pkg/services: add StopChan & StopRChan from core (#213)

pkg/services/stop.go

@@ -0,0 +1,50 @@
+package services
+
+import "context"
+
+// A StopChan signals when some work should stop.
+// Use StopChanR if you already have a read only <-chan.
+type StopChan chan struct{}
+
+// NewCtx returns a background [context.Context] that is cancelled when StopChan is closed.
+func (s StopChan) NewCtx() (context.Context, context.CancelFunc) {
+	return StopRChan((<-chan struct{})(s)).NewCtx()
+}
+
+// Ctx cancels a [context.Context] when StopChan is closed.
+func (s StopChan) Ctx(ctx context.Context) (context.Context, context.CancelFunc) {
+	return StopRChan((<-chan struct{})(s)).Ctx(ctx)
+}
+
+// CtxCancel cancels a [context.Context] when StopChan is closed.
+// Returns ctx and cancel unmodified, for convenience.
+func (s StopChan) CtxCancel(ctx context.Context, cancel context.CancelFunc) (context.Context, context.CancelFunc) {
+	return StopRChan((<-chan struct{})(s)).CtxCancel(ctx, cancel)
+}
+
+// A StopRChan signals when some work should stop.
+// This is a receive-only version of StopChan, for casting an existing <-chan.
+type StopRChan <-chan struct{}
+
+// NewCtx returns a background [context.Context] that is cancelled when StopChan is closed.
+func (s StopRChan) NewCtx() (context.Context, context.CancelFunc) {
+	return s.Ctx(context.Background())
+}
+
+// Ctx cancels a [context.Context] when StopChan is closed.
+func (s StopRChan) Ctx(ctx context.Context) (context.Context, context.CancelFunc) {
+	return s.CtxCancel(context.WithCancel(ctx))
+}
+
+// CtxCancel cancels a [context.Context] when StopChan is closed.
+// Returns ctx and cancel unmodified, for convenience.
+func (s StopRChan) CtxCancel(ctx context.Context, cancel context.CancelFunc) (context.Context, context.CancelFunc) {
+	go func() {
+		select {
+		case <-s:
+			cancel()
+		case <-ctx.Done():
+		}
+	}()
+	return ctx, cancel
+}

pkg/utils/utils.go

@@ -5,6 +5,8 @@ import (
 	"math"
 	mrand "math/rand"
 	"time"
+
+	"github.com/smartcontractkit/chainlink-relay/pkg/services"
 )
 
 // WithJitter adds +/- 10% to a duration
@@ -27,15 +29,7 @@ func WithJitter(d time.Duration) time.Duration {
 // NOTE: Spins up a goroutine that exits on cancellation.
 // REMEMBER TO CALL CANCEL OTHERWISE IT CAN LEAD TO MEMORY LEAKS
 func ContextFromChan(chStop <-chan struct{}) (context.Context, context.CancelFunc) {
-	ctx, cancel := context.WithCancel(context.Background())
-	go func() {
-		select {
-		case <-chStop:
-			cancel()
-		case <-ctx.Done():
-		}
-	}()
-	return ctx, cancel
+	return services.StopRChan(chStop).NewCtx()
 }
 
 // ContextWithDeadlineFn returns a copy of the parent context with the deadline modified by deadlineFn.