Remove cgo and use 'getent passwd' to lookup user names

.promu.yml

@@ -1,6 +1,6 @@
 go:
   version: 1.20
-  cgo: true
+  cgo: false
 repository:
     path: github.com/treydock/cgroup_exporter
 build:

collector/cgroupv1.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"fmt"
-	"os/user"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -45,11 +44,11 @@ func getInfov1(name string, metric *CgroupMetric, logger log.Logger) {
 	if len(userSliceMatch) == 2 {
 		metric.userslice = true
 		metric.uid = userSliceMatch[1]
-		user, err := user.LookupId(metric.uid)
+		user, err := getentPasswd(metric.uid)
 		if err != nil {
 			level.Error(logger).Log("msg", "Error looking up user slice uid", "uid", metric.uid, "err", err)
 		} else {
-			metric.username = user.Username
+			metric.username = user
 		}
 		return
 	}
@@ -59,11 +58,11 @@ func getInfov1(name string, metric *CgroupMetric, logger log.Logger) {
 		metric.job = true
 		metric.uid = slurmMatch[1]
 		metric.jobid = slurmMatch[2]
-		user, err := user.LookupId(metric.uid)
+		user, err := getentPasswd(metric.uid)
 		if err != nil {
 			level.Error(logger).Log("msg", "Error looking up slurm uid", "uid", metric.uid, "err", err)
 		} else {
-			metric.username = user.Username
+			metric.username = user
 		}
 		return
 	}

collector/cgroupv2.go

@@ -88,12 +88,12 @@ func getInfov2(name string, pids []int, metric *CgroupMetric, logger log.Logger)
 		// effective UID
 		uid := procStat.UIDs[1]
 		metric.uid = uid
-		user, err := user.LookupId(metric.uid)
+		user, err := getentPasswd(metric.uid)
 		if err != nil {
 			level.Error(logger).Log("msg", "Error looking up slurm uid", "uid", metric.uid, "err", err)
 			return
 		}
-		metric.username = user.Username
+		metric.username = user
 		return
 	}
 }

collector/collector.go

@@ -14,8 +14,11 @@
 package collector
 
 import (
+	"bytes"
+	"context"
 	"fmt"
 	"os"
+	"os/exec"
 	"reflect"
 	"strconv"
 	"strings"
@@ -33,7 +36,9 @@ var (
 	CgroupRoot         = kingpin.Flag("path.cgroup.root", "Root path to cgroup fs").Default(defCgroupRoot).String()
 	collectProcMaxExec = kingpin.Flag("collect.proc.max-exec", "Max length of process executable to record").Default("100").Int()
 	ProcRoot           = kingpin.Flag("path.proc.root", "Root path to proc fs").Default(defProcRoot).String()
+	userLookupTimeout  = kingpin.Flag("exec.getent.timeout", "Timeout for running 'getent passwd' command").Default("5s").Duration()
 	metricLock         = sync.RWMutex{}
+	execCommand        = exec.CommandContext
 )
 
 const (
@@ -311,3 +316,20 @@ func sliceContains(s interface{}, v interface{}) bool {
 	}
 	return false
 }
+
+func getentPasswd(uid string) (string, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), *userLookupTimeout)
+	defer cancel()
+	cmd := execCommand(ctx, "getent", "passwd", uid)
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	err := cmd.Run()
+	if ctx.Err() == context.DeadlineExceeded {
+		return "", fmt.Errorf("Timeout executing: getent passwd %s", uid)
+	} else if err != nil {
+		return "", fmt.Errorf("Error executing 'getent passwd %s': %s %s", uid, stderr.String(), err.Error())
+	}
+	username := strings.Split(stdout.String(), ":")[0]
+	return username, nil
+}

collector/collector_test.go

@@ -14,15 +14,25 @@
 package collector
 
 import (
+	"context"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"reflect"
 	"runtime"
+	"strconv"
 	"testing"
+	"time"
 
 	"github.com/go-kit/log"
 )
 
+var (
+	mockedExitStatus = 0
+	mockedStdout     string
+	_, cancel        = context.WithTimeout(context.Background(), 5*time.Second)
+)
+
 func TestMain(m *testing.M) {
 	_, filename, _, _ := runtime.Caller(0)
 	dir := filepath.Dir(filename)
@@ -84,3 +94,33 @@ func TestGetProcInfo(t *testing.T) {
 		}
 	}
 }
+
+func fakeExecCommand(ctx context.Context, command string, args ...string) *exec.Cmd {
+	cs := []string{"-test.run=TestExecCommandHelper", "--", command}
+	cs = append(cs, args...)
+	defer cancel()
+	cmd := exec.CommandContext(ctx, os.Args[0], cs...)
+	es := strconv.Itoa(mockedExitStatus)
+	tmp, _ := os.MkdirTemp("", "fake")
+	cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1",
+		"GOCOVERDIR=" + tmp,
+		"STDOUT=" + mockedStdout,
+		"EXIT_STATUS=" + es}
+	return cmd
+}
+
+func TestGetentPasswd(t *testing.T) {
+	timeout := 5 * time.Second
+	userLookupTimeout = &timeout
+	execCommand = fakeExecCommand
+	mockedExitStatus = 0
+	mockedStdout = "adm:x:3:4:adm:/var/adm:/sbin/nologin"
+	defer func() { execCommand = exec.CommandContext }()
+	user, err := getentPasswd("3")
+	if err != nil {
+		t.Errorf("Unexpected error: %s", err.Error())
+	}
+	if user != "adm" {
+		t.Errorf("Unexpected user: %s", user)
+	}
+}