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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.service;
import java.lang.management.GarbageCollectorMXBean;
import java.lang.management.ManagementFactory;
import java.lang.management.MemoryUsage;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import javax.management.MBeanServer;
import javax.management.Notification;
import javax.management.NotificationListener;
import javax.management.ObjectName;
import javax.management.openmbean.CompositeData;
import com.sun.management.GarbageCollectionNotificationInfo;
import com.sun.management.GcInfo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.lifecycle.LifecycleTransaction;
import org.apache.cassandra.utils.StatusLogger;
public class GCInspector implements NotificationListener, GCInspectorMXBean
{
public static final String MBEAN_NAME = "org.apache.cassandra.service:type=GCInspector";
private static final Logger logger = LoggerFactory.getLogger(GCInspector.class);
final static long MIN_LOG_DURATION = DatabaseDescriptor.getGCLogThreshold();
final static long GC_WARN_THRESHOLD_IN_MS = DatabaseDescriptor.getGCWarnThreshold();
final static long STAT_THRESHOLD = GC_WARN_THRESHOLD_IN_MS != 0 ? GC_WARN_THRESHOLD_IN_MS : MIN_LOG_DURATION;
/*
* The field from java.nio.Bits that tracks the total number of allocated
* bytes of direct memory requires via ByteBuffer.allocateDirect that have not been GCed.
*/
final static Field BITS_TOTAL_CAPACITY;
static
{
Field temp = null;
try
{
Class bitsClass = Class.forName("java.nio.Bits");
Field f = bitsClass.getDeclaredField("totalCapacity");
f.setAccessible(true);
temp = f;
}
catch (Throwable t)
{
logger.debug("Error accessing field of java.nio.Bits", t);
//Don't care, will just return the dummy value -1 if we can't get at the field in this JVM
}
BITS_TOTAL_CAPACITY = temp;
}
static final class State
{
final double maxRealTimeElapsed;
final double totalRealTimeElapsed;
final double sumSquaresRealTimeElapsed;
final double totalBytesReclaimed;
final double count;
final long startNanos;
State(double extraElapsed, double extraBytes, State prev)
{
this.totalRealTimeElapsed = prev.totalRealTimeElapsed + extraElapsed;
this.totalBytesReclaimed = prev.totalBytesReclaimed + extraBytes;
this.sumSquaresRealTimeElapsed = prev.sumSquaresRealTimeElapsed + (extraElapsed * extraElapsed);
this.startNanos = prev.startNanos;
this.count = prev.count + 1;
this.maxRealTimeElapsed = Math.max(prev.maxRealTimeElapsed, extraElapsed);
}
State()
{
count = maxRealTimeElapsed = sumSquaresRealTimeElapsed = totalRealTimeElapsed = totalBytesReclaimed = 0;
startNanos = System.nanoTime();
}
}
static final class GCState
{
final GarbageCollectorMXBean gcBean;
final boolean assumeGCIsPartiallyConcurrent;
final boolean assumeGCIsOldGen;
private String[] keys;
long lastGcTotalDuration = 0;
GCState(GarbageCollectorMXBean gcBean, boolean assumeGCIsPartiallyConcurrent, boolean assumeGCIsOldGen)
{
this.gcBean = gcBean;
this.assumeGCIsPartiallyConcurrent = assumeGCIsPartiallyConcurrent;
this.assumeGCIsOldGen = assumeGCIsOldGen;
}
String[] keys(GarbageCollectionNotificationInfo info)
{
if (keys != null)
return keys;
keys = info.getGcInfo().getMemoryUsageBeforeGc().keySet().toArray(new String[0]);
Arrays.sort(keys);
return keys;
}
}
final AtomicReference state = new AtomicReference<>(new State());
final Map gcStates = new HashMap<>();
public GCInspector()
{
MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
try
{
ObjectName gcName = new ObjectName(ManagementFactory.GARBAGE_COLLECTOR_MXBEAN_DOMAIN_TYPE + ",*");
for (ObjectName name : mbs.queryNames(gcName, null))
{
GarbageCollectorMXBean gc = ManagementFactory.newPlatformMXBeanProxy(mbs, name.getCanonicalName(), GarbageCollectorMXBean.class);
gcStates.put(gc.getName(), new GCState(gc, assumeGCIsPartiallyConcurrent(gc), assumeGCIsOldGen(gc)));
}
mbs.registerMBean(this, new ObjectName(MBEAN_NAME));
}
catch (Exception e)
{
throw new RuntimeException(e);
}
}
public static void register() throws Exception
{
GCInspector inspector = new GCInspector();
MBeanServer server = ManagementFactory.getPlatformMBeanServer();
ObjectName gcName = new ObjectName(ManagementFactory.GARBAGE_COLLECTOR_MXBEAN_DOMAIN_TYPE + ",*");
for (ObjectName name : server.queryNames(gcName, null))
{
server.addNotificationListener(name, inspector, null, null);
}
}
/*
* Assume that a GC type is at least partially concurrent and so a side channel method
* should be used to calculate application stopped time due to the GC.
