Merge pull request #31 from donutloop/feat/lease

Leaser: Lease the resource for duration. When the lease expires, invo…

Author: donutloop

debugutil/README.md

@@ -1,6 +1,6 @@
 # Usage
 
-PrettyPrint generates a human readable representation of the value v.
+PrettySprint generates a human readable representation of the value v.
 
 ## Example 
 ```go 
@@ -12,6 +12,6 @@ import (
 )
 
 func main() {
-    debugutil.PrettyPrint([]string{})
+    log.Println(debugutil.PrettySprint([]string{})
 }
 ```

lease/README.md

@@ -0,0 +1,19 @@
+# Usage
+
+lease the resource for duration. When the lease expires, invoke func
+
+## Example
+```go 
+package main 
+
+import (
+	"github.com/donutloop/toolkit/lease"
+)
+
+func main() {
+    leaser := lease.NewLeaser()
+    leaser.Lease("cleanup-cache", time.Duration(1*time.Second), func() {
+    	fmt.Println("cleaned up cache")
+    })
+}
+```

lease/doc_test.go

@@ -0,0 +1,20 @@
+package lease_test
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/donutloop/toolkit/lease"
+)
+
+func ExampleLeaser_Lease() {
+
+	leaser := lease.NewLeaser()
+	leaser.Lease("cleanup-cache", time.Duration(1*time.Second), func() {
+		fmt.Println("cleaned up cache")
+	})
+
+	<-time.After(2 * time.Second)
+
+	// Output: cleaned up cache
+}

lease/lease.go

@@ -0,0 +1,40 @@
+package lease
+
+import "time"
+
+type Leaser interface {
+	// lease the resource r for duration. When the lease expires, invoke func call.
+	// revoke a lease can be refreshed by calling Lease() again on the same resource
+	Lease(r string, d time.Duration, revoke func())
+	// if resource exists then cancel the old timer and delete the entry
+	Return(r string) bool
+}
+
+// NewLeaser creates a instance of leaser
+func NewLeaser() Leaser {
+	return &leaser{
+		timers: make(map[string]*time.Timer),
+	}
+}
+
+type leaser struct {
+	timers map[string]*time.Timer
+}
+
+func (l *leaser) Lease(r string, d time.Duration, f func()) {
+	timer := time.AfterFunc(d, f)
+	// if resource exists then cancel the old timer and overwrite the old one
+	if t, ok := l.timers[r]; ok {
+		t.Stop()
+	}
+	l.timers[r] = timer
+}
+
+// if resource exists then cancel the old timer and delete the entry
+func (l *leaser) Return(r string) bool {
+	if t, ok := l.timers[r]; ok {
+		t.Stop()
+		return true
+	}
+	return false
+}

lease/lease_test.go

@@ -0,0 +1,61 @@
+package lease_test
+
+import (
+	"testing"
+	"time"
+
+	"sync/atomic"
+
+	"github.com/donutloop/toolkit/lease"
+)
+
+func TestLeaser_Lease(t *testing.T) {
+	var counter int32
+	leaser := lease.NewLeaser()
+	leaser.Lease("cleanup-cache", time.Duration(1*time.Second), func() {
+		atomic.AddInt32(&counter, 1)
+	})
+
+	<-time.After(2 * time.Second)
+
+	if counter != 1 {
+		t.Errorf(`unexpected counter value (actual:"%d", expected: "%d")`, counter, 1)
+	}
+}
+
+func TestLeaser_OverwriteLease(t *testing.T) {
+	var counter int32
+	leaser := lease.NewLeaser()
+	leaser.Lease("cleanup-cache", time.Duration(2*time.Second), func() {
+		atomic.AddInt32(&counter, 1)
+	})
+
+	leaser.Lease("cleanup-cache", time.Duration(1*time.Second), func() {
+		atomic.AddInt32(&counter, 2)
+	})
+
+	<-time.After(3 * time.Second)
+
+	if counter != 2 {
+		t.Errorf(`unexpected counter value (actual:"%d", expected: "%d")`, counter, 2)
+	}
+}
+
+func TestLeaser_Return(t *testing.T) {
+	var counter int32
+	leaser := lease.NewLeaser()
+	leaser.Lease("cleanup-cache", time.Duration(1*time.Second), func() {
+		atomic.AddInt32(&counter, 1)
+	})
+
+	ok := leaser.Return("cleanup-cache")
+	if !ok {
+		t.Error("error couldn't return resource")
+	}
+
+	<-time.After(2 * time.Second)
+
+	if counter != 0 {
+		t.Errorf(`unexpected counter value (actual:"%d", expected: "%d")`, counter, 0)
+	}
+}