fix(grpc/client,node/task/handler): add RetryWithBackoff, stabilize reconnection, and retry gRPC ops

- add RetryWithBackoff helper to grpc client for exponential retry with backoff and reconnection-aware handling
- increase reconnectionClientTimeout to 90s and introduce connectionStabilizationDelay; wait briefly after reconnection to avoid immediate flapping
- refresh reconnection flag while waiting for client registration and improve cancellation message
- replace direct heartbeat RPC with RetryWithBackoff in WorkerService (use extended timeout)
- use RetryWithBackoff for worker node status updates in task handler and propagate errors

core/grpc/client/client.go

@@ -20,16 +20,17 @@ import (
 
 // Circuit breaker constants
 const (
-	maxFailures               = 5
-	cbResetTime               = 2 * time.Minute
-	cbHalfOpenRetryInterval   = 30 * time.Second
-	healthCheckInterval       = 2 * time.Minute // Reduced frequency from 30 seconds
-	stateMonitorInterval      = 5 * time.Second
-	registrationCheckInterval = 100 * time.Millisecond
-	idleGracePeriod           = 2 * time.Minute // Increased from 30 seconds
-	connectionTimeout         = 30 * time.Second
-	defaultClientTimeout      = 15 * time.Second // Increased from 5s for better reconnection handling
-	reconnectionClientTimeout = 60 * time.Second // Extended timeout during reconnection scenarios
+	maxFailures                  = 5
+	cbResetTime                  = 2 * time.Minute
+	cbHalfOpenRetryInterval      = 30 * time.Second
+	healthCheckInterval          = 2 * time.Minute // Reduced frequency from 30 seconds
+	stateMonitorInterval         = 5 * time.Second
+	registrationCheckInterval    = 100 * time.Millisecond
+	idleGracePeriod              = 2 * time.Minute // Increased from 30 seconds
+	connectionTimeout            = 30 * time.Second
+	defaultClientTimeout         = 15 * time.Second // Increased from 5s for better reconnection handling
+	reconnectionClientTimeout    = 90 * time.Second // Extended timeout during reconnection scenarios (must be > worker reset timeout)
+	connectionStabilizationDelay = 2 * time.Second  // Wait after reconnection before declaring success
 )
 
 // Circuit breaker states
@@ -49,6 +50,54 @@ func min(a, b int) int {
 	return b
 }
 
+// RetryWithBackoff retries an operation up to maxAttempts times with exponential backoff.
+// It detects "reconnection in progress" errors and retries appropriately.
+// Returns the last error if all attempts fail, or nil on success.
+func RetryWithBackoff(ctx context.Context, operation func() error, maxAttempts int, logger interfaces.Logger, operationName string) error {
+	var lastErr error
+	for attempt := 0; attempt < maxAttempts; attempt++ {
+		if attempt > 0 {
+			// Exponential backoff: 1s, 2s, 4s, ...
+			backoffDelay := time.Duration(1<<uint(attempt-1)) * time.Second
+			if logger != nil {
+				logger.Debugf("retrying %s after %v (attempt %d/%d)", operationName, backoffDelay, attempt+1, maxAttempts)
+			}
+
+			select {
+			case <-ctx.Done():
+				if logger != nil {
+					logger.Debugf("%s retry cancelled due to context", operationName)
+				}
+				return ctx.Err()
+			case <-time.After(backoffDelay):
+			}
+		}
+
+		err := operation()
+		if err == nil {
+			if attempt > 0 && logger != nil {
+				logger.Infof("%s succeeded after %d attempts", operationName, attempt+1)
+			}
+			return nil
+		}
+
+		lastErr = err
+		// Check if error indicates reconnection in progress
+		if strings.Contains(err.Error(), "reconnection in progress") {
+			if logger != nil {
+				logger.Debugf("%s waiting for reconnection (attempt %d/%d): %v", operationName, attempt+1, maxAttempts, err)
+			}
+			continue
+		}
+
+		if logger != nil {
+			logger.Debugf("%s failed (attempt %d/%d): %v", operationName, attempt+1, maxAttempts, err)
+		}
+	}
+
+	return fmt.Errorf("%s failed after %d attempts: %v", operationName, maxAttempts, lastErr)
+}
+
 // GrpcClient provides a robust gRPC client with connection management and client registration.
 //
 // The client handles connection lifecycle and ensures that gRPC service clients are properly
@@ -695,12 +744,17 @@ func (c *GrpcClient) getClientWithContext(ctx context.Context, getter func() int
 		select {
 		case <-ctx.Done():
 			if isReconnecting {
-				return nil, fmt.Errorf("context cancelled while waiting for %s client registration during reconnection (this is normal during network restoration)", clientType)
+				return nil, fmt.Errorf("context cancelled while waiting for %s client registration: reconnection in progress, retry recommended", clientType)
 			}
 			return nil, fmt.Errorf("context cancelled while waiting for %s client registration", clientType)
 		case <-c.stop:
 			return nil, fmt.Errorf("client stopped while waiting for %s client registration", clientType)
 		case <-ticker.C:
+			// Update reconnection status in case it changed
+			c.reconnectMux.Lock()
+			isReconnecting = c.reconnecting
+			c.reconnectMux.Unlock()
+
 			if c.IsRegistered() {
 				return getter(), nil
 			}
@@ -771,6 +825,18 @@ func (c *GrpcClient) executeReconnection() {
 	} else {
 		c.recordSuccess()
 		c.Infof("reconnection successful - connection state: %s, registered: %v", c.getState(), c.IsRegistered())
+
+		// Stabilization: wait a moment to ensure connection is truly stable
+		// This prevents immediate flapping if the network is still unstable
+		c.Debugf("stabilizing connection for %v", connectionStabilizationDelay)
+		time.Sleep(connectionStabilizationDelay)
+
+		// Verify connection is still stable after delay
+		if c.conn != nil && c.conn.GetState() == connectivity.Ready {
+			c.Infof("connection stabilization successful")
+		} else {
+			c.Warnf("connection became unstable during stabilization")
+		}
 	}
 }
 

