From 91766999418eb63c52c94ce44e0f10cb8481e2db Mon Sep 17 00:00:00 2001
From: Paul Bellamy <paul.a.bellamy@gmail.com>
Date: Thu, 12 Nov 2015 13:01:02 +0000
Subject: [PATCH 1/2] omit metric first/last timestamps if they are zero

---
 report/metrics.go | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/report/metrics.go b/report/metrics.go
index b8ae93c4f..3d8711ae0 100644
--- a/report/metrics.go
+++ b/report/metrics.go
@@ -205,11 +205,23 @@ func (m Metric) LastSample() *Sample {
 
 // WireMetrics is the on-the-wire representation of Metrics.
 type WireMetrics struct {
-	Samples []Sample  `json:"samples"` // On the wire, samples are sorted oldest to newest,
-	Min     float64   `json:"min"`     // the opposite order to how we store them internally.
-	Max     float64   `json:"max"`
-	First   time.Time `json:"first"`
-	Last    time.Time `json:"last"`
+	Samples []Sample `json:"samples"` // On the wire, samples are sorted oldest to newest,
+	Min     float64  `json:"min"`     // the opposite order to how we store them internally.
+	Max     float64  `json:"max"`
+	First   string   `json:"first,omitempty"`
+	Last    string   `json:"last,omitempty"`
+}
+
+func renderTime(t time.Time) string {
+	if t.IsZero() {
+		return ""
+	}
+	return t.Format(time.RFC3339Nano)
+}
+
+func parseTime(s string) time.Time {
+	t, _ := time.Parse(time.RFC3339Nano, s)
+	return t
 }
 
 func (m Metric) toIntermediate() WireMetrics {
@@ -223,8 +235,8 @@ func (m Metric) toIntermediate() WireMetrics {
 		Samples: samples,
 		Max:     m.Max,
 		Min:     m.Min,
-		First:   m.First,
-		Last:    m.Last,
+		First:   renderTime(m.First),
+		Last:    renderTime(m.Last),
 	}
 }
 
@@ -237,8 +249,8 @@ func (m WireMetrics) fromIntermediate() Metric {
 		Samples: samples,
 		Max:     m.Max,
 		Min:     m.Min,
-		First:   m.First,
-		Last:    m.Last,
+		First:   parseTime(m.First),
+		Last:    parseTime(m.Last),
 	}
 }
 

From 5dcd53e24cffe6b629d5f21a021d4d13599db48d Mon Sep 17 00:00:00 2001
From: Paul Bellamy <paul.a.bellamy@gmail.com>
Date: Thu, 12 Nov 2015 13:01:20 +0000
Subject: [PATCH 2/2] fix bug in metrics first/last calculation if second arg
 was zero

---
 report/metrics.go               |  4 ++--
 report/metrics_internal_test.go | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 report/metrics_internal_test.go

diff --git a/report/metrics.go b/report/metrics.go
index 3d8711ae0..144f0c74f 100644
--- a/report/metrics.go
+++ b/report/metrics.go
@@ -79,14 +79,14 @@ func (m Metric) Len() int {
 }
 
 func first(t1, t2 time.Time) time.Time {
-	if !t1.IsZero() && t1.Before(t2) {
+	if t2.IsZero() || (!t1.IsZero() && t1.Before(t2)) {
 		return t1
 	}
 	return t2
 }
 
 func last(t1, t2 time.Time) time.Time {
-	if !t1.IsZero() && t1.After(t2) {
+	if t2.IsZero() || (!t1.IsZero() && t1.After(t2)) {
 		return t1
 	}
 	return t2
diff --git a/report/metrics_internal_test.go b/report/metrics_internal_test.go
new file mode 100644
index 000000000..0929ba098
--- /dev/null
+++ b/report/metrics_internal_test.go
@@ -0,0 +1,29 @@
+package report
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFirstLast(t *testing.T) {
+	zero, t1, t2 := time.Time{}, time.Now(), time.Now().Add(1*time.Minute)
+	tests := []struct {
+		arg1, arg2, first, last time.Time
+	}{
+		{zero, zero, zero, zero},
+		{t1, zero, t1, t1},
+		{zero, t1, t1, t1},
+		{t1, t1, t1, t1},
+		{t1, t2, t1, t2},
+		{t2, t1, t1, t2},
+	}
+	for _, test := range tests {
+		if got := first(test.arg1, test.arg2); !got.Equal(test.first) {
+			t.Errorf("first(%q, %q) => %q, Expected: %q", test.arg1, test.arg2, got, test.first)
+		}
+
+		if got := last(test.arg1, test.arg2); !got.Equal(test.last) {
+			t.Errorf("last(%q, %q) => %q, Expected: %q", test.arg1, test.arg2, got, test.last)
+		}
+	}
+}