Github user sounakr commented on a diff in the pull request:
https://github.com/apache/carbondata/pull/1662#discussion_r157335368
--- Diff:
core/src/main/java/org/apache/carbondata/core/dictionary/server/NonSecureDictionaryServer.java
---
@@ -0,0 +1,180 @@
+/*
+ * 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.carbondata.core.dictionary.server;
+
+import java.net.InetSocketAddress;
+
+import org.apache.carbondata.common.logging.LogService;
+import org.apache.carbondata.common.logging.LogServiceFactory;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import
org.apache.carbondata.core.dictionary.generator.key.DictionaryMessage;
+import
org.apache.carbondata.core.dictionary.generator.key.DictionaryMessageType;
+import
org.apache.carbondata.core.dictionary.service.AbstractDictionaryServer;
+import org.apache.carbondata.core.metadata.schema.table.CarbonTable;
+import org.apache.carbondata.core.util.CarbonProperties;
+
+
+import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.ChannelPipeline;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.channel.socket.nio.NioServerSocketChannel;
+import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
+
+/**
+ * Dictionary Server to generate dictionary keys.
+ */
+public class NonSecureDictionaryServer extends AbstractDictionaryServer
+ implements DictionaryServer {
+
+ private static final LogService LOGGER =
+
LogServiceFactory.getLogService(NonSecureDictionaryServer.class.getName());
+
+ private NonSecureDictionaryServerHandler
nonSecureDictionaryServerHandler;
+
+ private EventLoopGroup boss;
+ private EventLoopGroup worker;
+ private int port;
+ private String host;
+ private static Object lock = new Object();
+ private static NonSecureDictionaryServer INSTANCE = null;
+
+ private NonSecureDictionaryServer(int port) {
+ this.port = port;
+ startServer();
+ }
+
+ public static synchronized DictionaryServer getInstance(int port,
CarbonTable carbonTable)
+ throws Exception {
+ if (INSTANCE == null) {
+ INSTANCE = new NonSecureDictionaryServer(port);
+ }
+ INSTANCE.initializeDictionaryGenerator(carbonTable);
--- End diff --
Yes, Initially the code was like
if (INSTANCE == null) {
synchronized(lock) {
if (INSTANCE == null)
...
...
There was a dual check of INSTANCE for concurrency. The dual check will
cause a find bug error. In order to void this the method is turned into
synchronized method. Also initializeDictionaryGenerator will finally invoke
method like initializeGeneratorForTable which is also synchronized. So even
though we remove the method as synchronized the execution will never be
concurrent.
---
