Re-read a delivery before failing it for a missing target

failMissingTarget failed the delivery as the batch had read it, so a
delivery a worker sent and let go between the batch read and the
ownership check could end failed after a successful attempt. It now
reads the row once it owns the delivery and fails it only if the
status is still the one the batch read, as processNewTask does. A row
that cannot be read is left alone.

TestSweepPending_TargetDeleted now checks that the first sweep already
queues the healthy delivery and the second does not queue it again.

Model: opus-5-5

internal/delivery/engine.go

@@ -728,9 +728,7 @@ func (e *Engine) recoverSingleRetry(
 		// webhook on one bad read would be a far larger fault than
 		// the strand it is meant to clear.
 		if errors.Is(err, gorm.ErrRecordNotFound) {
-			e.failMissingTargetRetry(
-				webhookDB, webhookID, d,
-			)
+			e.failMissingTarget(webhookDB, webhookID, d)
 
 			return
 		}
@@ -1133,9 +1131,7 @@ func (e *Engine) sweepSingleRetry(
 		// Deleted is terminal, unreadable is not; see
 		// recoverSingleRetry.
 		if errors.Is(err, gorm.ErrRecordNotFound) {
-			e.failMissingTargetRetry(
-				webhookDB, webhookID, d,
-			)
+			e.failMissingTarget(webhookDB, webhookID, d)
 
 			return
 		}
@@ -1249,19 +1245,19 @@ func (e *Engine) failUnretryableRetry(
 	e.failDelivery(webhookDB, d, target.Type, reason)
 }
 
-// failMissingTargetRetry terminally fails an orphaned retrying
-// delivery whose target row is gone. Both restart recovery and the
-// periodic sweep call it, so the transition exists once.
+// failMissingTarget terminally fails a recovered delivery, pending or
+// retrying, whose target row is gone. Restart recovery and the periodic
+// sweep call it for both statuses, so the transition exists once.
 //
-// Until it existed both paths logged the failed lookup and returned,
-// which left the delivery retrying for the life of the database and
+// Until it existed those paths logged the failed lookup and moved on,
+// which left the delivery where it was for the life of the database and
 // the sweep repeating the same error every minute forever. Failing it
 // with a recorded reason is the treatment the other orphaned-retry
 // cases already get, so all of them read alike in the event log.
 //
 // Logged at warn rather than error: a deleted target is an operator
 // action, not a system fault.
-func (e *Engine) failMissingTargetRetry(
+func (e *Engine) failMissingTarget(
 	webhookDB *gorm.DB,
 	webhookID string,
 	d *database.Delivery,
@@ -1274,13 +1270,37 @@ func (e *Engine) failMissingTargetRetry(
 
 	defer e.inflight.release(d.ID)
 
+	// The batch was read before ownership was taken, and a worker may
+	// have settled the delivery and let it go in between. Only a row
+	// still in the status the batch read is failed.
+	row, err := e.loadDelivery(webhookDB, d.ID)
+	if err != nil {
+		e.log.Error(
+			"failed to load delivery",
+			"delivery_id", d.ID,
+			"error", err,
+		)
+
+		return
+	}
+
+	if row.Status != d.Status {
+		e.log.Debug(
+			"delivery already handled, not failed",
+			"delivery_id", d.ID,
+			"status", row.Status,
+		)
+
+		return
+	}
+
 	targetType, reason := e.missingTargetReason(d.TargetID)
 
 	e.log.Warn(
-		"failing orphaned retrying delivery: "+
-			"its target no longer exists",
+		"failing recovered delivery: its target no longer exists",
 		"webhook_id", webhookID,
 		"delivery_id", d.ID,
+		"status", d.Status,
 		"target_id", d.TargetID,
 		"target_type", targetType,
 	)
@@ -1314,15 +1334,14 @@ func (e *Engine) missingTargetReason(
 	if err != nil {
 		return "", fmt.Sprintf(
 			"target %s no longer exists; the delivery "+
-				"cannot be retried and has been failed "+
-				"terminally",
+				"has been failed terminally",
 			targetID,
 		)
 	}
 
