fix: prevent data race in querycoord collection notifier update (#45037)

Fixes #45035

This commit addresses a data race issue where refreshCollection was
updating the collection notifier without proper lock protection.

Changes:
- Add UpdateCollection method to CollectionManager with proper locking
- Introduce CollectionOperator pattern for thread-safe collection
updates
- Make setRefreshNotifier private and use it through the operator
pattern
- Update refreshCollection to use the new UpdateCollection method
- Handle collection not found error gracefully in refreshCollection

The CollectionOperator pattern ensures all collection modifications go
through the CollectionManager's lock, preventing concurrent access
issues.

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

internal/querycoordv2/meta/collection_manager.go

@@ -53,7 +53,7 @@ type Collection struct {
 	Schema          *schemapb.CollectionSchema
 }
 
-func (collection *Collection) SetRefreshNotifier(notifier chan struct{}) {
+func (collection *Collection) setRefreshNotifier(notifier chan struct{}) {
 	collection.mut.Lock()
 	defer collection.mut.Unlock()
 
@@ -576,6 +576,22 @@ func (m *CollectionManager) UpdateCollectionLoadPercent(ctx context.Context, col
 	return collectionPercent, m.putCollection(ctx, saveCollection, newCollection)
 }
 
+func (m *CollectionManager) UpdateCollection(ctx context.Context, collectionID int64, ops ...CollectionOperator) error {
+	m.rwmutex.Lock()
+	defer m.rwmutex.Unlock()
+
+	collection, ok := m.collections[collectionID]
+	if !ok {
+		return merr.WrapErrCollectionNotLoaded(collectionID)
+	}
+
+	for _, op := range ops {
+		op(collection)
+	}
+	m.collections[collectionID] = collection
+	return nil
+}
+
 // RemoveCollection removes collection and its partitions.
 func (m *CollectionManager) RemoveCollection(ctx context.Context, collectionID typeutil.UniqueID) error {
 	m.rwmutex.Lock()

internal/querycoordv2/meta/collection_operator.go

@@ -0,0 +1,27 @@
+// Licensed to the LF AI & Data foundation under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package meta
+
+// CollectionOperator is a function that can be used to modify a collection
+type CollectionOperator func(collection *Collection) (changed bool)
+
+func SetNotifierCollectionOp(notifier chan struct{}) CollectionOperator {
+	return func(collection *Collection) (changed bool) {
+		collection.setRefreshNotifier(notifier)
+		return true
+	}
+}

internal/querycoordv2/services.go

@@ -631,9 +631,13 @@ func (s *Server) refreshCollection(ctx context.Context, collectionID int64) erro
 		return err
 	}
 
-	collection.SetRefreshNotifier(readyCh)
+	err = s.meta.CollectionManager.UpdateCollection(ctx, collectionID, meta.SetNotifierCollectionOp(readyCh))
+	// if collection already released, treat as success
+	if errors.Is(err, merr.ErrCollectionNotFound) {
 		return nil
 	}
+	return err
+}
 
 // This is totally same to refreshCollection, remove it for now
 // refreshPartitions must be called after loading a collection. It looks for new segments that are not loaded yet and