Add tracing spans to app

Also log things like number of nodes in Map, total number of reports.

render/render.go

@@ -3,6 +3,9 @@ package render
 import (
 	"context"
 
+	opentracing "github.com/opentracing/opentracing-go"
+	otlog "github.com/opentracing/opentracing-go/log"
+
 	"github.com/weaveworks/scope/report"
 )
 
@@ -51,6 +54,8 @@ func (ts Transformers) Transform(nodes Nodes) Nodes {
 
 // Render renders the report and then transforms it
 func Render(ctx context.Context, rpt report.Report, renderer Renderer, transformer Transformer) Nodes {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "Render:"+typeName(renderer))
+	defer span.Finish()
 	return transformer.Transform(renderer.Render(ctx, rpt))
 }
 
@@ -65,6 +70,8 @@ func MakeReduce(renderers ...Renderer) Renderer {
 
 // Render produces a set of Nodes given a Report.
 func (r Reduce) Render(ctx context.Context, rpt report.Report) Nodes {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "Reduce.Render")
+	defer span.Finish()
 	l := len(r)
 	switch l {
 	case 0:
@@ -74,7 +81,9 @@ func (r Reduce) Render(ctx context.Context, rpt report.Report) Nodes {
 	for _, renderer := range r {
 		renderer := renderer // Pike!!
 		go func() {
+			span, ctx := opentracing.StartSpanFromContext(ctx, typeName(renderer))
 			c <- renderer.Render(ctx, rpt)
+			span.Finish()
 		}()
 	}
 	for ; l > 1; l-- {
@@ -101,6 +110,8 @@ func MakeMap(f MapFunc, r Renderer) Renderer {
 // Render transforms a set of Nodes produces by another Renderer.
 // using a map function
 func (m Map) Render(ctx context.Context, rpt report.Report) Nodes {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "Map.Render:"+functionName(m.MapFunc))
+	defer span.Finish()
 	var (
 		input  = m.Renderer.Render(ctx, rpt)
 		output = newJoinResults(nil)
@@ -113,6 +124,8 @@ func (m Map) Render(ctx context.Context, rpt report.Report) Nodes {
 			output.add(inRenderable.ID, outRenderable)
 		}
 	}
+	span.LogFields(otlog.Int("input.nodes", len(input.Nodes)),
+		otlog.Int("ouput.nodes", len(output.nodes)))
 
 	return output.result(input)
 }