Fix the inability to start with logger in docker contianer (#178)

* check for docker/lxc in isInteractive() for linux

* more clear logic and function name

* add some tests for linux part

* fix test

* cover coverage

service_linux.go

@@ -5,10 +5,13 @@
 package service
 
 import (
+	"bufio"
 	"os"
 	"strings"
 )
 
+var cgroupFile = "/proc/1/cgroup"
+
 type linuxSystemService struct {
 	name        string
 	detect      func() bool
@@ -62,7 +65,37 @@ func init() {
 
 func isInteractive() (bool, error) {
 	// TODO: This is not true for user services.
-	return os.Getppid() != 1, nil
+	inContainer, err := isInContainer(cgroupFile)
+	if err != nil {
+		return false, err
+	}
+	return os.Getppid() != 1 || inContainer, nil
+}
+
+// isInContainer checks if the service is being executed in docker or lxc
+// container.
+func isInContainer(cgroupPath string) (bool, error) {
+	const maxlines = 5 // maximum lines to scan
+
+	f, err := os.Open(cgroupPath)
+	if err != nil {
+		return false, err
+	}
+	defer f.Close()
+	scan := bufio.NewScanner(f)
+
+	lines := 0
+	for scan.Scan() && !(lines > maxlines) {
+		if strings.Contains(scan.Text(), "docker") || strings.Contains(scan.Text(), "lxc") {
+			return true, nil
+		}
+		lines++
+	}
+	if err := scan.Err(); err != nil {
+		return false, err
+	}
+
+	return false, nil
 }
 
 var tf = map[string]interface{}{

service_linux_test.go

@@ -0,0 +1,173 @@
+// Copyright 2015 Daniel Theophanes.
+// Use of this source code is governed by a zlib-style
+// license that can be found in the LICENSE file.
+
+package service
+
+import (
+	"errors"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+// createTestCgroupFiles creates mock files for tests
+func createTestCgroupFiles() (*os.File, *os.File, error) {
+	// docker cgroup setup
+	hDockerGrp, err := ioutil.TempFile("", "*")
+	if err != nil {
+		return nil, nil, errors.New("docker tempfile create failed")
+	}
+	_, err = hDockerGrp.Write([]byte(dockerCgroup))
+	if err != nil {
+		return nil, nil, errors.New("docker tempfile write failed")
+	}
+
+	// linux cgroup setup
+	hLinuxGrp, err := ioutil.TempFile("", "*")
+	if err != nil {
+		return nil, nil, errors.New("\"normal\" tempfile  create failed")
+	}
+	_, err = hLinuxGrp.Write([]byte(linuxCgroup))
+	if err != nil {
+		return nil, nil, errors.New("\"normal\" tempfile write failed")
+	}
+
+	return hDockerGrp, hLinuxGrp, nil
+}
+
+// removeTestFile closes and removes the provided file
+func removeTestFile(hFile *os.File) {
+	hFile.Close()
+	os.Remove(hFile.Name())
+}
+
+func Test_isInContainer(t *testing.T) {
+
+	// setup
+	hDockerGrp, hLinuxGrp, err := createTestCgroupFiles()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		// tear down
+		removeTestFile(hDockerGrp)
+		removeTestFile(hLinuxGrp)
+	}()
+
+	// TEST
+	type args struct {
+		cgroupPath string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    bool
+		wantErr bool
+	}{
+		{"docker", args{hDockerGrp.Name()}, true, false},
+		{"linux", args{hLinuxGrp.Name()}, false, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := isInContainer(tt.args.cgroupPath)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("isInContainer() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("isInContainer() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_isInteractive(t *testing.T) {
+
+	// setup
+	hDockerGrp, hLinuxGrp, err := createTestCgroupFiles()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		// tear down
+		removeTestFile(hDockerGrp)
+		removeTestFile(hLinuxGrp)
+	}()
+
+	// stack emulation for before() and after() for storing global values
+	strStack := make(chan string, 4)
+
+	// TEST
+	tests := []struct {
+		name    string
+		before  func()
+		after   func()
+		want    bool
+		wantErr bool
+	}{
+		{"docker",
+			func() {
+				strStack <- cgroupFile
+				cgroupFile = hDockerGrp.Name()
+			},
+			func() {
+				cgroupFile = <-strStack
+			},
+			true, false,
+		},
+		{"linux",
+			func() {
+				strStack <- cgroupFile
+				cgroupFile = hLinuxGrp.Name()
+			},
+			func() {
+				cgroupFile = <-strStack
+			},
+			true, false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.before()
+			got, err := isInteractive()
+			tt.after()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("isInteractive() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("isInteractive() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+const (
+	dockerCgroup = `13:name=systemd:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+12:pids:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+11:hugetlb:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+10:net_prio:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+9:perf_event:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+8:net_cls:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+7:freezer:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+6:devices:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+5:memory:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+4:blkio:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+3:cpuacct:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+2:cpu:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee
+1:cpuset:/docker/bc9f0894926991e3064b731c26d86af6df7390c0e6453e6027f9545aba5809ee`
+
+	linuxCgroup = `11:cpuset:/
+10:pids:/init.scope
+9:perf_event:/
+8:memory:/init.scope
+7:blkio:/
+6:devices:/init.scope
+5:rdma:/
+4:net_cls,net_prio:/
+3:freezer:/
+2:cpu,cpuacct:/
+1:name=systemd:/init.scope
+0::/init.scope`
+)