Add Backoff interface (#12)

* feat: Add Backoff interface to support customizable backoff policies (#8)

* refactor: Update worker and manager to use Backoff interface (#8)

Author: KengoWada

backoff.go

@@ -5,6 +5,22 @@ import (
 	"time"
 )
 
+var DefaultBackoffPolicy = BackoffPolicy{
+	BaseDelay:     1 * time.Second,
+	MaxDelay:      30 * time.Second,
+	UseJitter:     true,
+	JitterRangeMs: 300,
+}
+
+// Backoff defines the interface for calculating backoff delays between retries.
+// Implementations of this interface can provide custom logic for determining
+// how long to wait before retrying a failed task based on the number of retries.
+type Backoff interface {
+	// Calculate returns the duration to wait before the next retry attempt.
+	// The input parameter retries indicates how many times the task has already been retried.
+	Calculate(retries int) time.Duration
+}
+
 // BackoffPolicy defines the configuration for handling retries with backoff logic.
 // It provides settings for base delay, maximum delay, jitter, and the range for jitter.
 type BackoffPolicy struct {

manager.go

@@ -17,7 +17,7 @@ type ManagerOption func(*ManagerConfig)
 
 // ManagerConfig holds configuration options for the Manager.
 type ManagerConfig struct {
-	BackoffPolicy *BackoffPolicy
+	BackoffPolicy Backoff
 }
 
 // Manager is responsible for managing the lifecycle of workers,
@@ -37,7 +37,7 @@ type Manager struct {
 // Example usage:
 //
 //	manager := NewManager(bp, numOfWorkers, WithBackoffPolicy(customBackoffPolicy))
-func WithBackoffPolicy(bp *BackoffPolicy) ManagerOption {
+func WithBackoffPolicy(bp Backoff) ManagerOption {
 	return func(cfg *ManagerConfig) {
 		cfg.BackoffPolicy = bp
 	}
@@ -79,14 +79,8 @@ func NewManager(broker Broker, wf WorkerFactory, numWorkers int, opts ...Manager
 		opt(managerConfig)
 	}
 
-	// Set default backoff if cfg.BackoffPolicy == nil
 	if managerConfig.BackoffPolicy == nil {
-		managerConfig.BackoffPolicy = &BackoffPolicy{
-			BaseDelay:     1 * time.Second,
-			MaxDelay:      30 * time.Second,
-			UseJitter:     true,
-			JitterRangeMs: 300,
-		}
+		managerConfig.BackoffPolicy = &DefaultBackoffPolicy
 	}
 
 	manager := &Manager{broker: broker, ctx: ctx, cancel: cancel}

worker.go

@@ -65,7 +65,7 @@ type WorkerFactory func(cfg WorkerConfig) Worker
 type WorkerConfig struct {
 	ID      int
 	Broker  Broker
-	Backoff *BackoffPolicy
+	Backoff Backoff
 	WG      *sync.WaitGroup
 }
 
@@ -86,7 +86,7 @@ type WorkerConfig struct {
 type DefaultWorker struct {
 	id       int
 	broker   Broker
-	backoff  *BackoffPolicy
+	backoff  Backoff
 	handlers map[string]TaskHandlerFunc
 	wg       *sync.WaitGroup
 }