diff --git a/protocol/src/main/java/com/zfoo/protocol/collection/concurrent/CopyOnWriteHashMap.java b/protocol/src/main/java/com/zfoo/protocol/collection/concurrent/CopyOnWriteHashMap.java
new file mode 100644
index 00000000..4fadaa4a
--- /dev/null
+++ b/protocol/src/main/java/com/zfoo/protocol/collection/concurrent/CopyOnWriteHashMap.java
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2020 The zfoo 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 com.zfoo.protocol.collection.concurrent;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * @author godotg
+ */
+public class CopyOnWriteHashMap<K, V> implements Map<K, V> {
+
+    private final ReentrantLock lock = new ReentrantLock();
+    private volatile HashMap<K, V> map;
+
+    public CopyOnWriteHashMap() {
+        map = new HashMap<>();
+    }
+
+    public CopyOnWriteHashMap(int initialCapacity) {
+        map = new HashMap<>(initialCapacity);
+    }
+
+    private HashMap<K, V> newCopyMap() {
+        var newMap = new HashMap<K,V>();
+        newMap.putAll(map);
+        return newMap;
+    }
+
+    private void setNewMap(HashMap<K, V> newMap) {
+        map = newMap;
+    }
+
+    @Override
+    public int size() {
+        return map.size();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return map.isEmpty();
+    }
+
+    @Override
+    public boolean containsKey(Object key) {
+        return map.containsKey(key);
+    }
+
+    @Override
+    public boolean containsValue(Object value) {
+        return map.containsValue(value);
+    }
+
+    @Override
+    public V get(Object key) {
+        return map.get(key);
+    }
+
+
+    @Override
+    public V put(K key, V value) {
+        lock.lock();
+        try {
+            var newMap = newCopyMap();
+            var oldValue = newMap.put(key, value);
+            setNewMap(newMap);
+            return oldValue;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public V remove(Object key) {
+        lock.lock();
+        try {
+            var newMap = newCopyMap();
+            var oldValue = newMap.remove(key);
+            setNewMap(newMap);
+            return oldValue;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public void putAll(Map<? extends K, ? extends V> m) {
+        lock.lock();
+        try {
+            var newMap = newCopyMap();
+            newMap.putAll(m);
+            setNewMap(newMap);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public void clear() {
+        lock.lock();
+        try {
+            var newMap = newCopyMap();
+            setNewMap(newMap);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    public Set<K> keySet() {
+        return map.keySet();
+    }
+
+    @Override
+    public Collection<V> values() {
+        return map.values();
+    }
+
+    @Override
+    public Set<Entry<K, V>> entrySet() {
+        return map.entrySet();
+    }
+}