 	return target.Type, fmt.Sprintf(
 		"target %q (type %s) was deleted; the delivery "+
-			"cannot be retried and has been failed terminally",
+			"has been failed terminally",
 		target.Name, target.Type,
 	)
 }
@@ -2021,13 +2040,30 @@ func (e *Engine) sendRecoveredDeliveries(
 
 		target, ok := targetMap[deliveries[i].TargetID]
 		if !ok {
-			e.log.Error(
-				"target not found for delivery",
-				"delivery_id", deliveries[i].ID,
-				"target_id", deliveries[i].TargetID,
-			)
+			// A missing entry does not mean the target is gone: the
+			// map is also empty when its query failed. Only a lookup
+			// that finds no row ends the delivery; any other error
+			// leaves it pending for the next sweep. See
+			// recoverSingleRetry.
+			var err error
 
-			continue
+			target, err = e.loadTarget(deliveries[i].TargetID)
+			if errors.Is(err, gorm.ErrRecordNotFound) {
+				e.failMissingTarget(webhookDB, webhookID, &deliveries[i])
+
+				continue
+			}
+
+			if err != nil {
+				e.log.Error(
+					"failed to load target for recovered delivery",
+					"delivery_id", deliveries[i].ID,
+					"target_id", deliveries[i].TargetID,
+					"error", err,
+				)
+
+				continue
+			}
 		}
 
 		if !e.takeForRedispatch(

internal/delivery/export_test.go

@@ -321,6 +321,16 @@ func (e *Engine) ExportRecoverRetryingDeliveries(
 	e.recoverRetryingDeliveries(webhookDB, webhookID)
 }
 
+// ExportFailMissingTarget exposes failMissingTarget, so a test can hand
+// it a delivery as a batch read it earlier.
+func (e *Engine) ExportFailMissingTarget(
+	webhookDB *gorm.DB,
+	webhookID string,
+	d *database.Delivery,
+) {
+	e.failMissingTarget(webhookDB, webhookID, d)
+}
+
 // ExportDeliveryCh returns the delivery channel.
 func (e *Engine) ExportDeliveryCh() chan Task {
 	return e.deliveryCh

internal/delivery/terminal_state_test.go

@@ -18,16 +18,17 @@ import (
 // https://git.eeqj.de/sneak/webhooker/issues/107: a delivery failed
 // with nothing in its event log to say why, and a retrying delivery
 // whose target was deleted, which used to keep sending and then never
-// terminalise.
+// terminalise. Section 4 is the same deleted-target gap for a pending
+// delivery: https://git.eeqj.de/sneak/webhooker/issues/293.
 
 // tUnknownType is a target type no build implements. It stands in for
 // a target whose type was written by a build that knew a type this one
 // does not.
 const tUnknownType = database.TargetType("pubsub")
 
-// tSeedDeletedTarget creates a target, a retrying delivery against it
-// with one recorded failed attempt, and then deletes the target the
-// way the source page does.
+// tSeedDeletedTarget creates a target, a delivery against it at the
+// given status with one recorded failed attempt, and then deletes the
+// target the way the source page does.
 //
 // It asserts the delete is soft, because that is the whole reason the
 // engine could not tell a deleted target from a target id that never
@@ -36,6 +37,7 @@ func tSeedDeletedTarget(
 	t *testing.T,
 	s iSetup,
 	name, url string,
+	status database.DeliveryStatus,
 ) string {
 	t.Helper()
 
@@ -51,8 +53,7 @@ func tSeedDeletedTarget(
 	)
 
 	d := iSeedDelivery(
-		t, s.WebhookDB, event.ID, targetID,
-		database.DeliveryStatusRetrying,
+		t, s.WebhookDB, event.ID, targetID, status,
 	)
 
 	iSeedFailedResult(t, s.WebhookDB, d.ID)
@@ -173,6 +174,7 @@ func TestRecoverSingleRetry_TargetDeleted(t *testing.T) {
 
 	deliveryID := tSeedDeletedTarget(
 		t, s, "gone-on-recovery", "http://example.com/hook",
+		database.DeliveryStatusRetrying,
 	)
 
 	s.Engine.ExportRecoverWebhookDeliveries(
@@ -210,6 +212,7 @@ func TestSweepSingleRetry_TargetDeleted(t *testing.T) {
 
 	deliveryID := tSeedDeletedTarget(
 		t, s, "gone-on-sweep", "http://example.com/hook",
+		database.DeliveryStatusRetrying,
 	)
 
