Support to handle more than 4 fields in cpuacct.stat

Signed-off-by: Guodong Zhu <guodong9211@gmail.com>

cpuacct.go

@@ -17,8 +17,10 @@
 package cgroups
 
 import (
+	"bufio"
 	"fmt"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -86,36 +88,41 @@ func (c *cpuacctController) percpuUsage(path string) ([]uint64, error) {
 
 func (c *cpuacctController) getUsage(path string) (user uint64, kernel uint64, err error) {
 	statPath := filepath.Join(c.Path(path), "cpuacct.stat")
-	data, err := ioutil.ReadFile(statPath)
+	f, err := os.Open(statPath)
 	if err != nil {
 		return 0, 0, err
 	}
-	fields := strings.Fields(string(data))
-	if len(fields) != 4 {
-		return 0, 0, fmt.Errorf("%q is expected to have 4 fields", statPath)
+	defer f.Close()
+	var (
+		raw = make(map[string]uint64)
+		sc  = bufio.NewScanner(f)
+	)
+	for sc.Scan() {
+		key, v, err := parseKV(sc.Text())
+		if err != nil {
+			return 0, 0, err
+		}
+		raw[key] = v
+	}
+	if err := sc.Err(); err != nil {
+		return 0, 0, err
 	}
 	for _, t := range []struct {
-		index int
 		name  string
 		value *uint64
 	}{
 		{
-			index: 0,
 			name:  "user",
 			value: &user,
 		},
 		{
-			index: 2,
 			name:  "system",
 			value: &kernel,
 		},
 	} {
-		if fields[t.index] != t.name {
-			return 0, 0, fmt.Errorf("expected field %q but found %q in %q", t.name, fields[t.index], statPath)
-		}
-		v, err := strconv.ParseUint(fields[t.index+1], 10, 64)
-		if err != nil {
-			return 0, 0, err
+		v, ok := raw[t.name]
+		if !ok {
+			return 0, 0, fmt.Errorf("expected field %q but not found in %q", t.name, statPath)
 		}
 		*t.value = v
 	}

cpuacct_test.go

@@ -0,0 +1,67 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package cgroups
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+const cpuacctStatData = `user 1
+system 2
+sched_delay 3
+`
+
+func TestGetUsage(t *testing.T) {
+	mock, err := newMock()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer mock.delete()
+	cpuacct := NewCpuacct(mock.root)
+	if cpuacct == nil {
+		t.Fatal("cpuacct is nil")
+	}
+	err = os.Mkdir(filepath.Join(mock.root, string(Cpuacct), "test"), defaultDirPerm)
+	if err != nil {
+		t.Fatal(err)
+	}
+	current := filepath.Join(mock.root, string(Cpuacct), "test", "cpuacct.stat")
+	if err = ioutil.WriteFile(
+		current,
+		[]byte(cpuacctStatData),
+		defaultFilePerm,
+	); err != nil {
+		t.Fatal(err)
+	}
+	user, kernel, err := cpuacct.getUsage("test")
+	if err != nil {
+		t.Fatalf("can't get usage: %v", err)
+	}
+	index := []uint64{
+		user,
+		kernel,
+	}
+	for i, v := range index {
+		expected := ((uint64(i) + 1) * nanosecondsInSecond) / clockTicks
+		if v != expected {
+			t.Errorf("expected value at index %d to be %d but received %d", i, expected, v)
+		}
+	}
+}