Reconcile active jobs against cancel_attempted_at after notifier reconnects

CHANGELOG.md

@@ -13,6 +13,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Recover `JobCancel()` notifications lost during notifier disconnects by reconciling running jobs after reconnect. [PR #1361](https://github.com/riverqueue/river/pull/1361).
+- Deliver `JobCancel()` locally in `PollOnly` mode without blocking unstarted or stopping clients. [PR #1361](https://github.com/riverqueue/river/pull/1361).
+- Clear previous cancellation metadata when retrying a job. [PR #1361](https://github.com/riverqueue/river/pull/1361).
 - Fixed `AddWorkerSafely` leaving a worker's primary kind and earlier aliases registered when a later kind alias conflicts with an existing registration. Failed registrations now leave the worker registry unchanged. [PR #1440](https://github.com/riverqueue/river/pull/1440).
 - Fixed the notifier retrying without backoff and flooding logs when the context passed to `Client.Start` reaches its deadline. [PR #1495](https://github.com/riverqueue/river/pull/1495).
 

client.go

@@ -1533,11 +1533,13 @@ func (c *Client[TTx]) JobCancel(ctx context.Context, jobID int64) (*rivertype.Jo
 		return nil, err
 	}
 
-	c.notifyProducerWithoutListenerQueueControlEvent(job.Queue, &controlEventPayload{
-		Action: controlActionCancel,
-		JobID:  job.ID,
-		Queue:  job.Queue,
-	})
+	if job.State == rivertype.JobStateRunning {
+		c.notifyProducerOfCancelWithoutNotifier(ctx, job.Queue, &controlEventPayload{
+			Action: controlActionCancel,
+			JobID:  job.ID,
+			Queue:  job.Queue,
+		})
+	}
 
 	return job, nil
 }
@@ -2982,6 +2984,39 @@ func (c *Client[TTx]) notifyProducerWithoutListenerQueueControlEvent(queue strin
 	}
 }
 
+// Deliver cancellations locally when no notifier is configured, including PollOnly.
+// Only call after commit so the producer can observe the cancellation metadata.
+func (c *Client[TTx]) notifyProducerOfCancelWithoutNotifier(ctx context.Context, queue string, controlEvent *controlEventPayload) {
+	if c.notifier != nil {
+		return
+	}
+
+	c.producersMu.RLock()
+	producer := c.producersByQueueName[queue]
+	c.producersMu.RUnlock()
+	if producer == nil {
+		return
+	}
+
+	state := producer.cancelState.Load()
+	if state == nil {
+		return
+	}
+	select {
+	case <-state.done:
+		return
+	default:
+	}
+
+	// cancelCh is also drained while a database fetch is in progress.
+	select {
+	case producer.cancelCh <- controlEvent.JobID:
+		producer.testSignals.QueueControlEventTriggered.Signal(controlEvent)
+	case <-ctx.Done():
+	case <-state.done:
+	}
+}
+
 func (c *Client[TTx]) queueUpdate(ctx context.Context, executorTx riverdriver.ExecutorTx, name string, params *QueueUpdateParams) (*rivertype.Queue, *controlEventPayload, error) {
 	updateMetadata := len(params.Metadata) > 0