Github user ctubbsii commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/223#discussion_r103738255
--- Diff:
server/monitor/src/main/java/org/apache/accumulo/monitor/util/AccumuloMonitorAppender.java
---
@@ -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
+ *
+ * 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.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;
+import org.apache.log4j.net.SocketAppender;
+import org.apache.zookeeper.data.Stat;
+
+import com.google.common.net.HostAndPort;
+
+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;
+ });
+ }
+
+ @Override
+ public void activateOptions() {
+ // only schedule it once (in case options get activated more than
once); not sure if this is possible
+ if (trackerScheduled.compareAndSet(false, true)) {
+ // wait 5 seconds, then run every 5 seconds
+ executorService.scheduleAtFixedRate(new MonitorTracker(), 5, 5,
TimeUnit.SECONDS);
+ }
+ super.activateOptions();
+ }
+
+ @Override
+ public void close() {
+ if (!executorService.isShutdown()) {
+ executorService.shutdownNow();
+ }
+ super.close();
+ }
+
+ private class MonitorTracker implements Runnable {
+
+ private String path;
+ private ZooCache zooCache;
+
+ private long lastModifiedTransactionId;
+ private SocketAppender lastSocketAppender;
+
+ public MonitorTracker() {
+
+ // path and zooCache are lazily set the first time this tracker is
run
+ // this allows the tracker to be constructed and scheduled during
log4j initialization without
+ // triggering any actual logs from the Accumulo or ZooKeeper code
+ this.path = null;
+ this.zooCache = null;
+
+ this.lastModifiedTransactionId = 0;
+ this.lastSocketAppender = null;
+ }
+
+ @Override
+ public void run() {
--- End diff --
Not yet. I did a lot of manual testing. I was thinking about how to test it
with a unit test, since Mike had explained why the previous MAC integration
test wasn't that useful. I think I have a good idea of what that would look
like, and will try to add it to the PR soon.
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