmt.Fprintf(w, "hello world")
 
+		// Provide an example of how spans can be annotated with metadata
+		_, span := trace.StartSpan(req.Context(), "child")
+		defer span.End()
+		span.Annotate([]trace.Attribute{trace.StringAttribute("key", "value")}, "something happened")
+		span.AddAttributes(trace.StringAttribute("hello", "world"))
+		time.Sleep(time.Millisecond * 125)
+
 		r, _ := http.NewRequest("GET", "https://example.com", nil)
 
 		// Propagate the trace header info in the outgoing requests.