[ISSUE #974] ArrayIndexOutOfBoundsException may be thrown when invokes taskDispatcher.addTask

naming/src/main/java/com/alibaba/nacos/naming/consistency/ephemeral/distro/TaskDispatcher.java

@@ -17,10 +17,7 @@
 
 import com.alibaba.fastjson.JSON;
 import com.alibaba.nacos.naming.cluster.servers.Server;
-import com.alibaba.nacos.naming.misc.GlobalConfig;
-import com.alibaba.nacos.naming.misc.GlobalExecutor;
-import com.alibaba.nacos.naming.misc.Loggers;
-import com.alibaba.nacos.naming.misc.NetUtils;
+import com.alibaba.nacos.naming.misc.*;
 import org.apache.commons.lang3.StringUtils;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
@@ -58,12 +55,8 @@ public void init() {
         }
     }
 
-    public int mapTask(String key) {
-        return Math.abs(key.hashCode()) % partitionConfig.getTaskDispatchThreadCount();
-    }
-
     public void addTask(String key) {
-        taskSchedulerList.get(mapTask(key)).addTask(key);
+        taskSchedulerList.get(UtilsAndCommons.shakeUp(key, partitionConfig.getTaskDispatchThreadCount())).addTask(key);
     }
 
     public class TaskScheduler implements Runnable {

naming/src/main/java/com/alibaba/nacos/naming/misc/UtilsAndCommons.java

@@ -237,4 +237,34 @@ public static Map<String, String> parseMetadata(String metadata) throws NacosExc
     public static String assembleFullServiceName(String namespaceId, String serviceName) {
         return namespaceId + UtilsAndCommons.NAMESPACE_SERVICE_CONNECTOR + serviceName;
     }
+
+    /**
+     * 根据指定的字符串计算出一个0（含）到{@code upperLimit}（不含）之间的数字，本方法会试图让不同的字符串较均匀的分布在0到{@code upperLimit}之间。
+     * (Provide a number between 0(include) and {@code upperLimit}(exclude) for the given {@code string}, the number will be nearly uniform distribution.)
+     * <p>
+     * <p>
+     * 举个例子：假设有N个提供相同服务的服务器地址被存在一个数组中，为了实现负载均衡，可以根据调用者的名字决定使用哪个服务器。
+     * (e.g. Assume there's an array which contains some IP of the servers provide the same service, the caller name can be used to choose the server to achieve load balance.)
+     * <blockquote><pre>
+     *     String[] serverIps = new String[10];
+     *     int index = shakeUp("callerName", serverIps.length);
+     *     String targetServerIp = serverIps[index];
+     * </pre></blockquote>
+     *
+     * @param string     字符串。如果为null会固定返回0 (a string. the number 0 will be returned if it's null)
+     * @param upperLimit 返回值的上限，必须为正整数(>0) (the upper limit of the returned number, must be a positive integer, which means > 0)
+     * @return 0（含）到upperLimit（不含）之间的一个数字 (a number between 0(include) and upperLimit(exclude))
+     * @throws IllegalArgumentException if the upper limit equals or less than 0
+     * @since 1.0.0
+     */
+    public static int shakeUp(String string, int upperLimit) {
+        if (upperLimit < 1) {
+            throw new IllegalArgumentException("upper limit must be greater than 0");
+        }
+        if (string == null) {
+            return 0;
+        }
+        return (string.hashCode() & Integer.MAX_VALUE) % upperLimit;
+    }
+
 }

naming/src/test/java/com/alibaba/nacos/naming/consistency/ephemeral/distro/TaskDispatcherTest.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * 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.alibaba.nacos.naming.consistency.ephemeral.distro;
+
+import com.alibaba.nacos.naming.misc.GlobalConfig;
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.test.util.ReflectionTestUtils;
+
+/**
+ * @author jifengnan
+ */
+public class TaskDispatcherTest {
+
+    private TaskDispatcher taskDispatcher;
+
+    @Before
+    public void init() {
+        taskDispatcher = new TaskDispatcher();
+        GlobalConfig conf = new GlobalConfig();
+        ReflectionTestUtils.setField(conf, "taskDispatchThreadCount", 3);
+        ReflectionTestUtils.setField(taskDispatcher, "partitionConfig", conf);
+        taskDispatcher.init();
+    }
+
+    @Test
+    public void testAddTask() {
+        char[] chars = new char[]{2325, 9, 30, 12, 2};
+        taskDispatcher.addTask(new String(chars));
+    }
+}

naming/src/test/java/com/alibaba/nacos/naming/misc/UtilsAndCommonsTest.java

@@ -40,4 +40,16 @@ public void testControllerPathsDefaultValues() {
 
         Assert.assertEquals("/nacos/v1/ns", DEFAULT_NACOS_NAMING_CONTEXT);
     }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testShakeUpException() {
+        UtilsAndCommons.shakeUp(null, 0);
+    }
+
+    @Test
+    public void testShakeUp() {
+        Assert.assertEquals(0, UtilsAndCommons.shakeUp(null, 1));
+        char[] chars = new char[]{2325, 9, 30, 12, 2};
+        Assert.assertEquals(0, UtilsAndCommons.shakeUp(new String(chars), 1));
+    }
 }