 	// Twice, because the bug was an error the sweep repeated every
@@ -278,11 +281,11 @@ func TestSweepSingleRetry_TargetNeverExisted(t *testing.T) {
 	)
 }
 
-// TestFailMissingTargetRetry_WritesNoTargetRow holds the new terminal
-// path to the same rule as the existing one: no target row, and so no
+// TestFailMissingTarget_WritesNoTargetRow holds the new terminal path
+// to the same rule as the existing one: no target row, and so no
 // plaintext target config, may be written into the per-webhook event
 // database. See https://git.eeqj.de/sneak/webhooker/issues/206.
-func TestFailMissingTargetRetry_WritesNoTargetRow(
+func TestFailMissingTarget_WritesNoTargetRow(
 	t *testing.T,
 ) {
 	t.Parallel()
@@ -297,6 +300,7 @@ func TestFailMissingTargetRetry_WritesNoTargetRow(
 
 	deliveryID := tSeedDeletedTarget(
 		t, s, "credential-bearing", hookURL,
+		database.DeliveryStatusRetrying,
 	)
 
 	s.Engine.ExportSweepWebhookRetries(
@@ -529,3 +533,213 @@ func TestRecoverSingleRetry_TargetUnreadable_LeavesDeliveryAlone(
 
 	assert.Zero(t, s.Engine.ExportInflightHeld())
 }
+
+// --- 4. A pending delivery whose target is gone ---
+
+func TestRecoverPending_TargetDeleted(t *testing.T) {
+	t.Parallel()
+
+	s := newISetup(t)
+
+	deliveryID := tSeedDeletedTarget(
+		t, s, "gone-while-pending", "http://example.com/hook",
+		database.DeliveryStatusPending,
+	)
+
+	s.Engine.ExportRecoverWebhookDeliveries(
+		context.Background(), s.WebhookID,
+	)
+
+	iAssertStatus(
+		t, s.WebhookDB, deliveryID,
+		database.DeliveryStatusFailed,
+	)
+
+	last := tLastResult(t, s, deliveryID, 2)
+
+	assert.False(t, last.Success)
+	assert.Equal(t, 2, last.AttemptNum)
+	assert.Contains(t, last.Error, "gone-while-pending")
+	assert.Contains(t, last.Error, "was deleted")
+
+	assert.Empty(t, fDrain(s.Engine),
+		"a delivery whose target is gone was sent",
+	)
+	assert.Zero(t, s.Engine.ExportInflightHeld(),
+		"the terminal path leaked its ownership reference",
+	)
+}
+
+// TestRecoverPending_TargetDeleted_LeavesAnOwnedDeliveryAlone: the
+// terminal write takes ownership like every other recovery write, so a
+// delivery the engine still holds is not failed underneath its worker.
+func TestRecoverPending_TargetDeleted_LeavesAnOwnedDeliveryAlone(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	s := newISetup(t)
+
+	deliveryID := tSeedDeletedTarget(
+		t, s, "gone-but-owned", "http://example.com/hook",
+		database.DeliveryStatusPending,
+	)
+
+	require.True(t, s.Engine.ExportRetainDelivery(deliveryID))
+
+	s.Engine.ExportRecoverWebhookDeliveries(
+		context.Background(), s.WebhookID,
+	)
+
+	iAssertStatus(
+		t, s.WebhookDB, deliveryID,
+		database.DeliveryStatusPending,
+	)
+
+	assert.Len(t, iResults(t, s.WebhookDB, deliveryID), 1,
+		"a delivery the engine owns was failed underneath it",
+	)
+}
+
+// TestFailMissingTarget_LeavesASettledDeliveryAlone: the recovery paths
+// read their batch before taking ownership, and a worker may send a
+// delivery and let it go in between. The terminal write goes by the row
+// as it is now, not as the batch read it.
+func TestFailMissingTarget_LeavesASettledDeliveryAlone(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	s := newISetup(t)
+
+	deliveryID := tSeedDeletedTarget(
+		t, s, "gone-after-sending", "http://example.com/hook",
+		database.DeliveryStatusPending,
