[server] Disable shutdown hook for log4j to ensure Fluss log in shutdown hook can be collected (#2020)

* [server] Disable shutdown hook for log4j to ensure Fluss log in shutdown hook can be collected

* fix comments

Author: LiebingYu

fluss-dist/src/main/resources/bin/fluss-daemon.sh

@@ -79,7 +79,7 @@ FLUSS_LOG_PREFIX="${FLUSS_LOG_DIR}/fluss-${FLUSS_IDENT_STRING}-${DAEMON}-${id}-$
 log="${FLUSS_LOG_PREFIX}.log"
 out="${FLUSS_LOG_PREFIX}.out"
 
-log_setting=("-Dlog.file=${log}" "-Dlog4j.configuration=file:${FLUSS_CONF_DIR}/log4j.properties" "-Dlog4j.configurationFile=file:${FLUSS_CONF_DIR}/log4j.properties" "-Dlogback.configurationFile=file:${FLUSS_CONF_DIR}/logback.xml")
+log_setting=("-Dlog.file=${log}" "-Dlog4j.shutdownHookEnabled=false" "-Dlog4j.configuration=file:${FLUSS_CONF_DIR}/log4j.properties" "-Dlog4j.configurationFile=file:${FLUSS_CONF_DIR}/log4j.properties" "-Dlogback.configurationFile=file:${FLUSS_CONF_DIR}/logback.xml")
 
 function guaranteed_kill {
   to_stop_pid=$1

fluss-server/src/main/java/org/apache/fluss/server/ServerBase.java

@@ -49,6 +49,8 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 
+import static org.apache.fluss.server.utils.LogShutdownUtil.shutdownLogIfPossible;
+
 /** An abstract base server class for {@link CoordinatorServer} & {@link TabletServer}. */
 public abstract class ServerBase implements AutoCloseableAsync, FatalErrorHandler {
 
@@ -146,7 +148,12 @@ public void start() throws Exception {
     private void addShutDownHook() {
         shutDownHook =
                 ShutdownHookUtil.addShutdownHook(
-                        () -> this.closeAsync(Result.JVM_SHUTDOWN).join(), getServerName(), LOG);
+                        () -> {
+                            this.closeAsync(Result.JVM_SHUTDOWN).join();
+                            shutdownLogIfPossible();
+                        },
+                        getServerName(),
+                        LOG);
     }
 
     @Override

fluss-server/src/main/java/org/apache/fluss/server/utils/LogShutdownUtil.java

@@ -0,0 +1,42 @@
+/*
+ * 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.fluss.server.utils;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/** Utility class to shut down log system. */
+public class LogShutdownUtil {
+
+    private static final Logger LOG = LoggerFactory.getLogger(LogShutdownUtil.class);
+
+    public static void shutdownLogIfPossible() {
+        // To avoid binding to a specific logging implementation, we use reflection here.
+        try {
+            // To ensure that logs within the JVM shutdown hook can be printed when using Log4j2,
+            // Fluss has disabled Log4j2's shutdown hook; therefore, manual shutdown is required
+            // here.
+            Class<?> logManager = Class.forName("org.apache.logging.log4j.LogManager");
+            logManager.getMethod("shutdown").invoke(null);
+        } catch (ClassNotFoundException e) {
+            LOG.error("Class org.apache.logging.log4j.LogManager not found", e);
+        } catch (Exception e) {
+            LOG.error("Error to invoke shutdown method of org.apache.logging.log4j.LogManager", e);
+        }
+    }
+}