Fix drop collection failed due to etcd txn limit. (#19362)

Signed-off-by: Nlongjiquan <jiquan.long@zilliz.com>
Signed-off-by: Nlongjiquan <jiquan.long@zilliz.com>

internal/metastore/kv/rootcoord/kv_catalog.go

@@ -373,8 +373,17 @@ func (kc *Catalog) DropCollection(ctx context.Context, collectionInfo *model.Col
 			fmt.Sprintf("%s/%s", CollectionAliasMetaPrefix, alias),
 		)
 	}
-	delMetakeysSnap = append(delMetakeysSnap, buildPartitionPrefix(collectionInfo.CollectionID))
-	delMetakeysSnap = append(delMetakeysSnap, buildFieldPrefix(collectionInfo.CollectionID))
+	// Snapshot will list all (k, v) pairs and then use Txn.MultiSave to save tombstone for these keys when it prepares
+	// to remove a prefix, so though we have very few prefixes, the final operations may exceed the max txn number.
+	// TODO(longjiquan): should we list all partitions & fields in KV anyway?
+	for _, partition := range collectionInfo.Partitions {
+		delMetakeysSnap = append(delMetakeysSnap, buildPartitionKey(collectionInfo.CollectionID, partition.PartitionID))
+	}
+	for _, field := range collectionInfo.Fields {
+		delMetakeysSnap = append(delMetakeysSnap, buildFieldKey(collectionInfo.CollectionID, field.FieldID))
+	}
+	// delMetakeysSnap = append(delMetakeysSnap, buildPartitionPrefix(collectionInfo.CollectionID))
+	// delMetakeysSnap = append(delMetakeysSnap, buildFieldPrefix(collectionInfo.CollectionID))
 
 	// Though batchMultiSaveAndRemoveWithPrefix is not atomic enough, we can promise atomicity outside.
 	// If we found collection under dropping state, we'll know that gc is not completely on this collection.

internal/rootcoord/drop_collection_task.go

@@ -86,7 +86,10 @@ func (t *dropCollectionTask) Execute(ctx context.Context) error {
 	redoTask.AddAsyncStep(&deleteCollectionMetaStep{
 		baseStep:     baseStep{core: t.core},
 		collectionID: collMeta.CollectionID,
-		ts:           ts,
+		// This ts is less than the ts when we notify data nodes to drop collection, but it's OK since we have already
+		// marked this collection as deleted. If we want to make this ts greater than the notification's ts, we should
+		// wrap a step who will have these three children and connect them with ts.
+		ts: ts,
 	})
 
 	return redoTask.Execute(ctx)

internal/rootcoord/drop_partition_task.go

@@ -82,7 +82,10 @@ func (t *dropPartitionTask) Execute(ctx context.Context) error {
 		baseStep:     baseStep{core: t.core},
 		collectionID: t.collMeta.CollectionID,
 		partitionID:  partID,
-		ts:           t.GetTs(),
+		// This ts is less than the ts when we notify data nodes to drop partition, but it's OK since we have already
+		// marked this partition as deleted. If we want to make this ts greater than the notification's ts, we should
+		// wrap a step who will have these children and connect them with ts.
+		ts: t.GetTs(),
 	})
 
 	return redoTask.Execute(ctx)

internal/rootcoord/garbage_collector.go

@@ -50,7 +50,10 @@ func (c *bgGarbageCollector) ReDropCollection(collMeta *model.Collection, ts Tim
 	redo.AddAsyncStep(&deleteCollectionMetaStep{
 		baseStep:     baseStep{core: c.s},
 		collectionID: collMeta.CollectionID,
-		ts:           ts,
+		// This ts is less than the ts when we notify data nodes to drop collection, but it's OK since we have already
+		// marked this collection as deleted. If we want to make this ts greater than the notification's ts, we should
+		// wrap a step who will have these three children and connect them with ts.
+		ts: ts,
 	})
 
 	// err is ignored since no sync steps will be executed.
@@ -94,7 +97,10 @@ func (c *bgGarbageCollector) ReDropPartition(pChannels []string, partition *mode
 		baseStep:     baseStep{core: c.s},
 		collectionID: partition.CollectionID,
 		partitionID:  partition.PartitionID,
-		ts:           ts,
+		// This ts is less than the ts when we notify data nodes to drop partition, but it's OK since we have already
+		// marked this partition as deleted. If we want to make this ts greater than the notification's ts, we should
+		// wrap a step who will have these children and connect them with ts.
+		ts: ts,
 	})
 
 	// err is ignored since no sync steps will be executed.

internal/rootcoord/meta_table.go

@@ -223,7 +223,6 @@ func (mt *MetaTable) RemoveCollection(ctx context.Context, collectionID UniqueID
 	if err := mt.catalog.DropCollection(ctx1, &model.Collection{CollectionID: collectionID, Aliases: aliases}, ts); err != nil {
 		return err
 	}
-	delete(mt.collID2Meta, collectionID)
 
 	var name string
 	coll, ok := mt.collID2Meta[collectionID]
@@ -236,6 +235,8 @@ func (mt *MetaTable) RemoveCollection(ctx context.Context, collectionID UniqueID
 		delete(mt.collAlias2ID, alias)
 	}
 
