Add memory usage and max usage stats.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)

pkg/cgroups/fs/memory.go

@@ -2,6 +2,7 @@ package fs
 
 import (
 	"bufio"
+	"fmt"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -56,13 +57,14 @@ func (s *memoryGroup) Stats(d *data) (map[string]float64, error) {
 		return nil, err
 	}
 
-	f, err := os.Open(filepath.Join(path, "memory.stat"))
+	// Set stats from memory.stat.
+	statsFile, err := os.Open(filepath.Join(path, "memory.stat"))
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	defer statsFile.Close()
 
-	sc := bufio.NewScanner(f)
+	sc := bufio.NewScanner(statsFile)
 	for sc.Scan() {
 		t, v, err := getCgroupParamKeyValue(sc.Text())
 		if err != nil {
@@ -70,5 +72,19 @@ func (s *memoryGroup) Stats(d *data) (map[string]float64, error) {
 		}
 		paramData[t] = v
 	}
+
+	// Set memory usage and max historical usage.
+	params := []string{
+		"usage_in_bytes",
+		"max_usage_in_bytes",
+	}
+	for _, param := range params {
+		value, err := getCgroupParamFloat64(path, fmt.Sprintf("memory.%s", param))
+		if err != nil {
+			return nil, err
+		}
+		paramData[param] = value
+	}
+
 	return paramData, nil
 }

pkg/cgroups/fs/utils.go

@@ -3,6 +3,8 @@ package fs
 import (
 	"errors"
 	"fmt"
+	"io/ioutil"
+	"path/filepath"
 	"strconv"
 	"strings"
 )
@@ -27,3 +29,12 @@ func getCgroupParamKeyValue(t string) (string, float64, error) {
 		return "", 0.0, ErrNotValidFormat
 	}
 }
+
+// Gets a single float64 value from the specified cgroup file.
+func getCgroupParamFloat64(cgroupPath, cgroupFile string) (float64, error) {
+	contents, err := ioutil.ReadFile(filepath.Join(cgroupPath, cgroupFile))
+	if err != nil {
+		return -1.0, err
+	}
+	return strconv.ParseFloat(strings.TrimSpace(string(contents)), 64)
+}

pkg/cgroups/fs/utils_test.go

@@ -0,0 +1,68 @@
+package fs
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+const (
+	cgroupFile  = "cgroup.file"
+	floatValue  = 2048.0
+	floatString = "2048"
+)
+
+func TestGetCgroupParamsFloat64(t *testing.T) {
+	// Setup tempdir.
+	tempDir, err := ioutil.TempDir("", "cgroup_utils_test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tempDir)
+	tempFile := filepath.Join(tempDir, cgroupFile)
+
+	// Success.
+	err = ioutil.WriteFile(tempFile, []byte(floatString), 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	value, err := getCgroupParamFloat64(tempDir, cgroupFile)
+	if err != nil {
+		t.Fatal(err)
+	} else if value != floatValue {
+		t.Fatalf("Expected %f to equal %f", value, floatValue)
+	}
+
+	// Success with new line.
+	err = ioutil.WriteFile(tempFile, []byte(floatString+"\n"), 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	value, err = getCgroupParamFloat64(tempDir, cgroupFile)
+	if err != nil {
+		t.Fatal(err)
+	} else if value != floatValue {
+		t.Fatalf("Expected %f to equal %f", value, floatValue)
+	}
+
+	// Not a float.
+	err = ioutil.WriteFile(tempFile, []byte("not-a-float"), 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = getCgroupParamFloat64(tempDir, cgroupFile)
+	if err == nil {
+		t.Fatal("Expecting error, got none")
+	}
+
+	// Unknown file.
+	err = os.Remove(tempFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = getCgroupParamFloat64(tempDir, cgroupFile)
+	if err == nil {
+		t.Fatal("Expecting error, got none")
+	}
+}