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19 package org.apache.hadoop.metrics2.impl;
20
21 import org.apache.commons.logging.Log;
22 import org.apache.commons.logging.LogFactory;
23 import org.apache.hadoop.metrics2.MetricsExecutor;
24 import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
25 import org.apache.hadoop.metrics2.lib.MetricsExecutorImpl;
26
27
28 import java.util.concurrent.ScheduledFuture;
29 import java.util.concurrent.TimeUnit;
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39 @edu.umd.cs.findbugs.annotations.SuppressWarnings(
40 value="LI_LAZY_INIT_STATIC",
41 justification="Yeah, its weird but its what we want")
42 public class JmxCacheBuster {
43 private static final Log LOG = LogFactory.getLog(JmxCacheBuster.class);
44 private static Object lock = new Object();
45 private static ScheduledFuture fut = null;
46 private static MetricsExecutor executor = new MetricsExecutorImpl();
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51 public static void clearJmxCache() {
52
53
54 if (fut == null || (!fut.isDone() && fut.getDelay(TimeUnit.MILLISECONDS) > 100)) return;
55
56 synchronized (lock) {
57 fut = executor.getExecutor().schedule(new JmxCacheBusterRunnable(), 5, TimeUnit.SECONDS);
58 }
59 }
60
61 static class JmxCacheBusterRunnable implements Runnable {
62
63 @Override
64 public void run() {
65 LOG.trace("Clearing JMX mbean cache.");
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68
69
70 try {
71 DefaultMetricsSystem.INSTANCE.stop();
72 DefaultMetricsSystem.INSTANCE.start();
73 } catch (Exception exception ) {
74 LOG.debug("error clearing the jmx it appears the metrics system hasn't been started", exception);
75 }
76 }
77 }
78 }