Add a timestamp on each report saying when it was generated

Not currently used in the code, but useful when troubleshooting.

probe/probe.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/armon/go-metrics"
 	log "github.com/sirupsen/logrus"
+	"github.com/weaveworks/common/mtime"
 	"golang.org/x/time/rate"
 
 	"github.com/weaveworks/scope/report"
@@ -185,6 +186,7 @@ func (p *Probe) report() report.Report {
 	}
 
 	result := report.MakeReport()
+	result.TS = mtime.Now()
 	for i := 0; i < cap(reports); i++ {
 		result.UnsafeMerge(<-reports)
 	}

probe/probe_internal_test.go

@@ -69,6 +69,7 @@ func TestProbe(t *testing.T) {
 	node := report.MakeNodeWith("a", map[string]string{"b": "c"})
 
 	want.Endpoint.AddNode(node)
+	want.TS = now
 
 	pub := mockPublisher{make(chan report.Report, 10)}
 

report/report.go

@@ -85,6 +85,9 @@ var topologyNames = []string{
 // stored by apps. It's composed of multiple topologies, each representing
 // a different (related, but not equivalent) view of the network.
 type Report struct {
+	// TS is the time this report was generated
+	TS time.Time
+
 	// Endpoint nodes are individual (address, port) tuples on each host.
 	// They come from inspecting active connections and can (theoretically)
 	// be traced back to a process. Edges are present.
@@ -321,6 +324,7 @@ func MakeReport() Report {
 // Copy returns a value copy of the report.
 func (r Report) Copy() Report {
 	newReport := Report{
+		TS:       r.TS,
 		DNS:      r.DNS.Copy(),
 		Sampling: r.Sampling,
 		Window:   r.Window,
@@ -336,6 +340,10 @@ func (r Report) Copy() Report {
 
 // UnsafeMerge merges another Report into the receiver. The original is modified.
 func (r *Report) UnsafeMerge(other Report) {
+	// Merged report has the earliest non-zero timestamp
+	if !other.TS.IsZero() && (r.TS.IsZero() || other.TS.Before(r.TS)) {
+		r.TS = other.TS
+	}
 	r.DNS = r.DNS.Merge(other.DNS)
 	r.Sampling = r.Sampling.Merge(other.Sampling)
 	r.Window = r.Window + other.Window