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From ctubbsii <>
Subject [GitHub] accumulo pull request #223: ACCUMULO-4409 Create AccumuloMonitorAppender
Date Wed, 01 Mar 2017 17:12:13 GMT
Github user ctubbsii commented on a diff in the pull request:
    --- Diff: server/monitor/src/main/java/org/apache/accumulo/monitor/util/
    @@ -0,0 +1,153 @@
    + * 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
    + *
    + *
    + *
    + * 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.accumulo.monitor.util;
    +import static java.nio.charset.StandardCharsets.UTF_8;
    +import java.util.concurrent.Executors;
    +import java.util.concurrent.ScheduledExecutorService;
    +import java.util.concurrent.TimeUnit;
    +import java.util.concurrent.atomic.AtomicBoolean;
    +import org.apache.accumulo.core.Constants;
    +import org.apache.accumulo.core.client.Instance;
    +import org.apache.accumulo.core.conf.Property;
    +import org.apache.accumulo.core.zookeeper.ZooUtil;
    +import org.apache.accumulo.fate.zookeeper.ZooCache;
    +import org.apache.accumulo.fate.zookeeper.ZooCacheFactory;
    +import org.apache.accumulo.server.client.HdfsZooInstance;
    +import org.apache.log4j.AsyncAppender;
    +public class AccumuloMonitorAppender extends AsyncAppender {
    +  private final ScheduledExecutorService executorService;
    +  private final AtomicBoolean trackerScheduled;
    +  /**
    +   * A Log4j Appender which follows the registered location of the active Accumulo monitor
service, and forwards log messages to it
    +   */
    +  public AccumuloMonitorAppender() {
    +    // create the background thread to watch for updates to monitor location
    +    trackerScheduled = new AtomicBoolean(false);
    +    executorService = Executors.newSingleThreadScheduledExecutor(runnable -> {
    +      Thread t = new Thread(runnable, AccumuloMonitorAppender.class.getSimpleName() +
" Location Tracker");
    +      t.setDaemon(true);
    +      return t;
    --- End diff --
    Yes, we have a Daemon subclass of Thread, which is a trivial wrapper. I didn't feel the
need to use it because I think it's better that developers can read this code without any
knowledge or understanding of the behavior of some custom class.
    I'd probably favor deleting our Daemon class. I'm skeptical that it's all that useful.

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