*
* If the GC isn't recognized then assume that is concurrent and we need to do our own calculation
* via the the side channel.
*/
private static boolean assumeGCIsPartiallyConcurrent(GarbageCollectorMXBean gc)
{
switch (gc.getName())
{
//First two are from the serial collector
case "Copy":
case "MarkSweepCompact":
//Parallel collector
case "PS MarkSweep":
case "PS Scavenge":
case "G1 Young Generation":
//CMS young generation collector
case "ParNew":
return false;
case "ConcurrentMarkSweep":
case "G1 Old Generation":
return true;
default:
//Assume possibly concurrent if unsure
return true;
}
}
/*
* Assume that a GC type is an old generation collection so TransactionLogs.rescheduleFailedTasks()
* should be invoked.
*
* Defaults to not invoking TransactionLogs.rescheduleFailedTasks() on unrecognized GC names
*/
private static boolean assumeGCIsOldGen(GarbageCollectorMXBean gc)
{
switch (gc.getName())
{
case "Copy":
case "PS Scavenge":
case "G1 Young Generation":
case "ParNew":
return false;
case "MarkSweepCompact":
case "PS MarkSweep":
case "ConcurrentMarkSweep":
case "G1 Old Generation":
return true;
default:
//Assume not old gen otherwise, don't call
//TransactionLogs.rescheduleFailedTasks()
return false;
}
}
public void handleNotification(final Notification notification, final Object handback)
{
String type = notification.getType();
if (type.equals(GarbageCollectionNotificationInfo.GARBAGE_COLLECTION_NOTIFICATION))
{
// retrieve the garbage collection notification information
CompositeData cd = (CompositeData) notification.getUserData();
GarbageCollectionNotificationInfo info = GarbageCollectionNotificationInfo.from(cd);
String gcName = info.getGcName();
GcInfo gcInfo = info.getGcInfo();
long duration = gcInfo.getDuration();
/*
* The duration supplied in the notification info includes more than just
* application stopped time for concurrent GCs. Try and do a better job coming up with a good stopped time
* value by asking for and tracking cumulative time spent blocked in GC.
*/
GCState gcState = gcStates.get(gcName);
if (gcState.assumeGCIsPartiallyConcurrent)
{
long previousTotal = gcState.lastGcTotalDuration;
long total = gcState.gcBean.getCollectionTime();
gcState.lastGcTotalDuration = total;
duration = total - previousTotal; // may be zero for a really fast collection
}
StringBuilder sb = new StringBuilder();
sb.append(info.getGcName()).append(" GC in ").append(duration).append("ms. ");
long bytes = 0;
Map beforeMemoryUsage = gcInfo.getMemoryUsageBeforeGc();
Map afterMemoryUsage = gcInfo.getMemoryUsageAfterGc();
for (String key : gcState.keys(info))
{
MemoryUsage before = beforeMemoryUsage.get(key);
MemoryUsage after = afterMemoryUsage.get(key);
if (after != null && after.getUsed() != before.getUsed())
{
sb.append(key).append(": ").append(before.getUsed());
sb.append(" -> ");
sb.append(after.getUsed());
if (!key.equals(gcState.keys[gcState.keys.length - 1]))
sb.append("; ");
bytes += before.getUsed() - after.getUsed();
}
}
while (true)
{
State prev = state.get();
if (state.compareAndSet(prev, new State(duration, bytes, prev)))
break;
}
String st = sb.toString();
if (GC_WARN_THRESHOLD_IN_MS != 0 && duration > GC_WARN_THRESHOLD_IN_MS)
logger.warn(st);
else if (duration > MIN_LOG_DURATION)
logger.info(st);
else if (logger.isTraceEnabled())
logger.trace(st);
if (duration > STAT_THRESHOLD)
StatusLogger.log();
// if we just finished an old gen collection and we're still using a lot of memory, try to reduce the pressure
if (gcState.assumeGCIsOldGen)
LifecycleTransaction.rescheduleFailedDeletions();
}
}
public State getTotalSinceLastCheck()
{
return state.getAndSet(new State());
}
public double[] getAndResetStats()
{
State state = getTotalSinceLastCheck();
double[] r = new double[7];
r[0] = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - state.startNanos);
r[1] = state.maxRealTimeElapsed;
r[2] = state.totalRealTimeElapsed;
r[3] = state.sumSquaresRealTimeElapsed;
r[4] = state.totalBytesReclaimed;
r[5] = state.count;
r[6] = getAllocatedDirectMemory();
return r;
}
private static long getAllocatedDirectMemory()
{
if (BITS_TOTAL_CAPACITY == null) return -1;
try
{
return BITS_TOTAL_CAPACITY.getLong(null);
}
catch (Throwable t)
{
logger.trace("Error accessing field of java.nio.Bits", t);
//Don't care how or why we failed to get the value in this JVM. Return -1 to indicate failure
return -1;
}
}
}