ZOOKEEPER-3994: Disconnect reason is wrong for NOT_READ_ONLY_CLIENT and CLIENT_ZXID_AHEAD

Author: huangwenbo04 <huangwenbo04@meituan.com>

Reviewers: eolivelli@apache.org, andor@apache.org

Closes #1525 from nsnhuang/ZOOKEEPER-3994 and squashes the following commits:

578c4d730 [huangwenbo04] checkstyle
aaa5430b9 [huangwenbo04] use assertThrows() method instead of try-catch
0c35eb487 [huangwenbo04] make ServerCnxn.CloseRequestException public
fb4a18eeb [huangwenbo04] add approved licenses And fix checkstyle errors
dfe0c576f [huangwenbo04] DisconnectReason.CLIENT_ZXID_AHEAD test case
406af2279 [huangwenbo04] add comments
2f4efae70 [huangwenbo04] add test case
61a815af6 [huangwenbo04] disconnect reason wrong

zookeeper-server/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java

@@ -1394,7 +1394,7 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
         if (!readOnly && this instanceof ReadOnlyZooKeeperServer) {
             String msg = "Refusing session request for not-read-only client " + cnxn.getRemoteSocketAddress();
             LOG.info(msg);
-            throw new CloseRequestException(msg, ServerCnxn.DisconnectReason.CLIENT_ZXID_AHEAD);
+            throw new CloseRequestException(msg, ServerCnxn.DisconnectReason.NOT_READ_ONLY_CLIENT);
         }
         if (connReq.getLastZxidSeen() > zkDb.dataTree.lastProcessedZxid) {
             String msg = "Refusing session request for client "
@@ -1406,7 +1406,7 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
                          + " client must try another server";
 
             LOG.info(msg);
-            throw new CloseRequestException(msg, ServerCnxn.DisconnectReason.NOT_READ_ONLY_CLIENT);
+            throw new CloseRequestException(msg, ServerCnxn.DisconnectReason.CLIENT_ZXID_AHEAD);
         }
         int sessionTimeout = connReq.getTimeOut();
         byte[] passwd = connReq.getPasswd();

zookeeper-server/src/test/java/org/apache/zookeeper/server/ZooKeeperServerTest.java

@@ -20,12 +20,16 @@ package org.apache.zookeeper.server;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
 import java.io.File;
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.List;
 import org.apache.zookeeper.ZKTestCase;
 import org.apache.zookeeper.server.persistence.FileTxnLog;
+import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
 import org.apache.zookeeper.server.persistence.SnapStream;
 import org.apache.zookeeper.server.persistence.Util;
 import org.apache.zookeeper.test.ClientBase;
@@ -135,4 +139,29 @@ public class ZooKeeperServerTest extends ZKTestCase {
         }
     }
 
+    @Test
+    public void testClientZxidAhead() {
+        ZooKeeperServer zooKeeperServer = new ZooKeeperServer();
+        final ZKDatabase zkDatabase = new ZKDatabase(mock(FileTxnSnapLog.class));
+        zooKeeperServer.setZKDatabase(zkDatabase);
+
+        final ByteBuffer output = ByteBuffer.allocate(30);
+        // serialize a connReq
+        output.putInt(1);
+        // lastZxid
+        output.putLong(99L);
+        output.putInt(500);
+        output.putLong(123L);
+        output.putInt(1);
+        output.put((byte) 1);
+        output.put((byte) 1);
+        output.flip();
+
+        ServerCnxn.CloseRequestException e = assertThrows(ServerCnxn.CloseRequestException.class, () -> {
+            final NIOServerCnxn nioServerCnxn = mock(NIOServerCnxn.class);
+            zooKeeperServer.processConnectRequest(nioServerCnxn, output);
+        });
+        assertEquals(e.getReason(), ServerCnxn.DisconnectReason.CLIENT_ZXID_AHEAD);
+    }
+
 }

zookeeper-server/src/test/java/org/apache/zookeeper/server/quorum/ReadOnlyZooKeeperServerTest.java

@@ -0,0 +1,65 @@
+/*
+ * 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 org.apache.zookeeper.server.quorum;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.mock;
+import java.nio.ByteBuffer;
+import org.apache.zookeeper.server.NIOServerCnxn;
+import org.apache.zookeeper.server.ServerCnxn;
+import org.apache.zookeeper.server.ZKDatabase;
+import org.apache.zookeeper.server.ZooKeeperServer;
+import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
+import org.junit.jupiter.api.Test;
+
+/**
+ * test ReadOnlyZooKeeperServer
+ */
+public class ReadOnlyZooKeeperServerTest {
+
+    /**
+     * test method {@link ZooKeeperServer#processConnectRequest(org.apache.zookeeper.server.ServerCnxn, java.nio.ByteBuffer)}
+     */
+    @Test
+    public void testReadOnlyZookeeperServer() {
+        ReadOnlyZooKeeperServer readOnlyZooKeeperServer = new ReadOnlyZooKeeperServer(
+                mock(FileTxnSnapLog.class), mock(QuorumPeer.class), mock(ZKDatabase.class));
+
+        final ByteBuffer output = ByteBuffer.allocate(30);
+        // serialize a connReq
+        output.putInt(1);
+        output.putLong(1L);
+        output.putInt(500);
+        output.putLong(123L);
+        output.putInt(1);
+        output.put((byte) 1);
+        // set readOnly false
+        output.put((byte) 0);
+        output.flip();
+
+        ServerCnxn.CloseRequestException e = assertThrows(ServerCnxn.CloseRequestException.class, () -> {
+            final NIOServerCnxn nioServerCnxn = mock(NIOServerCnxn.class);
+            readOnlyZooKeeperServer.processConnectRequest(nioServerCnxn, output);
+        });
+        assertEquals(e.getReason(), ServerCnxn.DisconnectReason.NOT_READ_ONLY_CLIENT);
+    }
+
+
+}