Copilot commented on code in PR #3612:
URL: https://github.com/apache/dubbo-go/pull/3612#discussion_r3788385437
##########
config_center/zookeeper/listener.go:
##########
@@ -58,31 +88,157 @@ func (l *CacheListener) AddListener(key string, listener
config_center.Configura
listeners.(map[config_center.ConfigurationListener]struct{})[listener] =
struct{}{}
l.keyListeners.Store(key, listeners)
}
+ if l.cache != nil {
+ l.cache.promoteWatch(key)
+ }
+}
+
+func (l *CacheListener) restoreBusinessWatches() {
+ if l.cache == nil || !l.cache.enabled() || l.zkEventListener == nil ||
+ l.zkEventListener.Client == nil ||
l.zkEventListener.Client.Conn == nil {
+ return
+ }
Review Comment:
`restoreBusinessWatches` returns early when `cache-ttl` disables the cache
(`!l.cache.enabled()`). ZooKeeper reconnects still invalidate *all* watches
(including those created by `AddListener`), so with cache disabled listeners
may stop receiving updates after a reconnect because no re-registration happens
(see `config_center/zookeeper/impl.go:345-351`).
##########
config_center/zookeeper/config_cache.go:
##########
@@ -0,0 +1,433 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) 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 zookeeper
+
+import (
+ "sync"
+ "time"
+)
+
+import (
+ "github.com/dubbogo/go-zookeeper/zk"
+
+ "github.com/hashicorp/golang-lru"
+)
+
+const (
+ pathLockShardCount = 128
+ maxCacheEntries = 1024
+ maxAutoWatches = 1024
+)
+
+type configCacheEntry struct {
+ content string
+ exists bool
+ expiresAt time.Time
+}
+
+type configWatchState struct {
+ watcher *zk.Watcher
+ auto bool
+ pending bool
+}
+
+func (s configWatchState) tracked() bool {
+ return s.watcher != nil || s.pending
+}
+
+func (s configWatchState) holdsAutoSlot() bool {
+ return s.auto && s.tracked()
+}
+
+func (s configWatchState) holdsAutoWatch() bool {
+ return s.auto && s.watcher != nil
+}
+
+func (s configWatchState) holdsAutoReservation() bool {
+ return s.auto && s.pending
+}
+
+type configCache struct {
+ ttl time.Duration
+
+ stateLock sync.RWMutex
+ entries *lru.Cache
+ watches map[string]configWatchState
+ autoWatchCount int
+ autoWatchReservations int
+ generation uint64
+
+ pathLocks [pathLockShardCount]sync.Mutex
+}
+
+func newConfigCache(ttl time.Duration) configCache {
+ entries, err := lru.New(maxCacheEntries)
+ if err != nil {
+ panic(err)
+ }
+ return configCache{
+ ttl: ttl,
+ entries: entries,
+ watches: make(map[string]configWatchState),
+ }
+}
+
+func (c *configCache) enabled() bool {
+ return c.ttl > 0
+}
+
+func (c *configCache) load(
+ path string,
+ loader func(*zk.Watcher, bool) (configCacheEntry, *zk.Watcher, error),
+ removeWatcher func(*zk.Watcher),
+) (configCacheEntry, error) {
+ if !c.enabled() {
+ entry, _, err := loader(nil, false)
+ return entry, err
+ }
+ if entry, ok := c.getFresh(path); ok {
+ return entry, nil
+ }
+
+ pathLock := c.pathLock(path)
+ pathLock.Lock()
+ defer pathLock.Unlock()
+
+ for {
+ if entry, ok := c.getFresh(path); ok {
+ return entry, nil
+ }
+
+ generation, watchState, registerWatch := c.prepareLoad(path)
+ entry, watcher, err := loader(watchState.watcher, registerWatch)
+ nextWatchState := watchState
+ if registerWatch {
+ nextWatchState = configWatchState{}
+ if watcher != nil {
+ nextWatchState = configWatchState{watcher:
watcher, auto: true}
+ }
+ }
+ if err != nil {
+ if !c.storeWatchState(path, generation, nextWatchState)
{
+ if registerWatch {
+ removeRegisteredWatcher(removeWatcher,
watcher)
+ }
+ continue
+ }
+ return configCacheEntry{}, err
+ }
+ if !c.storeLoad(path, generation, entry, nextWatchState) {
+ if registerWatch {
+ removeRegisteredWatcher(removeWatcher, watcher)
+ }
+ continue
+ }
+ return entry, nil
+ }
+}
+
+func (c *configCache) prepareLoad(path string) (uint64, configWatchState,
bool) {
+ c.stateLock.Lock()
+ defer c.stateLock.Unlock()
+
+ generation := c.generation
+ watchState := c.watches[path]
+ if watchState.tracked() {
+ return generation, watchState, false
+ }
+
+ pendingState := configWatchState{auto: true, pending: true}
+ if !c.setWatchStateLocked(path, pendingState) {
+ return generation, configWatchState{}, false
+ }
+ return generation, pendingState, true
+}
+
+func (c *configCache) store(path string, entry configCacheEntry) {
+ if !c.enabled() {
+ return
+ }
+ pathLock := c.pathLock(path)
+ pathLock.Lock()
+ defer pathLock.Unlock()
+
+ c.stateLock.Lock()
+ defer c.stateLock.Unlock()
+ c.storeEntryLocked(path, entry)
+}
+
+func (c *configCache) storeAtGeneration(path string, generation uint64, entry
configCacheEntry) {
+ if !c.enabled() {
+ return
+ }
+ pathLock := c.pathLock(path)
+ pathLock.Lock()
+ defer pathLock.Unlock()
+
+ c.stateLock.Lock()
+ defer c.stateLock.Unlock()
+ if c.generation == generation {
+ c.storeEntryLocked(path, entry)
+ }
+}
+
+func (c *configCache) getFresh(path string) (configCacheEntry, bool) {
+ c.stateLock.RLock()
+ defer c.stateLock.RUnlock()
+
+ value, ok := c.entries.Get(path)
+ if !ok {
+ return configCacheEntry{}, false
+ }
+ entry := value.(configCacheEntry)
+ if !entry.expiresAt.After(time.Now()) {
+ c.entries.Remove(path)
+ return configCacheEntry{}, false
+ }
+ return entry, true
+}
Review Comment:
`getFresh` holds `stateLock.RLock()` but removes from `c.entries` when the
entry is expired. That mutates shared state under a read lock and can race with
concurrent readers/writers (HashiCorp `lru.Cache` is not concurrency-safe
without external locking), potentially causing data races or panics.
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