Port V2Ray periodic task standard library to snowflake

This is a mature implementation of periodic task that run a function at given interval. It allows task to be stopped, and deals with edge case like interval too short gracefully.

V2Ray/V2Fly is MIT licensed.

common/task/periodic.go

@@ -0,0 +1,85 @@
+package task
+
+import (
+	"sync"
+	"time"
+)
+
+// Periodic is a task that runs periodically.
+type Periodic struct {
+	// Interval of the task being run
+	Interval time.Duration
+	// Execute is the task function
+	Execute func() error
+
+	access  sync.Mutex
+	timer   *time.Timer
+	running bool
+}
+
+func (t *Periodic) hasClosed() bool {
+	t.access.Lock()
+	defer t.access.Unlock()
+
+	return !t.running
+}
+
+func (t *Periodic) checkedExecute() error {
+	if t.hasClosed() {
+		return nil
+	}
+
+	if err := t.Execute(); err != nil {
+		t.access.Lock()
+		t.running = false
+		t.access.Unlock()
+		return err
+	}
+
+	t.access.Lock()
+	defer t.access.Unlock()
+
+	if !t.running {
+		return nil
+	}
+
+	t.timer = time.AfterFunc(t.Interval, func() {
+		t.checkedExecute()
+	})
+
+	return nil
+}
+
+// Start implements common.Runnable.
+func (t *Periodic) Start() error {
+	t.access.Lock()
+	if t.running {
+		t.access.Unlock()
+		return nil
+	}
+	t.running = true
+	t.access.Unlock()
+
+	if err := t.checkedExecute(); err != nil {
+		t.access.Lock()
+		t.running = false
+		t.access.Unlock()
+		return err
+	}
+
+	return nil
+}
+
+// Close implements common.Closable.
+func (t *Periodic) Close() error {
+	t.access.Lock()
+	defer t.access.Unlock()
+
+	t.running = false
+	if t.timer != nil {
+		t.timer.Stop()
+		t.timer = nil
+	}
+
+	return nil
+}