core/node/service/worker_service.go

@@ -338,18 +338,25 @@ func (svc *WorkerService) subscribe() {
 }
 
 func (svc *WorkerService) sendHeartbeat() {
-	ctx, cancel := context.WithTimeout(svc.ctx, svc.heartbeatInterval)
+	// Use extended timeout to allow for reconnection scenarios
+	ctx, cancel := context.WithTimeout(svc.ctx, 30*time.Second)
 	defer cancel()
-	nodeClient, err := client.GetGrpcClient().GetNodeClient()
+
+	// Retry up to 3 times with exponential backoff for reconnection scenarios
+	err := client.RetryWithBackoff(ctx, func() error {
+		nodeClient, err := client.GetGrpcClient().GetNodeClient()
+		if err != nil {
+			return err
+		}
+
+		_, err = nodeClient.SendHeartbeat(ctx, &grpc.NodeServiceSendHeartbeatRequest{
+			NodeKey: svc.cfgSvc.GetNodeKey(),
+		})
+		return err
+	}, 3, svc.Logger, "heartbeat")
+
 	if err != nil {
-		svc.Errorf("failed to get node client: %v", err)
-		return
-	}
-	_, err = nodeClient.SendHeartbeat(ctx, &grpc.NodeServiceSendHeartbeatRequest{
-		NodeKey: svc.cfgSvc.GetNodeKey(),
-	})
-	if err != nil {
-		svc.Errorf("failed to send heartbeat to master: %v", err)
+		svc.Errorf("failed to send heartbeat: %v", err)
 	}
 }
 

core/task/handler/service.go

@@ -438,15 +438,25 @@ func (svc *Service) updateNodeStatus() (err error) {
 	currentGoroutines := runtime.NumGoroutine()
 	svc.Debugf("Node status update - runners: %d, goroutines: %d", n.CurrentRunners, currentGoroutines)
 
-	// save node
+	// save node with retry for reconnection scenarios
 	n.SetUpdated(n.CreatedBy)
 	if svc.cfgSvc.IsMaster() {
 		err = service.NewModelService[models.Node]().ReplaceById(n.Id, *n)
+		if err != nil {
+			return err
+		}
 	} else {
-		err = client.NewModelService[models.Node]().ReplaceById(n.Id, *n)
-	}
-	if err != nil {
-		return err
+		// Worker node: use gRPC with retry logic
+		ctx, cancel := context.WithTimeout(svc.ctx, 30*time.Second)
+		defer cancel()
+
+		err = grpcclient.RetryWithBackoff(ctx, func() error {
+			return client.NewModelService[models.Node]().ReplaceById(n.Id, *n)
+		}, 3, svc.Logger, "node status update")
+
+		if err != nil {
+			return err
+		}
 	}
 
 	return nil