Do not generate scheduled task with timestamp in the past

Author: Shaddoll

service/history/shard/context.go

@@ -1295,6 +1295,7 @@ func (s *contextImpl) allocateTimerIDsLocked(
 	workflowID string,
 	timerTasks []persistence.Task,
 ) error {
+	now := s.GetTimeSource().Now().Truncate(persistence.DBTimestampMinPrecision)
 	// assign IDs for the timer tasks. They need to be assigned under shard lock.
 	cluster := s.GetClusterMetadata().GetCurrentClusterName()
 	for _, task := range timerTasks {
@@ -1324,6 +1325,11 @@ func (s *contextImpl) allocateTimerIDsLocked(
 		}
 
 		readCursorTS := s.scheduledTaskMaxReadLevelMap[cluster]
+		// make sure scheduled task timestamp is higher than
+		// 1. max read level, so that queue processor can read the task back.
+		// 2. current time. Otherwise the task timestamp is in the past and causes aritical load latency in queue processor metrics.
+		// Above cases can happen if shard move and new host have a time SKU,
+		// or there is db write delay, or we are simply (re-)generating tasks for an old workflow.
 		if ts.Before(readCursorTS) {
 			// This can happen if shard move and new host have a time SKU, or there is db write delay.
 			// We generate a new timer ID using timerMaxReadLevel.
@@ -1336,6 +1342,14 @@ func (s *contextImpl) allocateTimerIDsLocked(
 				tag.ValueShardAllocateTimerBeforeRead)
 			ts = readCursorTS.Add(persistence.DBTimestampMinPrecision)
 		}
+		if ts.Before(now) {
+			s.logger.Warn("New timer generated is in the past",
+				tag.WorkflowDomainID(domainEntry.GetInfo().ID),
+				tag.WorkflowID(workflowID),
+				tag.Timestamp(ts),
+				tag.ValueShardAllocateTimerBeforeRead)
+			ts = now.Add(persistence.DBTimestampMinPrecision)
+		}
 		task.SetVisibilityTimestamp(ts)
 
 		seqNum, err := s.generateTaskIDLocked()

service/history/shard/context_test.go

@@ -1425,17 +1425,19 @@ func (s *contextTestSuite) TestAllocateTimerIDsLocked_WhenDomainIsActiveActiveUs
 }
 
 func (s *contextTestSuite) TestAllocateTimerIDsLocked_WhenTaskTimestampBeforeReadCursorAdjustsTimestamp() {
+	s.mockResource.TimeSource = clock.NewMockedTimeSourceAt(time.Now())
+	testTimeNow := s.mockResource.TimeSource.Now()
 	domainCacheEntry := s.setupAllocateTimerIDsTest()
 
 	// Set up scheduled task max read level map with read cursor ahead of task timestamp
 	// Use the actual current cluster name from cluster metadata
 	currentCluster := s.context.GetClusterMetadata().GetCurrentClusterName()
-	readCursor := time.Date(2025, 1, 1, 13, 0, 0, 0, time.UTC)
+	readCursor := testTimeNow.Add(time.Second)
 	s.context.scheduledTaskMaxReadLevelMap[currentCluster] = readCursor
 
 	task := s.createMockTimerTask(createMockTimerTaskParams{
 		Version:    constants.EmptyVersion,
-		Timestamp:  time.Date(2025, 1, 1, 12, 0, 0, 0, time.UTC), // before read cursor
+		Timestamp:  readCursor.Add(-time.Second), // before read cursor
 		DomainID:   testDomainID,
 		WorkflowID: testWorkflowID,
 		RunID:      "test-run-id",
@@ -1457,6 +1459,41 @@ func (s *contextTestSuite) TestAllocateTimerIDsLocked_WhenTaskTimestampBeforeRea
 		"Adjusted timestamp should match expected adjusted time")
 }
 
+func (s *contextTestSuite) TestAllocateTimerIDsLocked_WhenTaskTimestampBeforeNow() {
+	s.mockResource.TimeSource = clock.NewMockedTimeSourceAt(time.Now())
+	testTimeNow := s.mockResource.TimeSource.Now()
+	domainCacheEntry := s.setupAllocateTimerIDsTest()
+
+	// Set up scheduled task max read level map with read cursor ahead of task timestamp
+	// Use the actual current cluster name from cluster metadata
+	currentCluster := s.context.GetClusterMetadata().GetCurrentClusterName()
+	readCursor := testTimeNow.Add(-2 * time.Second) // read cursor is in the past
+	s.context.scheduledTaskMaxReadLevelMap[currentCluster] = readCursor
+
+	task := s.createMockTimerTask(createMockTimerTaskParams{
+		Version:    constants.EmptyVersion,
+		Timestamp:  readCursor.Add(-time.Second), // before now but after read cursor
+		DomainID:   testDomainID,
+		WorkflowID: testWorkflowID,
+		RunID:      "test-run-id",
+	})
+
+	err := s.context.allocateTimerIDsLocked(domainCacheEntry, testWorkflowID, []persistence.Task{task})
+
+	s.NoError(err)
+
+	// Verify timestamp was adjusted to be after read cursor
+	s.True(task.GetVisibilityTimestamp().After(readCursor),
+		"Task timestamp should be adjusted to be after read cursor")
+
+	// Verify it's the expected adjusted time (readCursor + DBTimestampMinPrecision)
+	expectedTime := testTimeNow.Add(persistence.DBTimestampMinPrecision)
+	actualTime := task.GetVisibilityTimestamp()
+	s.Equal(expectedTime.Truncate(persistence.DBTimestampMinPrecision),
+		actualTime.Truncate(persistence.DBTimestampMinPrecision),
+		"Adjusted timestamp should match expected adjusted time")
+}
+
 func (s *contextTestSuite) TestAllocateTimerIDsLocked_WhenClusterManagerLookupFailsReturnsError() {
 	// Create active-active domain cache entry
 	domainInfo := &persistence.DomainInfo{ID: testDomainID}