ttl: reschedule task to other instances when shriking worker

Author: lcwangchao

pkg/ttl/ttlworker/del.go

@@ -22,6 +22,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/pingcap/log"
 	"github.com/pingcap/tidb/pkg/sessionctx/variable"
 	"github.com/pingcap/tidb/pkg/ttl/cache"
 	"github.com/pingcap/tidb/pkg/ttl/metrics"
@@ -94,12 +95,12 @@ func (t *ttlDeleteTask) doDelete(ctx context.Context, rawSe session.Session) (re
 	leftRows := t.rows
 	defer func() {
 		if len(leftRows) > 0 {
-			t.statistics.IncErrorRows(len(leftRows))
+			retryRows = append(retryRows, leftRows...)
 		}
 	}()
 
 	se := newTableSession(rawSe, t.tbl, t.expire)
-	for len(leftRows) > 0 {
+	for len(leftRows) > 0 && ctx.Err() == nil {
 		maxBatch := variable.TTLDeleteBatchSize.Load()
 		var delBatch [][]types.Datum
 		if int64(len(leftRows)) < maxBatch {
@@ -133,7 +134,6 @@ func (t *ttlDeleteTask) doDelete(ctx context.Context, rawSe session.Session) (re
 		sqlInterval := time.Since(sqlStart)
 		if err != nil {
 			metrics.DeleteErrorDuration.Observe(sqlInterval.Seconds())
-			needRetry = needRetry && ctx.Err() == nil
 			logutil.BgLogger().Warn(
 				"delete SQL in TTL failed",
 				zap.Error(err),
@@ -214,6 +214,11 @@ func (b *ttlDelRetryBuffer) DoRetry(do func(*ttlDeleteTask) [][]types.Datum) tim
 	return b.retryInterval
 }
 
+// SetRetryInterval sets the retry interval of the buffer.
+func (b *ttlDelRetryBuffer) SetRetryInterval(interval time.Duration) {
+	b.retryInterval = interval
+}
+
 // Drain drains a retry buffer.
 func (b *ttlDelRetryBuffer) Drain() {
 	for ele := b.list.Front(); ele != nil; ele = ele.Next() {
@@ -296,8 +301,37 @@ func (w *ttlDeleteWorker) loop() error {
 	timer := time.NewTimer(w.retryBuffer.retryInterval)
 	defer timer.Stop()
 
-	// drain retry buffer to make sure the statistics are correct
-	defer w.retryBuffer.Drain()
+	defer func() {
+		// Have a final try to delete all rows in retry buffer while the worker stops
+		// to avoid leaving any TTL rows undeleted when shrinking the delete worker.
+		if w.retryBuffer.Len() > 0 {
+			start := time.Now()
+			log.Info(
+				"try to delete TTL rows in del worker buffer immediately because the worker is going to stop",
+				zap.Int("bufferLen", w.retryBuffer.Len()),
+			)
+			retryCtx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+			defer cancel()
+			w.retryBuffer.SetRetryInterval(0)
+			w.retryBuffer.DoRetry(func(task *ttlDeleteTask) [][]types.Datum {
+				return task.doDelete(retryCtx, se)
+			})
+			log.Info(
+				"delete TTL rows in del worker buffer finished",
+				zap.Duration("duration", time.Since(start)),
+			)
+		}
+
+		// drain retry buffer to make sure the statistics are correct
+		if w.retryBuffer.Len() > 0 {
+			log.Warn(
+				"some TTL rows are still in the buffer while the worker is going to stop, mark them as error",
+				zap.Int("bufferLen", w.retryBuffer.Len()),
+			)
+			w.retryBuffer.Drain()
+		}
+	}()
+
 	for w.Status() == workerStatusRunning {
 		tracer.EnterPhase(metrics.PhaseIdle)
 		select {

pkg/ttl/ttlworker/scan.go

@@ -85,6 +85,9 @@ type ttlScanTaskExecResult struct {
 	time time.Time
 	task *ttlScanTask
 	err  error
+	// interruptedByWorkerStop indicates whether the task has to stop for the worker stops.
+	// when it is true, we should reschedule this task in another worker or TiDB again.
+	interruptedByWorkerStop bool
 }
 
 func (t *ttlScanTask) result(err error) *ttlScanTaskExecResult {
@@ -99,6 +102,17 @@ func (t *ttlScanTask) getDatumRows(rows []chunk.Row) [][]types.Datum {
 	return datums
 }
 
+func (t *ttlScanTask) taskLogger(l *zap.Logger) *zap.Logger {
+	return l.With(
+		zap.String("jobID", t.JobID),
+		zap.Int64("scanID", t.ScanID),
+		zap.Int64("tableID", t.TableID),
+		zap.String("db", t.tbl.Schema.O),
+		zap.String("table", t.tbl.Name.O),
+		zap.String("partition", t.tbl.Partition.O),
+	)
+}
+
 func (t *ttlScanTask) doScan(ctx context.Context, delCh chan<- *ttlDeleteTask, sessPool util.SessionPool) *ttlScanTaskExecResult {
 	// TODO: merge the ctx and the taskCtx in ttl scan task, to allow both "cancel" and gracefully stop workers
 	// now, the taskCtx is only check at the beginning of every loop
@@ -121,13 +135,7 @@ func (t *ttlScanTask) doScan(ctx context.Context, delCh chan<- *ttlDeleteTask, s
 		case <-doScanFinished.Done():
 			return
 		}
-		logger := logutil.BgLogger().With(
-			zap.Int64("tableID", t.TableID),
-			zap.String("table", t.tbl.Name.O),
-			zap.String("partition", t.tbl.Partition.O),
-			zap.String("jobID", t.JobID),
-			zap.Int64("scanID", t.ScanID),
-		)
+		logger := t.taskLogger(logutil.BgLogger())
 		logger.Info("kill the running statement in scan task because the task or worker cancelled")
 		rawSess.KillStmt()
 		ticker := time.NewTicker(time.Minute)