HBASE-16061 Allow logging to a buffered console

conf/log4j.properties

@@ -80,13 +80,16 @@ log4j.appender.NullAppender=org.apache.log4j.varia.NullAppender
 
 #
 # console
-# Add "console" to rootlogger above if you want to use this 
+# Add "console" to rootlogger above if you want to use this
 #
 log4j.appender.console=org.apache.log4j.ConsoleAppender
 log4j.appender.console.target=System.err
 log4j.appender.console.layout=org.apache.log4j.PatternLayout
 log4j.appender.console.layout.ConversionPattern=%d{ISO8601} %-5p [%t] %c{2}: %m%n
 
+log4j.appender.asyncconsole=org.apache.hadoop.hbase.AsyncConsoleAppender
+log4j.appender.asyncconsole.target=System.err
+
 # Custom Logging levels
 
 log4j.logger.org.apache.zookeeper=INFO

hbase-common/src/main/java/org/apache/hadoop/hbase/AsyncConsoleAppender.java

@@ -0,0 +1,48 @@
+/**
+ * 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.hadoop.hbase;
+
+import org.apache.hadoop.hbase.classification.InterfaceAudience;
+import org.apache.log4j.AsyncAppender;
+import org.apache.log4j.ConsoleAppender;
+import org.apache.log4j.PatternLayout;
+
+/**
+ * Logger class that buffers before trying to log to the specified console.
+ */
+@InterfaceAudience.Private
+public class AsyncConsoleAppender extends AsyncAppender {
+  private final ConsoleAppender consoleAppender;
+
+  public AsyncConsoleAppender() {
+    super();
+    consoleAppender = new ConsoleAppender(new PatternLayout(
+        "%d{ISO8601} %-5p [%t] %c{2}: %m%n"));
+    this.addAppender(consoleAppender);
+  }
+
+  public void setTarget(String value) {
+    consoleAppender.setTarget(value);
+  }
+
+  public void activateOptions() {
+    consoleAppender.activateOptions();
+    super.activateOptions();
+  }
+
+}