Merge pull request #383 from moorereason/feature/pidfile

Add pidfile support

internal/pidfile/README.md

@@ -0,0 +1,4 @@
+Package pidfile is derived from github.com/moby/moby/pkg/pidfile.
+
+Moby is licensed under the Apache License, Version 2.0.
+Copyright 2012-2017 Docker, Inc.

internal/pidfile/mkdirall.go

@@ -0,0 +1,11 @@
+// +build !windows
+
+package pidfile
+
+import "os"
+
+// MkdirAll creates a directory named path along with any necessary parents,
+// with permission specified by attribute perm for all dir created.
+func MkdirAll(path string, perm os.FileMode) error {
+	return os.MkdirAll(path, perm)
+}

internal/pidfile/mkdirall_windows.go

@@ -0,0 +1,109 @@
+// +build windows
+
+package pidfile
+
+import (
+	"os"
+	"regexp"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// MkdirAll implementation that is volume path aware for Windows. It can be used
+// as a drop-in replacement for os.MkdirAll()
+func MkdirAll(path string, _ os.FileMode) error {
+	return mkdirall(path, false, "")
+}
+
+// mkdirall is a custom version of os.MkdirAll modified for use on Windows
+// so that it is both volume path aware, and can create a directory with
+// a DACL.
+func mkdirall(path string, applyACL bool, sddl string) error {
+	if re := regexp.MustCompile(`^\\\\\?\\Volume{[a-z0-9-]+}$`); re.MatchString(path) {
+		return nil
+	}
+
+	// The rest of this method is largely copied from os.MkdirAll and should be kept
+	// as-is to ensure compatibility.
+
+	// Fast path: if we can tell whether path is a directory or file, stop with success or error.
+	dir, err := os.Stat(path)
+	if err == nil {
+		if dir.IsDir() {
+			return nil
+		}
+		return &os.PathError{
+			Op:   "mkdir",
+			Path: path,
+			Err:  syscall.ENOTDIR,
+		}
+	}
+
+	// Slow path: make sure parent exists and then call Mkdir for path.
+	i := len(path)
+	for i > 0 && os.IsPathSeparator(path[i-1]) { // Skip trailing path separator.
+		i--
+	}
+
+	j := i
+	for j > 0 && !os.IsPathSeparator(path[j-1]) { // Scan backward over element.
+		j--
+	}
+
+	if j > 1 {
+		// Create parent
+		err = mkdirall(path[0:j-1], false, sddl)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Parent now exists; invoke os.Mkdir or mkdirWithACL and use its result.
+	if applyACL {
+		err = mkdirWithACL(path, sddl)
+	} else {
+		err = os.Mkdir(path, 0)
+	}
+
+	if err != nil {
+		// Handle arguments like "foo/." by
+		// double-checking that directory doesn't exist.
+		dir, err1 := os.Lstat(path)
+		if err1 == nil && dir.IsDir() {
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+// mkdirWithACL creates a new directory. If there is an error, it will be of
+// type *PathError. .
+//
+// This is a modified and combined version of os.Mkdir and windows.Mkdir
+// in golang to cater for creating a directory am ACL permitting full
+// access, with inheritance, to any subfolder/file for Built-in Administrators
+// and Local System.
+func mkdirWithACL(name string, sddl string) error {
+	sa := windows.SecurityAttributes{Length: 0}
+	sd, err := windows.SecurityDescriptorFromString(sddl)
+	if err != nil {
+		return &os.PathError{Op: "mkdir", Path: name, Err: err}
+	}
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.InheritHandle = 1
+	sa.SecurityDescriptor = sd
+
+	namep, err := windows.UTF16PtrFromString(name)
+	if err != nil {
+		return &os.PathError{Op: "mkdir", Path: name, Err: err}
+	}
+
+	e := windows.CreateDirectory(namep, &sa)
+	if e != nil {
+		return &os.PathError{Op: "mkdir", Path: name, Err: e}
+	}
+	return nil
+}

internal/pidfile/pidfile.go

@@ -0,0 +1,51 @@
+// Package pidfile provides structure and helper functions to create and remove
+// PID file. A PID file is usually a file used to store the process ID of a
+// running process.
+package pidfile
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// PIDFile is a file used to store the process ID of a running process.
+type PIDFile struct {
+	path string
+}
+
+func checkPIDFileAlreadyExists(path string) error {
+	if pidByte, err := ioutil.ReadFile(path); err == nil {
+		pidString := strings.TrimSpace(string(pidByte))
+		if pid, err := strconv.Atoi(pidString); err == nil {
+			if processExists(pid) {
+				return fmt.Errorf("pid file found, ensure webhook is not running or delete %s", path)
+			}
+		}
+	}
+	return nil
+}
+
+// New creates a PIDfile using the specified path.
+func New(path string) (*PIDFile, error) {
+	if err := checkPIDFileAlreadyExists(path); err != nil {
+		return nil, err
+	}
+	// Note MkdirAll returns nil if a directory already exists
+	if err := MkdirAll(filepath.Dir(path), os.FileMode(0755)); err != nil {
+		return nil, err
+	}
+	if err := ioutil.WriteFile(path, []byte(fmt.Sprintf("%d", os.Getpid())), 0644); err != nil {
+		return nil, err
+	}
+
+	return &PIDFile{path: path}, nil
+}
+
+// Remove removes the PIDFile.
+func (file PIDFile) Remove() error {
+	return os.Remove(file.path)
+}

internal/pidfile/pidfile_darwin.go

@@ -0,0 +1,14 @@
+// +build darwin
+
+package pidfile
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+func processExists(pid int) bool {
+	// OS X does not have a proc filesystem.
+	// Use kill -0 pid to judge if the process exists.
+	err := unix.Kill(pid, 0)
+	return err == nil
+}

internal/pidfile/pidfile_test.go

@@ -0,0 +1,38 @@
+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")
+	}
+
+	path := filepath.Join(dir, "testfile")
+	file, err := New(path)
+	if err != nil {
+		t.Fatal("Could not create test file", err)
+	}
+
+	_, err = New(path)
+	if err == nil {
+		t.Fatal("Test file creation not blocked")
+	}
+
+	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")
+	}
+}

internal/pidfile/pidfile_unix.go

@@ -0,0 +1,16 @@
+// +build !windows,!darwin
+
+package pidfile
+
+import (
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+func processExists(pid int) bool {
+	if _, err := os.Stat(filepath.Join("/proc", strconv.Itoa(pid))); err == nil {
+		return true
+	}
+	return false
+}

internal/pidfile/pidfile_windows.go

@@ -0,0 +1,25 @@
+package pidfile
+
+import (
+	"golang.org/x/sys/windows"
+)
+
+const (
+	processQueryLimitedInformation = 0x1000
+
+	stillActive = 259
+)
+
+func processExists(pid int) bool {
+	h, err := windows.OpenProcess(processQueryLimitedInformation, false, uint32(pid))
+	if err != nil {
+		return false
+	}
+	var c uint32
+	err = windows.GetExitCodeProcess(h, &c)
+	windows.Close(h)
+	if err != nil {
+		return c == stillActive
+	}
+	return true
+}