fix checksum bug #2401

naming/src/main/java/com/alibaba/nacos/naming/core/Instances.java

@@ -39,16 +39,17 @@
  */
 public class Instances implements Record {
 
-    private static MessageDigest MESSAGE_DIGEST;
-
-    static {
-        try {
-            MESSAGE_DIGEST = MessageDigest.getInstance("MD5");
-        } catch (NoSuchAlgorithmException e) {
-            Loggers.SRV_LOG.error("error while calculating checksum(md5) for instances", e);
-            MESSAGE_DIGEST = null;
+    private static ThreadLocal<MessageDigest> MESSAGE_DIGEST_LOCAL = new ThreadLocal<MessageDigest>() {
+        @Override
+        protected MessageDigest initialValue() {
+            try {
+                return MessageDigest.getInstance("MD5");
+            } catch (NoSuchAlgorithmException e) {
+                Loggers.SRV_LOG.error("error while calculating checksum(md5) for instances", e);
+                return null;
+            }
         }
-    }
+    };
 
     private List<Instance> instanceList = new ArrayList<>();
 
@@ -83,9 +84,10 @@ private String recalculateChecksum() {
             sb.append(",");
         }
 
-        if (MESSAGE_DIGEST != null) {
-            checksum =
-                new BigInteger(1, MESSAGE_DIGEST.digest((sb.toString()).getBytes(Charset.forName("UTF-8")))).toString(16);
+        if (MESSAGE_DIGEST_LOCAL.get() != null) {
+            checksum = new BigInteger(1,
+                    MESSAGE_DIGEST_LOCAL.get().digest((sb.toString()).getBytes(Charset.forName("UTF-8"))))
+                    .toString(16);
         } else {
             checksum = RandomStringUtils.randomAscii(32);
         }

naming/src/test/java/com/alibaba/nacos/naming/core/InstancesTest.java

@@ -0,0 +1,112 @@
+/*
+ * 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.core;
+
+import org.junit.Test;
+
+import java.math.BigInteger;
+import java.nio.charset.Charset;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * @author lkxiaolou
+ */
+public class InstancesTest {
+
+    private static MessageDigest MESSAGE_DIGEST;
+
+    static {
+        try {
+            MESSAGE_DIGEST = MessageDigest.getInstance("MD5");
+        } catch (NoSuchAlgorithmException e) {
+            MESSAGE_DIGEST = null;
+        }
+    }
+
+    private static ThreadLocal<MessageDigest> MESSAGE_DIGEST_LOCAL = new ThreadLocal<MessageDigest>() {
+        @Override
+        protected MessageDigest initialValue() {
+            try {
+                return MessageDigest.getInstance("MD5");
+            } catch (NoSuchAlgorithmException e) {
+                return null;
+            }
+        }
+    };
+
+    @Test
+    public void checkSumNotThreadSafe() throws Exception {
+
+        final AtomicBoolean catchException = new AtomicBoolean(false);
+        CountDownLatch countDownLatch = new CountDownLatch(4);
+
+        for (int i = 0; i < 4; i++) {
+            Thread thread = new Thread(new Runnable() {
+                @Override
+                public void run() {
+                    while (true) {
+                        if (catchException.get()) {
+                            break;
+                        }
+                        try {
+                            checkSumThreadNotSafeVersion("test");
+                        } catch (ArrayIndexOutOfBoundsException e) {
+                            catchException.set(true);
+                        }
+                    }
+                    countDownLatch.countDown();
+                }
+            });
+            thread.start();
+        }
+
+        countDownLatch.await();
+
+        assert catchException.get();
+    }
+
+    //@Test
+    // 跑起来比较久，所以注释掉
+    public void checkSumThreadSafe() throws Exception {
+
+        CountDownLatch countDownLatch = new CountDownLatch(4);
+
+        for (int i = 0; i < 4; i++) {
+            Thread thread = new Thread(new Runnable() {
+                @Override
+                public void run() {
+                    for (int j = 0; j < Integer.MAX_VALUE; j++) {
+                        checkSumThreadSafeVersion("test");
+                    }
+                    countDownLatch.countDown();
+                }
+            });
+            thread.start();
+        }
+        countDownLatch.await();
+    }
+
+    private String checkSumThreadNotSafeVersion(String checkString) {
+        return new BigInteger(1, MESSAGE_DIGEST.digest((checkString).getBytes(Charset.forName("UTF-8")))).toString(16);
+    }
+
+    private String checkSumThreadSafeVersion(String checkString) {
+        return new BigInteger(1, MESSAGE_DIGEST_LOCAL.get().digest((checkString).getBytes(Charset.forName("UTF-8")))).toString(16);
+    }
+}