SOLR-8186: Added robustness to the dynamic log muting logic

solr/core/src/java/org/apache/solr/servlet/SolrDispatchFilter.java

@@ -37,7 +37,6 @@ import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Enumeration;
 import java.util.Locale;
 import java.util.Properties;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -49,14 +48,10 @@ import org.apache.commons.io.input.CloseShieldInputStream;
 import org.apache.commons.io.output.CloseShieldOutputStream;
 import org.apache.commons.lang.StringUtils;
 import org.apache.http.client.HttpClient;
-import org.apache.log4j.Appender;
-import org.apache.log4j.ConsoleAppender;
-import org.apache.log4j.LogManager;
 import org.apache.solr.common.SolrException;
 import org.apache.solr.common.SolrException.ErrorCode;
 import org.apache.solr.common.cloud.SolrZkClient;
 import org.apache.solr.common.util.ExecutorUtil;
-import org.apache.solr.common.util.SuppressForbidden;
 import org.apache.solr.core.CoreContainer;
 import org.apache.solr.core.NodeConfig;
 import org.apache.solr.core.SolrCore;
@@ -124,7 +119,7 @@ public class SolrDispatchFilter extends BaseSolrFilter {
   {
     String muteConsole = System.getProperty(SOLR_LOG_MUTECONSOLE);
     if (muteConsole != null && !Arrays.asList("false","0","off","no").contains(muteConsole.toLowerCase(Locale.ROOT))) {
-      muteConsole();
+      StartupLoggingUtils.muteConsole();
     }
     log.info("SolrDispatchFilter.init(): {}", this.getClass().getClassLoader());
 
@@ -161,18 +156,6 @@ public class SolrDispatchFilter extends BaseSolrFilter {
     log.info("SolrDispatchFilter.init() done");
   }
 
-  @SuppressForbidden(reason = "Legitimate log4j access")
-  private void muteConsole() {
-    Enumeration appenders = LogManager.getRootLogger().getAllAppenders();
-    while (appenders.hasMoreElements()) {
-      Appender appender = (Appender) appenders.nextElement();
-      if (appender instanceof ConsoleAppender) {
-        log.info("Property solr.log.muteconsole given. Muting ConsoleAppender named " + appender.getName());
-        LogManager.getRootLogger().removeAppender(appender);
-      }
-    }
-  }
-
   /**
    * Override this to change CoreContainer initialization
    * @return a CoreContainer to hold this server's cores

solr/core/src/java/org/apache/solr/servlet/StartupLoggingUtils.java

@@ -0,0 +1,85 @@
+/*
+ * 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.solr.servlet;
+
+import java.lang.invoke.MethodHandles;
+import java.util.Enumeration;
+
+import org.apache.log4j.Appender;
+import org.apache.log4j.ConsoleAppender;
+import org.apache.log4j.LogManager;
+import org.apache.solr.common.util.SuppressForbidden;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.slf4j.impl.StaticLoggerBinder;
+
+/**
+ * Handles dynamic modification of during startup, before CoreContainer is created
+ * <p>
+ *   WARNING: This class should only be used during startup. For modifying log levels etc
+ *   during runtime, SLF4J and LogWatcher must be used.
+ * </p>
+ */
+final class StartupLoggingUtils {
+  private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
+  private final static StaticLoggerBinder binder = StaticLoggerBinder.getSingleton();
+
+  /**
+   * Disables all log4j ConsoleAppender's by modifying log4j configuration dynamically.
+   * Must only be used during early startup
+   * @return true if ok or else false if something happened, e.g. log4j classes were not in classpath
+   */
+  @SuppressForbidden(reason = "Legitimate log4j access")
+  static boolean muteConsole() {
+    try {
+      if (!isLog4jActive()) {
+        logNotSupported("Could not mute logging to console.");
+        return false;
+      }
+      org.apache.log4j.Logger rootLogger = LogManager.getRootLogger();
+      Enumeration appenders = rootLogger.getAllAppenders();
+      while (appenders.hasMoreElements()) {
+        Appender appender = (Appender) appenders.nextElement();
+        if (appender instanceof ConsoleAppender) {
+          log.info("Property solr.log.muteconsole given. Muting ConsoleAppender named " + appender.getName());
+          rootLogger.removeAppender(appender);
+        }
+      }
+      return true;
+    } catch (Exception e) {
+      logNotSupported("Could not mute logging to console.");
+      return false;
+    }
+  }
+
+  private static boolean isLog4jActive() {
+    try {
+      // Make sure we have log4j LogManager in classpath
+      Class.forName("org.apache.log4j.LogManager");
+      // Make sure that log4j is really selected as logger in slf4j - we could have LogManager in the bridge class :)
+      return binder.getLoggerFactoryClassStr().contains("Log4jLoggerFactory");
+    } catch (Exception e) {
+      return false;
+    }
+  }
+
+  private static void logNotSupported(String msg) {
+    log.warn("{} Dynamic log manipulation currently only supported for Log4j. "
+        + "Please consult your logging framework of choice on how to configure the appropriate logging.", msg);
+  }
+}