[process] Add support for cgroups

process/process.go

@@ -26,6 +26,7 @@ type Process struct {
 	Pid            int32 `json:"pid"`
 	name           string
 	status         string
+	cgroup         string
 	parent         int32
 	parentMutex    sync.RWMutex // for windows ppid cache
 	numCtxSwitches *NumCtxSwitchesStat
@@ -375,6 +376,11 @@ func (p *Process) Name() (string, error) {
 	return p.NameWithContext(context.Background())
 }
 
+// Cgroup returns cgroup of the process.
+func (p *Process) Cgroup() (string, error) {
+	return p.CgroupWithContext(context.Background())
+}
+
 // Exe returns executable path of the process.
 func (p *Process) Exe() (string, error) {
 	return p.ExeWithContext(context.Background())

process/process_darwin.go

@@ -89,6 +89,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return name, nil
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	return "", common.ErrNotImplementedError
+}
+
 func (p *Process) createTimeWithContext(ctx context.Context) (int64, error) {
 	k, err := p.getKProc()
 	if err != nil {

process/process_fallback.go

@@ -50,6 +50,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return "", common.ErrNotImplementedError
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	return "", common.ErrNotImplementedError
+}
+
 func (p *Process) TgidWithContext(ctx context.Context) (int32, error) {
 	return 0, common.ErrNotImplementedError
 }

process/process_freebsd.go

@@ -62,6 +62,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return name, nil
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	return "", common.ErrNotImplementedError
+}
+
 func (p *Process) CwdWithContext(ctx context.Context) (string, error) {
 	return "", common.ErrNotImplementedError
 }

process/process_linux.go

@@ -90,6 +90,15 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return p.name, nil
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	if p.cgroup == "" {
+		if err := p.fillCgroupWithContext(ctx); err != nil {
+			return "", err
+		}
+	}
+	return p.cgroup, nil
+}
+
 func (p *Process) TgidWithContext(ctx context.Context) (int32, error) {
 	if p.tgid == 0 {
 		if err := p.fillFromStatusWithContext(ctx); err != nil {
@@ -810,6 +819,19 @@ func (p *Process) fillFromCommWithContext(ctx context.Context) error {
 	return nil
 }
 
+// Get cgroup from /proc/(pid)/cgroup
+func (p *Process) fillCgroupWithContext(ctx context.Context) error {
+	pid := p.Pid
+	statPath := common.HostProcWithContext(ctx, strconv.Itoa(int(pid)), "cgroup")
+	contents, err := os.ReadFile(statPath)
+	if err != nil {
+		return err
+	}
+
+	p.cgroup = strings.TrimSuffix(string(contents), "\n")
+	return nil
+}
+
 // Get various status from /proc/(pid)/status
 func (p *Process) fillFromStatus() error {
 	return p.fillFromStatusWithContext(context.Background())

process/process_openbsd.go

@@ -67,6 +67,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return name, nil
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	return "", nil
+}
+
 func (p *Process) CwdWithContext(ctx context.Context) (string, error) {
 	return "", common.ErrNotImplementedError
 }

process/process_plan9.go

@@ -50,6 +50,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return "", common.ErrNotImplementedError
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	return "", common.ErrNotImplementedError
+}
+
 func (p *Process) TgidWithContext(ctx context.Context) (int32, error) {
 	return 0, common.ErrNotImplementedError
 }

process/process_solaris.go

@@ -59,6 +59,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return "", common.ErrNotImplementedError
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	return "", common.ErrNotImplementedError
+}
+
 func (p *Process) TgidWithContext(ctx context.Context) (int32, error) {
 	return 0, common.ErrNotImplementedError
 }

process/process_test.go

@@ -467,6 +467,16 @@ func Test_Process_Exe(t *testing.T) {
 	}
 }
 
+func Test_Process_Cgroup(t *testing.T) {
+	p := testGetProcess()
+
+	_, err := p.Cgroup()
+	skipIfNotImplementedErr(t, err)
+	if err != nil {
+		t.Errorf("getting cgroup error %v", err)
+	}
+}
+
 func Test_Process_CpuPercent(t *testing.T) {
 	p := testGetProcess()
 	_, err := p.Percent(0)
@@ -862,6 +872,13 @@ func BenchmarkProcessName(b *testing.B) {
 	}
 }
 
+func BenchmarkProcessCgroup(b *testing.B) {
+	p := testGetProcess()
+	for i := 0; i < b.N; i++ {
+		p.Cgroup()
+	}
+}
+
 func BenchmarkProcessPpid(b *testing.B) {
 	p := testGetProcess()
 	for i := 0; i < b.N; i++ {

process/process_windows.go

@@ -335,6 +335,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return filepath.Base(exe), nil
 }
 
+func (p *Process) CgroupWithContext(ctx context.Context) (string, error) {
+	return "", common.ErrNotImplementedError
+}
+
 func (p *Process) TgidWithContext(ctx context.Context) (int32, error) {
 	return 0, common.ErrNotImplementedError
 }