+	delete(mt.collID2Meta, collectionID)
+
 	log.Info("remove collection", zap.String("name", name), zap.Int64("id", collectionID), zap.Strings("aliases", aliases))
 	return nil
 }

internal/rootcoord/step.go

@@ -198,6 +198,8 @@ type waitForTsSyncedStep struct {
 func (s *waitForTsSyncedStep) Execute(ctx context.Context) ([]nestedStep, error) {
 	syncedTs := s.core.chanTimeTick.getSyncedTimeTick(s.channel)
 	if syncedTs < s.ts {
+		// TODO: there may be frequent log here.
+		// time.Sleep(Params.ProxyCfg.TimeTickInterval)
 		return nil, fmt.Errorf("ts not synced yet, channel: %s, synced: %d, want: %d", s.channel, syncedTs, s.ts)
 	}
 	return nil, nil

internal/rootcoord/step_executor.go

@@ -95,7 +95,7 @@ type bgStepExecutor struct {
 	bufferedSteps map[*stepStack]struct{}
 	selector      selectStepPolicy
 	mu            sync.Mutex
-	notify        chan struct{}
+	notifyChan    chan struct{}
 	interval      time.Duration
 }
 
@@ -108,7 +108,7 @@ func newBgStepExecutor(ctx context.Context, opts ...bgOpt) *bgStepExecutor {
 		bufferedSteps: make(map[*stepStack]struct{}),
 		selector:      defaultSelectPolicy(),
 		mu:            sync.Mutex{},
-		notify:        make(chan struct{}, 1),
+		notifyChan:    make(chan struct{}, 1),
 		interval:      defaultBgExecutingInterval,
 	}
 	for _, opt := range opts {
@@ -128,14 +128,8 @@ func (bg *bgStepExecutor) Stop() {
 }
 
 func (bg *bgStepExecutor) AddSteps(s *stepStack) {
-	bg.mu.Lock()
 	bg.addStepsInternal(s)
-	bg.mu.Unlock()
-
-	select {
-	case bg.notify <- struct{}{}:
-	default:
-	}
+	bg.notify()
 }
 
 func (bg *bgStepExecutor) process(steps []*stepStack) {
@@ -150,7 +144,8 @@ func (bg *bgStepExecutor) process(steps []*stepStack) {
 			defer wg.Done()
 			child := s.Execute(bg.ctx)
 			if child != nil {
-				bg.AddSteps(child)
+				// don't notify, wait for reschedule.
+				bg.addStepsInternal(child)
 			}
 		}()
 	}
@@ -161,7 +156,7 @@ func (bg *bgStepExecutor) schedule() {
 	bg.mu.Lock()
 	selected := bg.selector(bg.bufferedSteps)
 	for _, s := range selected {
-		bg.removeStepsInternal(s)
+		bg.unlockRemoveSteps(s)
 	}
 	bg.mu.Unlock()
 
@@ -178,7 +173,7 @@ func (bg *bgStepExecutor) scheduleLoop() {
 		select {
 		case <-bg.ctx.Done():
 			return
-		case <-bg.notify:
+		case <-bg.notifyChan:
 			bg.schedule()
 		case <-ticker.C:
 			bg.schedule()
@@ -187,9 +182,22 @@ func (bg *bgStepExecutor) scheduleLoop() {
 }
 
 func (bg *bgStepExecutor) addStepsInternal(s *stepStack) {
+	bg.mu.Lock()
+	bg.unlockAddSteps(s)
+	bg.mu.Unlock()
+}
+
+func (bg *bgStepExecutor) unlockAddSteps(s *stepStack) {
 	bg.bufferedSteps[s] = struct{}{}
 }
 
-func (bg *bgStepExecutor) removeStepsInternal(s *stepStack) {
+func (bg *bgStepExecutor) unlockRemoveSteps(s *stepStack) {
 	delete(bg.bufferedSteps, s)
 }
+
+func (bg *bgStepExecutor) notify() {
+	select {
+	case bg.notifyChan <- struct{}{}:
+	default:
+	}
+}

internal/rootcoord/step_test.go

+package rootcoord
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_waitForTsSyncedStep_Execute(t *testing.T) {
+	//Params.InitOnce()
+	//Params.ProxyCfg.TimeTickInterval = time.Millisecond
+
+	ticker := newRocksMqTtSynchronizer()
+	core := newTestCore(withTtSynchronizer(ticker))
+	core.chanTimeTick.syncedTtHistogram.update("ch1", 100)
+	s := &waitForTsSyncedStep{
+		baseStep: baseStep{core: core},
+		ts:       101,
+		channel:  "ch1",
+	}
+	children, err := s.Execute(context.Background())
+	assert.Equal(t, 0, len(children))
+	assert.Error(t, err)
+	core.chanTimeTick.syncedTtHistogram.update("ch1", 102)
+	children, err = s.Execute(context.Background())
+	assert.Equal(t, 0, len(children))
+	assert.NoError(t, err)
+}