Ensure backward compatilibity in report's node controls

The new probe will convert all node's LatestControls to Controls, so
the old app can consume them. Also, the new app will convert all
node's Controls to LatestControl, so it can consume the reports from
old probes.

app/collector.go

@@ -118,7 +118,9 @@ func (c *collector) Report(_ context.Context) (report.Report, error) {
 	}
 
 	c.clean()
-	return c.merger.Merge(c.reports), nil
+	rpt := c.merger.Merge(c.reports).Upgrade()
+	c.cached = &rpt
+	return rpt, nil
 }
 
 func (c *collector) clean() {

probe/probe.go

@@ -200,7 +200,7 @@ ForLoop:
 		}
 	}
 
-	if err := p.publisher.Publish(rpt); err != nil {
+	if err := p.publisher.Publish(rpt.BackwardCompatible()); err != nil {
 		log.Infof("publish: %v", err)
 	}
 }

report/report.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/weaveworks/scope/common/mtime"
 	"github.com/weaveworks/scope/common/xfer"
 )
 
@@ -254,6 +255,57 @@ func (r Report) Validate() error {
 	return nil
 }
 
+// Upgrade returns a new report based on a report received from the old probe.
+//
+// This for now creates node's LatestControls from Controls.
+func (r Report) Upgrade() Report {
+	cp := r.Copy()
+	ncd := NodeControlData{
+		Dead: false,
+	}
+	cp.WalkTopologies(func(topology *Topology) {
+		n := Nodes{}
+		for name, node := range topology.Nodes {
+			if node.LatestControls.Size() == 0 && len(node.Controls.Controls) > 0 {
+				for _, control := range node.Controls.Controls {
+					node.LatestControls = node.LatestControls.Set(control, node.Controls.Timestamp, ncd)
+				}
+			}
+			n[name] = node
+		}
+		topology.Nodes = n
+	})
+	return cp
+}
+
+// BackwardCompatible returns a new backward-compatible report.
+//
+// This for now creates node's Controls from LatestControls.
+func (r Report) BackwardCompatible() Report {
+	now := mtime.Now()
+	cp := r.Copy()
+	cp.WalkTopologies(func(topology *Topology) {
+		n := Nodes{}
+		for name, node := range topology.Nodes {
+			var controls []string
+			node.LatestControls.ForEach(func(k string, _ time.Time, v NodeControlData) {
+				if !v.Dead {
+					controls = append(controls, k)
+				}
+			})
+			if len(controls) > 0 {
+				node.Controls = NodeControls{
+					Timestamp: now,
+					Controls:  MakeStringSet(controls...),
+				}
+			}
+			n[name] = node
+		}
+		topology.Nodes = n
+	})
+	return cp
+}
+
 // Sampling describes how the packet data sources for this report were
 // sampled. It can be used to calculate effective sample rates. We can't
 // just put the rate here, because that can't be accurately merged. Counts

report/report_test.go

@@ -3,8 +3,12 @@ package report_test
 import (
 	"reflect"
 	"testing"
+	"time"
 
+	"github.com/weaveworks/scope/common/mtime"
 	"github.com/weaveworks/scope/report"
+	"github.com/weaveworks/scope/test"
+	s_reflect "github.com/weaveworks/scope/test/reflect"
 )
 
 func newu64(value uint64) *uint64 { return &value }
@@ -74,3 +78,46 @@ func TestNode(t *testing.T) {
 		}
 	}
 }
+
+func TestReportBackwardCompatibility(t *testing.T) {
+	mtime.NowForce(time.Now())
+	defer mtime.NowReset()
+	rpt := report.MakeReport()
+	controls := map[string]report.NodeControlData{
+		"dead": {
+			Dead: true,
+		},
+		"alive": {
+			Dead: false,
+		},
+	}
+	node := report.MakeNode("foo").WithLatestControls(controls)
+	expectedNode := node.WithControls("alive")
+	rpt.Pod.AddNode(node)
+	expected := report.MakeReport()
+	expected.Pod.AddNode(expectedNode)
+	got := rpt.BackwardCompatible()
+	if !s_reflect.DeepEqual(expected, got) {
+		t.Error(test.Diff(expected, got))
+	}
+}
+
+func TestReportUpgrade(t *testing.T) {
+	mtime.NowForce(time.Now())
+	defer mtime.NowReset()
+	node := report.MakeNode("foo").WithControls("alive")
+	controls := map[string]report.NodeControlData{
+		"alive": {
+			Dead: false,
+		},
+	}
+	expectedNode := node.WithLatestControls(controls)
+	rpt := report.MakeReport()
+	rpt.Pod.AddNode(node)
+	expected := report.MakeReport()
+	expected.Pod.AddNode(expectedNode)
+	got := rpt.Upgrade()
+	if !s_reflect.DeepEqual(expected, got) {
+		t.Error(test.Diff(expected, got))
+	}
+}