+	)
+
+	var batch database.Delivery
+
+	require.NoError(t, s.WebhookDB.First(
+		&batch, "id = ?", deliveryID,
+	).Error)
+
+	// A worker settles the delivery after the batch was read.
+	require.NoError(t, s.WebhookDB.Model(&database.Delivery{}).
+		Where("id = ?", deliveryID).
+		Update("status", database.DeliveryStatusDelivered).Error)
+
+	s.Engine.ExportFailMissingTarget(
+		s.WebhookDB, s.WebhookID, &batch,
+	)
+
+	iAssertStatus(
+		t, s.WebhookDB, deliveryID,
+		database.DeliveryStatusDelivered,
+	)
+
+	assert.Len(t, iResults(t, s.WebhookDB, deliveryID), 1,
+		"a delivery settled after the batch read was then failed",
+	)
+	assert.Zero(t, s.Engine.ExportInflightHeld())
+}
+
+// TestSweepPending_TargetDeleted sweeps twice over a batch that also
+// holds a healthy stranded delivery. The one whose target is gone is
+// failed once and then left alone; the healthy one is queued by the
+// first sweep and not again by the second.
+func TestSweepPending_TargetDeleted(t *testing.T) {
+	t.Parallel()
+
+	liveTargetID := uuid.New().String()
+	s := fSweepSetup(t, liveTargetID, "still-there")
+
+	deliveryID := tSeedDeletedTarget(
+		t, s, "gone-on-pending-sweep", "http://example.com/hook",
+		database.DeliveryStatusPending,
+	)
+	rAgePending(t, s.WebhookDB, deliveryID)
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"target":"live"}`,
+	)
+
+	healthy := iSeedDelivery(
+		t, s.WebhookDB, event.ID, liveTargetID,
+		database.DeliveryStatusPending,
+	)
+	rAgePending(t, s.WebhookDB, healthy.ID)
+
+	ctx := context.Background()
+
+	s.Engine.ExportSweepWebhookRetries(ctx, s.WebhookID)
+
+	tasks := fDrain(s.Engine)
+	require.Len(t, tasks, 1,
+		"the first sweep did not queue the healthy delivery",
+	)
+	assert.Equal(t, healthy.ID, tasks[0].DeliveryID)
+
+	s.Engine.ExportSweepWebhookRetries(ctx, s.WebhookID)
+
+	assert.Empty(t, fDrain(s.Engine),
+		"the second sweep queued a delivery again",
+	)
+
+	iAssertStatus(
+		t, s.WebhookDB, deliveryID,
+		database.DeliveryStatusFailed,
+	)
+
+	last := tLastResult(t, s, deliveryID, 2)
+
+	assert.Contains(t, last.Error, "gone-on-pending-sweep")
+	assert.Contains(t, last.Error, "was deleted")
+}
+
+// TestRecoverPending_TargetUnreadable_LeavesDeliveryAlone: a failed
+// read of the main database is not a deleted target. Restart recovery
+// holds every pending delivery of the webhook in one batch, so failing
+// on this would fail all of them.
+func TestRecoverPending_TargetUnreadable_LeavesDeliveryAlone(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	s := newISetup(t)
+
+	targetID := uuid.New().String()
+
+	iCreateTarget(
+		t, s.MainDB, targetID, s.WebhookID, "healthy",
+		database.TargetTypeLog, "", 0,
+	)
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"still":"pending"}`,
+	)
+
+	d := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	sqlDB, err := s.MainDB.DB()
+	require.NoError(t, err)
+	require.NoError(t, sqlDB.Close())
+
+	s.Engine.ExportRecoverPendingDeliveries(
+		context.Background(), s.WebhookDB, s.WebhookID,
+	)
+
+	iAssertStatus(
+		t, s.WebhookDB, d.ID,
+		database.DeliveryStatusPending,
+	)
+
+	assert.Empty(t, iResults(t, s.WebhookDB, d.ID),
+		"an unreadable main database produced a terminal "+
+			"failure row",
+	)
+	assert.Empty(t, fDrain(s.Engine))
+	assert.Zero(t, s.Engine.ExportInflightHeld())
+}