From 900a3f76c8e9e466b9597fe2c1d683999a418f41 Mon Sep 17 00:00:00 2001
From: Nan Deng <dengnan@google.com>
Date: Tue, 24 Jun 2014 16:01:13 -0700
Subject: [PATCH] cpu hot plugging

---
 info/container.go      | 24 ++++++++++-----------
 info/container_test.go | 47 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 12 deletions(-)

diff --git a/info/container.go b/info/container.go
index 7860c9d3..3e2447d9 100644
--- a/info/container.go
+++ b/info/container.go
@@ -119,7 +119,7 @@ type CpuStats struct {
 
 		// Per CPU/core usage of the container.
 		// Unit: nanoseconds.
-		PerCpu []uint64 `json:"per_cpu,omitempty"`
+		PerCpu []uint64 `json:"per_cpu_usage,omitempty"`
 
 		// Time spent in user space.
 		// Unit: nanoseconds
@@ -175,7 +175,7 @@ type ContainerStatsSample struct {
 		Usage uint64 `json:"usage"`
 
 		// Per-core usage of the container. (unit: nanoseconds)
-		PerCpu []uint64 `json:"per_cpu,omitempty"`
+		PerCpuUsage []uint64 `json:"per_cpu_usage,omitempty"`
 	} `json:"cpu"`
 	Memory struct {
 		// Units: Bytes.
@@ -218,24 +218,24 @@ func NewSample(prev, current *ContainerStats) (*ContainerStatsSample, error) {
 	var percpu []uint64
 
 	if len(current.Cpu.Usage.PerCpu) > 0 {
-		if len(current.Cpu.Usage.PerCpu) != len(prev.Cpu.Usage.PerCpu) {
-			return nil, fmt.Errorf("current number of cores is %v; but there are %v cores in previous stats",
-				len(current.Cpu.Usage.PerCpu), len(prev.Cpu.Usage.PerCpu))
-		}
-		percpu = make([]uint64, len(current.Cpu.Usage.PerCpu))
+		curNumCpus := len(current.Cpu.Usage.PerCpu)
+		percpu = make([]uint64, curNumCpus)
 
-		for i, curUsage := range current.Cpu.Usage.PerCpu {
-			prevUsage := prev.Cpu.Usage.PerCpu[i]
-			if curUsage < prevUsage {
+		for i, currUsage := range current.Cpu.Usage.PerCpu {
+			var prevUsage uint64 = 0
+			if i < len(prev.Cpu.Usage.PerCpu) {
+				prevUsage = prev.Cpu.Usage.PerCpu[i]
+			}
+			if currUsage < prevUsage {
 				return nil, fmt.Errorf("current per-core CPU usage is less than prev per-core CPU usage (cumulative).")
 			}
-			percpu[i] = curUsage - prevUsage
+			percpu[i] = currUsage - prevUsage
 		}
 	}
 	sample := new(ContainerStatsSample)
 	// Calculate the diff to get the CPU usage within the time interval.
 	sample.Cpu.Usage = current.Cpu.Usage.Total - prev.Cpu.Usage.Total
-	sample.Cpu.PerCpu = percpu
+	sample.Cpu.PerCpuUsage = percpu
 	// Memory usage is current memory usage
 	sample.Memory.Usage = current.Memory.Usage
 	sample.Timestamp = current.Timestamp
diff --git a/info/container_test.go b/info/container_test.go
index 4b275bec..071ed914 100644
--- a/info/container_test.go
+++ b/info/container_test.go
@@ -230,3 +230,50 @@ func TestAddSampleWrongCpuUsage(t *testing.T) {
 		t.Errorf("generated an unexpected sample: %+v", sample)
 	}
 }
+
+func TestAddSampleHotPluggingCpu(t *testing.T) {
+	cpuPrevUsage := uint64(10)
+	cpuCurrentUsage := uint64(15)
+	memCurrentUsage := uint64(200)
+	prevTime := time.Now()
+
+	prev := createStats(cpuPrevUsage, memCurrentUsage, prevTime)
+	current := createStats(cpuCurrentUsage, memCurrentUsage, prevTime.Add(1*time.Second))
+	current.Cpu.Usage.PerCpu = append(current.Cpu.Usage.PerCpu, 10)
+
+	sample, err := NewSample(prev, current)
+	if err != nil {
+		t.Errorf("should be able to generate a sample. but received error: %v", err)
+	}
+	if len(sample.Cpu.PerCpuUsage) != 2 {
+		t.Fatalf("Should have 2 cores.")
+	}
+	if sample.Cpu.PerCpuUsage[0] != cpuCurrentUsage-cpuPrevUsage {
+		t.Errorf("First cpu usage is %v. should be %v", sample.Cpu.PerCpuUsage[0], cpuCurrentUsage-cpuPrevUsage)
+	}
+	if sample.Cpu.PerCpuUsage[1] != 10 {
+		t.Errorf("Second cpu usage is %v. should be 10", sample.Cpu.PerCpuUsage[1])
+	}
+}
+
+func TestAddSampleHotUnpluggingCpu(t *testing.T) {
+	cpuPrevUsage := uint64(10)
+	cpuCurrentUsage := uint64(15)
+	memCurrentUsage := uint64(200)
+	prevTime := time.Now()
+
+	prev := createStats(cpuPrevUsage, memCurrentUsage, prevTime)
+	current := createStats(cpuCurrentUsage, memCurrentUsage, prevTime.Add(1*time.Second))
+	prev.Cpu.Usage.PerCpu = append(prev.Cpu.Usage.PerCpu, 10)
+
+	sample, err := NewSample(prev, current)
+	if err != nil {
+		t.Errorf("should be able to generate a sample. but received error: %v", err)
+	}
+	if len(sample.Cpu.PerCpuUsage) != 1 {
+		t.Fatalf("Should have 1 cores.")
+	}
+	if sample.Cpu.PerCpuUsage[0] != cpuCurrentUsage-cpuPrevUsage {
+		t.Errorf("First cpu usage is %v. should be %v", sample.Cpu.PerCpuUsage[0], cpuCurrentUsage-cpuPrevUsage)
+	}
+}