Add config file monitoring feature

configor.go

@@ -3,9 +3,13 @@ package configor
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"reflect"
 	"regexp"
+	"sync"
 	"time"
+
+	"github.com/fsnotify/fsnotify"
 )
 
 type Configor struct {
@@ -27,6 +31,8 @@ type Config struct {
 	// go 1.10 or later.
 	// This field will be ignored when compiled with go versions lower than 1.10.
 	ErrorOnUnmatchedKeys bool
+
+	OnConfigChange func(e fsnotify.Event)
 }
 
 // New initialize a Configor
@@ -119,3 +125,68 @@ func ENV() string {
 func Load(config interface{}, files ...string) error {
 	return New(nil).Load(config, files...)
 }
+
+func Watch(config interface{}, files ...string) {
+	New(nil).Watch(config, files...)
+}
+
+func (configor *Configor) Watch(config interface{}, files ...string) {
+	initWG := sync.WaitGroup{}
+	initWG.Add(1)
+	for _, file := range files {
+
+		go func() {
+			watcher, err := newWatcher()
+			if err != nil {
+				fmt.Printf("Failed to create watcher for %v, got error %v\n", file, err)
+			}
+			defer watcher.Close()
+
+			configFile := filepath.Clean(file)
+			configDir, _ := filepath.Split(configFile)
+			realConfigFile, _ := filepath.EvalSymlinks(file)
+
+			eventsWG := sync.WaitGroup{}
+			eventsWG.Add(1)
+			go func() {
+				for {
+					select {
+					case event, ok := <-watcher.Events:
+						if !ok {
+							eventsWG.Done()
+							return
+						}
+
+						currentConfigFile, _ := filepath.EvalSymlinks(file)
+						const writeOrCreateMask = fsnotify.Write | fsnotify.Create
+						if (event.Op&writeOrCreateMask != 0 && currentConfigFile == event.Name) ||
+							(currentConfigFile != "" && currentConfigFile != realConfigFile) {
+							err := configor.Load(config, files...)
+							if err != nil {
+								fmt.Printf("Failed to reload configuration from %v, got error %v\n", files, err)
+							}
+							if configor.Config.OnConfigChange != nil {
+								configor.Config.OnConfigChange(event)
+							}
+						} else if filepath.Clean(event.Name) == configFile &&
+							event.Op&fsnotify.Remove&fsnotify.Remove != 0 {
+							eventsWG.Done()
+							return
+						}
+
+					case err, ok := <-watcher.Errors:
+						if ok {
+							fmt.Printf("Failed to watch configuration from %v, got error %v\n", files, err)
+						}
+						eventsWG.Done()
+						return
+					}
+				}
+			}()
+			watcher.Add(configDir)
+			initWG.Done()
+			eventsWG.Wait()
+		}()
+		initWG.Wait()
+	}
+}

configor_test.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/BurntSushi/toml"
 	"gopkg.in/yaml.v2"
@@ -681,3 +682,40 @@ func TestLoadNestedConfig(t *testing.T) {
 	adminConfig := MenuList{}
 	New(&Config{Verbose: true}).Load(&adminConfig, "admin.yml")
 }
+
+func TestWatchNormalConfig(t *testing.T) {
+	var result testConfig
+	config := generateDefaultConfig()
+	if bytes, err := json.Marshal(config); err == nil {
+		if file, err := ioutil.TempFile("/tmp", "configor"); err == nil {
+			defer file.Close()
+			defer os.Remove(file.Name())
+			file.Write(bytes)
+
+			//Load(&result, file.Name())
+			Watch(&result, file.Name())
+
+			time.Sleep(time.Second)
+			if !reflect.DeepEqual(result, config) {
+				t.Errorf("result should equal to original configuration")
+			}
+
+			config.Hosts = []string{
+				"whocallthefleet.org",
+				"abandonship.org",
+			}
+			if bytes, err = json.Marshal(config); err != nil {
+				t.Errorf("Failed to marshal config")
+			}
+			file.Seek(0, 0)
+			file.Write(bytes)
+
+			time.Sleep(1 * time.Second)
+			if !reflect.DeepEqual(result, config) {
+				t.Errorf("watch test failed: result should equal to original configuration")
+			}
+		} else {
+			t.Errorf("Failed to marshal config")
+		}
+	}
+}

go.mod

@@ -4,5 +4,6 @@ go 1.12
 
 require (
 	github.com/BurntSushi/toml v0.3.1
+	github.com/fsnotify/fsnotify v1.5.1
 	gopkg.in/yaml.v2 v2.2.2
 )

go.sum

@@ -1,5 +1,9 @@
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/fsnotify/fsnotify v1.5.1 h1:mZcQUHVQUQWoPXXtuf9yuEXKudkV2sx1E06UadKWpgI=
+github.com/fsnotify/fsnotify v1.5.1/go.mod h1:T3375wBYaZdLLcVNkcVbzGHY7f1l/uK5T5Ai1i3InKU=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c h1:F1jZWGFhYfh0Ci55sIpILtKKK8p3i2/krTr0H1rg74I=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=

watch.go

@@ -0,0 +1,9 @@
+package configor
+
+import "github.com/fsnotify/fsnotify"
+
+type watcher = fsnotify.Watcher
+
+func newWatcher() (*watcher, error) {
+	return fsnotify.NewWatcher()
+}