This is an automated cherry-pick of #10042

ref #9764

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

Author: lhy1024

pkg/mcs/scheduling/server/affinity/watcher.go

@@ -0,0 +1,165 @@
+// Copyright 2026 TiKV Project Authors.
+//
+// Licensed 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 affinity
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"sync"
+
+	"go.etcd.io/etcd/api/v3/mvccpb"
+	clientv3 "go.etcd.io/etcd/client/v3"
+	"go.uber.org/zap"
+
+	"github.com/pingcap/log"
+
+	"github.com/tikv/pd/pkg/schedule/affinity"
+	"github.com/tikv/pd/pkg/schedule/labeler"
+	"github.com/tikv/pd/pkg/utils/etcdutil"
+	"github.com/tikv/pd/pkg/utils/keypath"
+)
+
+// Watcher is used to watch the affinity group and label rule changes from PD.
+// It watches two paths:
+// affinityGroupsPrefix:
+//   - Key: /pd/{cluster_id}/affinity_groups/{group_id}
+//   - Value: affinity.Group
+//
+// regionLabelPathPrefix:
+//   - Key: /pd/{cluster_id}/region_label/affinity_group/{group_id}
+//   - Value: labeler.LabelRule
+//   - Filtered to only process rules with ID prefix "affinity_group/"
+type Watcher struct {
+	cancel     context.CancelFunc
+	wg         *sync.WaitGroup
+	etcdClient *clientv3.Client
+
+	// affinityManager is used to manage the affinity groups in the scheduling server.
+	affinityManager *affinity.Manager
+
+	groupWatcher *etcdutil.LoopWatcher
+	labelWatcher *etcdutil.LoopWatcher
+}
+
+// NewWatcher creates a new watcher to watch the affinity changes from PD.
+func NewWatcher(
+	ctx context.Context,
+	etcdClient *clientv3.Client,
+	affinityManager *affinity.Manager,
+) (*Watcher, error) {
+	ctx, cancel := context.WithCancel(ctx)
+	w := &Watcher{
+		cancel:          cancel,
+		wg:              &sync.WaitGroup{},
+		etcdClient:      etcdClient,
+		affinityManager: affinityManager,
+	}
+	err := w.initializeGroupWatcher(ctx)
+	if err != nil {
+		w.Close()
+		return nil, err
+	}
+	err = w.initializeAffinityLabelWatcher(ctx)
+	if err != nil {
+		w.Close()
+		return nil, err
+	}
+	return w, nil
+}
+
+// initializeGroupWatcher initializes the watcher for affinity group changes.
+func (w *Watcher) initializeGroupWatcher(ctx context.Context) error {
+	putFn := func(kv *mvccpb.KeyValue) error {
+		log.Info("update affinity group", zap.String("key", string(kv.Key)), zap.String("value", string(kv.Value)))
+		group := &affinity.Group{}
+		if err := json.Unmarshal(kv.Value, group); err != nil {
+			log.Warn("failed to unmarshal affinity group", zap.String("key", string(kv.Key)), zap.Error(err))
+			return err
+		}
+		w.affinityManager.SyncGroupFromEtcd(group)
+		return nil
+	}
+
+	deleteFn := func(kv *mvccpb.KeyValue) error {
+		key := string(kv.Key)
+		log.Info("delete affinity group", zap.String("key", key))
+		groupID := strings.TrimPrefix(key, keypath.AffinityGroupsPrefix())
+		w.affinityManager.SyncGroupDeleteFromEtcd(groupID)
+		return nil
+	}
+
+	w.groupWatcher = etcdutil.NewLoopWatcher(
+		ctx, w.wg,
+		w.etcdClient,
+		"scheduling-affinity-group-watcher",
+		strings.TrimSuffix(keypath.AffinityGroupsPrefix(), "/"),
+		func([]*clientv3.Event) error { return nil },
+		putFn, deleteFn,
+		func([]*clientv3.Event) error { return nil },
+		true, /* withPrefix */
+	)
+	w.groupWatcher.StartWatchLoop()
+	return w.groupWatcher.WaitLoad()
+}
+
+// initializeAffinityLabelWatcher initializes the watcher for affinity label rule changes.
+// It watches the region_label path but only processes rules with affinity group prefix.
+func (w *Watcher) initializeAffinityLabelWatcher(ctx context.Context) error {
+	// Note: labelWatcher does not need preEventsFn/postEventsFn locking
+	// because the sync methods will handle locking internally
+
+	putFn := func(kv *mvccpb.KeyValue) error {
+		key := string(kv.Key)
+		log.Info("update affinity label rule", zap.String("key", key), zap.String("value", string(kv.Value)))
+		rule, err := labeler.NewLabelRuleFromJSON(kv.Value)
+		if err != nil {
+			log.Warn("failed to unmarshal affinity label rule", zap.String("key", key), zap.Error(err))
+			return err
+		}
+		return w.affinityManager.SyncKeyRangesFromEtcd(rule)
+	}
+
+	deleteFn := func(kv *mvccpb.KeyValue) error {
+		key := string(kv.Key)
+		log.Info("delete affinity label rule", zap.String("key", key))
+		ruleID := strings.TrimPrefix(key, keypath.RegionLabelPathPrefix())
+		w.affinityManager.SyncKeyRangesDeleteFromEtcd(ruleID)
+		return nil
+	}
+
+	w.labelWatcher = etcdutil.NewLoopWatcher(
+		ctx, w.wg,
+		w.etcdClient,
+		"scheduling-affinity-label-watcher",
+		strings.TrimSuffix(keypath.RegionLabelKeyPath(affinity.LabelRuleIDPrefix), "/"), // Filter: only process affinity group label rules
+		func([]*clientv3.Event) error { return nil },
+		putFn, deleteFn,
+		func([]*clientv3.Event) error { return nil },
+		true, /* withPrefix */
+	)
+	w.labelWatcher.StartWatchLoop()
+	return w.labelWatcher.WaitLoad()
+}
+
+// Close closes the watcher.
+func (w *Watcher) Close() {
+	if w.cancel != nil {
+		w.cancel()
+	}
+	if w.wg != nil {
+		w.wg.Wait()
+	}
+}