Omit Failcnt in json

I don't see why this should be special, it feels wired in some
stat sections such as kernel memory and swap memory which have
only Failcnt with 0 value.

And this also added unit test cases for failcnt and oom control.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

Author: hqhq

libcontainer/cgroups/fs/memory_test.go

@@ -12,9 +12,11 @@ import (
 const (
 	memoryStatContents = `cache 512
 rss 1024`
-	memoryUsageContents    = "2048\n"
-	memoryMaxUsageContents = "4096\n"
-	memoryFailcnt          = "100\n"
+	memoryUsageContents      = "2048\n"
+	memoryMaxUsageContents   = "4096\n"
+	memoryFailcnt            = "100\n"
+	memoryOomControlContents = `oom_kill_disable 1
+under_oom 0`
 )
 
 func TestMemorySetMemory(t *testing.T) {
@@ -173,6 +175,8 @@ func TestMemoryStatsNoStatFile(t *testing.T) {
 	helper.writeFileContents(map[string]string{
 		"memory.usage_in_bytes":     memoryUsageContents,
 		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.failcnt":            memoryFailcnt,
+		"memory.oom_control":        memoryOomControlContents,
 	})
 
 	memory := &MemoryGroup{}
@@ -189,6 +193,8 @@ func TestMemoryStatsNoUsageFile(t *testing.T) {
 	helper.writeFileContents(map[string]string{
 		"memory.stat":               memoryStatContents,
 		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.failcnt":            memoryFailcnt,
+		"memory.oom_control":        memoryOomControlContents,
 	})
 
 	memory := &MemoryGroup{}
@@ -205,6 +211,8 @@ func TestMemoryStatsNoMaxUsageFile(t *testing.T) {
 	helper.writeFileContents(map[string]string{
 		"memory.stat":           memoryStatContents,
 		"memory.usage_in_bytes": memoryUsageContents,
+		"memory.failcnt":        memoryFailcnt,
+		"memory.oom_control":    memoryOomControlContents,
 	})
 
 	memory := &MemoryGroup{}
@@ -215,13 +223,51 @@ func TestMemoryStatsNoMaxUsageFile(t *testing.T) {
 	}
 }
 
+func TestMemoryStatsNoFailcntFile(t *testing.T) {
+	helper := NewCgroupTestUtil("memory", t)
+	defer helper.cleanup()
+	helper.writeFileContents(map[string]string{
+		"memory.stat":               memoryStatContents,
+		"memory.usage_in_bytes":     memoryUsageContents,
+		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.oom_control":        memoryOomControlContents,
+	})
+
+	memory := &MemoryGroup{}
+	actualStats := *cgroups.NewStats()
+	err := memory.GetStats(helper.CgroupPath, &actualStats)
+	if err == nil {
+		t.Fatal("Expected failure")
+	}
+}
+
+func TestMemoryStatsNoOomControlFile(t *testing.T) {
+	helper := NewCgroupTestUtil("memory", t)
+	defer helper.cleanup()
+	helper.writeFileContents(map[string]string{
+		"memory.stat":               memoryStatContents,
+		"memory.usage_in_bytes":     memoryUsageContents,
+		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.failcnt":            memoryFailcnt,
+	})
+
+	memory := &MemoryGroup{}
+	actualStats := *cgroups.NewStats()
+	err := memory.GetStats(helper.CgroupPath, &actualStats)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestMemoryStatsBadStatFile(t *testing.T) {
 	helper := NewCgroupTestUtil("memory", t)
 	defer helper.cleanup()
 	helper.writeFileContents(map[string]string{
 		"memory.stat":               "rss rss",
 		"memory.usage_in_bytes":     memoryUsageContents,
 		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.failcnt":            memoryFailcnt,
+		"memory.oom_control":        memoryOomControlContents,
 	})
 
 	memory := &MemoryGroup{}
@@ -239,6 +285,8 @@ func TestMemoryStatsBadUsageFile(t *testing.T) {
 		"memory.stat":               memoryStatContents,
 		"memory.usage_in_bytes":     "bad",
 		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.failcnt":            memoryFailcnt,
+		"memory.oom_control":        memoryOomControlContents,
 	})
 
 	memory := &MemoryGroup{}
@@ -256,6 +304,46 @@ func TestMemoryStatsBadMaxUsageFile(t *testing.T) {
 		"memory.stat":               memoryStatContents,
 		"memory.usage_in_bytes":     memoryUsageContents,
 		"memory.max_usage_in_bytes": "bad",
+		"memory.failcnt":            memoryFailcnt,
+		"memory.oom_control":        memoryOomControlContents,
+	})
+
+	memory := &MemoryGroup{}
+	actualStats := *cgroups.NewStats()
+	err := memory.GetStats(helper.CgroupPath, &actualStats)
+	if err == nil {
+		t.Fatal("Expected failure")
+	}
+}
+
+func TestMemoryStatsBadFailcntFile(t *testing.T) {
+	helper := NewCgroupTestUtil("memory", t)
+	defer helper.cleanup()
+	helper.writeFileContents(map[string]string{
+		"memory.stat":               memoryStatContents,
+		"memory.usage_in_bytes":     memoryUsageContents,
+		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.failcnt":            "bad",
+		"memory.oom_control":        memoryOomControlContents,
+	})
+
+	memory := &MemoryGroup{}
+	actualStats := *cgroups.NewStats()
+	err := memory.GetStats(helper.CgroupPath, &actualStats)
+	if err == nil {
+		t.Fatal("Expected failure")
+	}
+}
+
+func TestMemoryStatsBadOomControlFile(t *testing.T) {
+	helper := NewCgroupTestUtil("memory", t)
+	defer helper.cleanup()
+	helper.writeFileContents(map[string]string{
+		"memory.stat":               memoryStatContents,
+		"memory.usage_in_bytes":     memoryUsageContents,
+		"memory.max_usage_in_bytes": memoryMaxUsageContents,
+		"memory.failcnt":            memoryFailcnt,
+		"memory.oom_control":        "bad bad",
 	})
 
 	memory := &MemoryGroup{}

libcontainer/cgroups/stats.go

@@ -35,7 +35,7 @@ type CpuStats struct {
 type MemoryData struct {
 	Usage    uint64 `json:"usage,omitempty"`
 	MaxUsage uint64 `json:"max_usage,omitempty"`
-	Failcnt  uint64 `json:"failcnt"`
+	Failcnt  uint64 `json:"failcnt,omitempty"`
 }
 type MemoryStats struct {
 	// memory used for cache
@@ -77,7 +77,7 @@ type HugetlbStats struct {
 	// maximum usage ever recorded.
 	MaxUsage uint64 `json:"max_usage,omitempty"`
 	// number of times htgetlb usage allocation failure.
-	Failcnt uint64 `json:"failcnt"`
+	Failcnt uint64 `json:"failcnt,omitempty"`
 }
 
 type Stats struct {