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/*
* 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.brooklyn.util.javalang;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;
import org.apache.brooklyn.util.collections.MutableList;
import org.apache.brooklyn.util.text.Strings;
import com.google.common.annotations.Beta;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.RemovalListener;
import com.google.common.cache.RemovalNotification;
/**
* Tracks the amount of memory consumed by the given objects in use.
*
* In one tracker, {@link WeakReference}s are used internally, so that shortly after a {@link #track(Object, long)}ed object is GC'd,
* the {@link #getBytesUsed()} value decrements appropriately.
*
* In another we let clients listen for {@link SoftReference} expiration again using weak references.
*
* Both only work with clients who opt-in with calls to these methods/instances.
*
* This also includes a technique for clearing soft references.
* If you have access to a console you can force it with:
*
*
* org.apache.brooklyn.util.javalang.MemoryUsageTracker.forceClearSoftReferences()
*
*/
@Beta // made beta in 0.10.0 due to dodgy nature of it
public class MemoryUsageTracker {
/**
* Shared instance for use for tracking memory used by {@link SoftReference}.
*
* Callers should only use this field to {@link #track(Object, long)} objects which have (or will soon have)
* given up their strong references, so that only soft or weak references remain.
* Provided size estimates are accurate, {@link #getBytesUsed()} will report
* the amount of used memory which is reclaimable by collecting soft references.
*
* This is particularly handy for tracking {@link SoftReference}s, because otherwise you can quickly get to a state
* where {@link Runtime#freeMemory()} looks very low.
*
* Also consider {@link #forceClearSoftReferences()} to get useful information.
**/
public static final MemoryUsageTracker SOFT_REFERENCES = new MemoryUsageTracker();
AtomicLong bytesUsed = new AtomicLong(0);
Cache memoryTrackedReferences = CacheBuilder.newBuilder()
.weakKeys()
.removalListener(new RemovalListener() {
@Override
public void onRemoval(RemovalNotification notification) {
bytesUsed.addAndGet(-notification.getValue());
}
}).build();
public void track(Object instance, long bytesUsedByInstance) {
bytesUsed.addAndGet(bytesUsedByInstance);
memoryTrackedReferences.put(instance, bytesUsedByInstance);
}
public long getBytesUsed() {
memoryTrackedReferences.cleanUp();
return bytesUsed.get();
}
/** forces all soft references to be cleared by trying to allocate an enormous chunk of memory,
* returns a description of what was done
* (tune with {@link #forceClearSoftReferences(long, int)}
* for greater than 200M precision in the output message, if you really care about that) */
public static String forceClearSoftReferences() {
return forceClearSoftReferences(1000*1000, Integer.MAX_VALUE);
}
/** as {@link #forceClearSoftReferences()} but gives control over headroom and max chunk size.
* it tries to undershoot by headroom as it approaches maximum (and then overshoot)
* to minimize the chance we take exactly all the memory and starve another thread;
* and it uses the given max chunk size in cases where the caller wants more precision
* (the available memory will be fragmented so the smaller the chunks the more it can
* fill in, but at the expense of time and actual memory provisioned) */
public static String forceClearSoftReferences(long headroom, int maxChunk) {
final long HEADROOM = 1000*1000;
long lastAmount = 0;
long nextAmount = 0;
long oldUsed = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
try {
List dd = MutableList.of();
while (true) {
int size = (int)Math.min(Runtime.getRuntime().freeMemory()-HEADROOM, maxChunk);
if (size "+Strings.makeSizeString(newUsed)+" / "+
Strings.makeSizeString(Runtime.getRuntime().totalMemory());
}
/** Tracking for soft usage through SoftlyPresent instances */
public static class SoftUsageTracker {
private Cache> cache = null;
public synchronized void enable() {
cache = CacheBuilder.newBuilder().weakKeys().build();
}
public synchronized void disable() {
cache = null;
}
public synchronized long getTotalEntries() {
return cache==null ? -1 : cache.size();
}
public synchronized double getPercentagePresent() {
if (cache==null) return -1;
int present=0, total=0;
for (SoftReference sr: cache.asMap().values()) {
total++;
if (sr.get()!=null) present++;
}
if (total==0) return -1;
return 1.0*present / total;
}
public synchronized void track(Object key, SoftReference ref) {
if (cache!=null) cache.put(key, ref);
}
public synchronized void untrack(Object key) {
if (cache!=null) cache.invalidate(key);
}
}
}