Moved pidfile from utils to pkg

Fixes #10958 by moving utils.daemon to pkg.pidfile.
Test cases were also added.
Updated the daemon to use the new pidfile.

Signed-off-by: Rick Wieman <git@rickw.nl>

pidfile/pidfile.go

@@ -0,0 +1,44 @@
+package pidfile
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+type PidFile struct {
+	path string
+}
+
+func checkPidFileAlreadyExists(path string) error {
+	if pidString, err := ioutil.ReadFile(path); err == nil {
+		if pid, err := strconv.Atoi(string(pidString)); err == nil {
+			if _, err := os.Stat(filepath.Join("/proc", string(pid))); err == nil {
+				return fmt.Errorf("pid file found, ensure docker is not running or delete %s", path)
+			}
+		}
+	}
+	return nil
+}
+
+func New(path string) (file *PidFile, err error) {
+	if err := checkPidFileAlreadyExists(path); err != nil {
+		return nil, err
+	}
+
+	file = &PidFile{path: path}
+	err = ioutil.WriteFile(path, []byte(fmt.Sprintf("%d", os.Getpid())), 0644)
+
+	return file, err
+}
+
+func (file PidFile) Remove() error {
+	if err := os.Remove(file.path); err != nil {
+		log.Printf("Error removing %s: %s", file.path, err)
+		return err
+	}
+	return nil
+}

pidfile/pidfile_test.go

@@ -0,0 +1,32 @@
+package pidfile
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestNewAndRemove(t *testing.T) {
+	dir, err := ioutil.TempDir(os.TempDir(), "test-pidfile")
+	if err != nil {
+		t.Fatal("Could not create test directory")
+	}
+
+	file, err := New(filepath.Join(dir, "testfile"))
+	if err != nil {
+		t.Fatal("Could not create test file", err)
+	}
+
+	if err := file.Remove(); err != nil {
+		t.Fatal("Could not delete created test file")
+	}
+}
+
+func TestRemoveInvalidPath(t *testing.T) {
+	file := PidFile{path: filepath.Join("foo", "bar")}
+
+	if err := file.Remove(); err == nil {
+		t.Fatal("Non-existing file doesn't give an error on delete")
+	}
+}