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com.jn.langx.util.memory.leak.ResourceLeakDetector Maven / Gradle / Ivy
Java lang extensions for java6+, a supplement to , replacement of a Guava, commons-lang.
Core utilities, Collection utilities, IO utilities, Cache, Configuration library ...
package com.jn.langx.util.memory.leak;
import com.jn.langx.util.Emptys;
import com.jn.langx.util.Preconditions;
import com.jn.langx.util.SystemPropertys;
import com.jn.langx.text.properties.PropertiesAccessor;
import com.jn.langx.util.random.ThreadLocalRandom;
import com.jn.langx.util.reflect.Reflects;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import static com.jn.langx.util.SystemPropertys.NEWLINE;
public class ResourceLeakDetector {
private static String RESOURCE_LEAK_DETECTION_PREFIX = SystemPropertys.getAccessor().getString("RESOURCE_LEAK_DETECTION_PREFIX", "langx.leakDetection");
private static final String PROP_LEVEL = RESOURCE_LEAK_DETECTION_PREFIX + ".level";
private static final Level DEFAULT_LEVEL = Level.SIMPLE;
private static final String PROP_TARGET_RECORDS = RESOURCE_LEAK_DETECTION_PREFIX + ".targetRecords";
private static final int DEFAULT_TARGET_RECORDS = 4;
private static final String PROP_SAMPLING_INTERVAL = RESOURCE_LEAK_DETECTION_PREFIX + ".samplingInterval";
// There is a minor performance benefit in TLR if this is a power of 2.
private static final int DEFAULT_SAMPLING_INTERVAL = 128;
private static final int TARGET_RECORDS;
static final int SAMPLING_INTERVAL;
/**
* Represents the level of resource leak detection.
*/
public enum Level {
/**
* Disables resource leak detection.
*/
DISABLED,
/**
* Enables simplistic sampling resource leak detection which reports there is a leak or not,
* at the cost of small overhead (default).
*/
SIMPLE,
/**
* Enables advanced sampling resource leak detection which reports where the leaked object was accessed
* recently at the cost of high overhead.
*/
ADVANCED,
/**
* Enables paranoid resource leak detection which reports where the leaked object was accessed recently,
* at the cost of the highest possible overhead (for testing purposes only).
*/
PARANOID;
/**
* Returns level based on string value. Accepts also string that represents ordinal number of enum.
*
* @param levelStr - level string : DISABLED, SIMPLE, ADVANCED, PARANOID. Ignores case.
* @return corresponding level or SIMPLE level in case of no match.
*/
static Level parseLevel(String levelStr) {
String trimmedLevelStr = levelStr.trim();
for (Level l : values()) {
if (trimmedLevelStr.equalsIgnoreCase(l.name()) || trimmedLevelStr.equals(String.valueOf(l.ordinal()))) {
return l;
}
}
return DEFAULT_LEVEL;
}
}
private static Level level;
private static final Logger logger = LoggerFactory.getLogger(ResourceLeakDetector.class);
static {
final boolean disabled;
PropertiesAccessor systemPropertiesAccessor = SystemPropertys.getAccessor();
String enabledSwitch = RESOURCE_LEAK_DETECTION_PREFIX + ".enabled";
if (systemPropertiesAccessor.get(enabledSwitch) != null) {
disabled = systemPropertiesAccessor.getBoolean(enabledSwitch, false);
logger.debug("-{}: {}", enabledSwitch, disabled);
} else {
disabled = false;
}
Level defaultLevel = disabled ? Level.DISABLED : DEFAULT_LEVEL;
String levelStr = systemPropertiesAccessor.getString(PROP_LEVEL, defaultLevel.name());
Level level = Level.parseLevel(levelStr);
TARGET_RECORDS = systemPropertiesAccessor.getInteger(PROP_TARGET_RECORDS, DEFAULT_TARGET_RECORDS);
SAMPLING_INTERVAL = systemPropertiesAccessor.getInteger(PROP_SAMPLING_INTERVAL, DEFAULT_SAMPLING_INTERVAL);
ResourceLeakDetector.level = level;
if (logger.isDebugEnabled()) {
logger.debug("-D{}: {}", PROP_LEVEL, level.name().toLowerCase());
logger.debug("-D{}: {}", PROP_TARGET_RECORDS, TARGET_RECORDS);
}
}
/**
* Returns {@code true} if resource leak detection is enabled.
*/
public static boolean isEnabled() {
return getLevel().ordinal() > Level.DISABLED.ordinal();
}
/**
* Sets the resource leak detection level.
*/
public static void setLevel(Level level) {
Preconditions.checkNotNull(level);
ResourceLeakDetector.level = level;
}
/**
* Returns the current resource leak detection level.
*/
public static Level getLevel() {
return level;
}
/**
* the collection of active resources
*/
private final Set allLeaks = Collections.newSetFromMap(new ConcurrentHashMap());
private final ReferenceQueue refQueue = new ReferenceQueue();
private final ConcurrentMap reportedLeaks = new ConcurrentHashMap();
private final String resourceType;
private final int samplingInterval;
/**
* This should not be used directly by users of {@link ResourceLeakDetector}.
* Please use {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class)}
* or {@link ResourceLeakDetectorFactory#newResourceLeakDetector(Class, int)}
*/
public ResourceLeakDetector(Class resourceType, int samplingInterval) {
this.resourceType = Reflects.getSimpleClassName(resourceType);
this.samplingInterval = samplingInterval;
}
/**
* Creates a new {@link ResourceLeakTracker} which is expected to be closed via
* {@link ResourceLeakTracker#close(Object)} when the related resource is deallocated.
*
* @return the {@link ResourceLeakTracker} or {@code null}
*/
@SuppressWarnings("unchecked")
public final ResourceLeakTracker track(T obj) {
return track0(obj);
}
@SuppressWarnings("unchecked")
private DefaultResourceLeak track0(T obj) {
Level level = ResourceLeakDetector.level;
if (level == Level.DISABLED) {
return null;
}
if (level.ordinal() < Level.PARANOID.ordinal()) {
if ((ThreadLocalRandom.current().nextInt(samplingInterval)) == 0) {
reportLeak();
return new DefaultResourceLeak(obj, refQueue, allLeaks);
}
return null;
}
reportLeak();
return new DefaultResourceLeak(obj, refQueue, allLeaks);
}
private void clearRefQueue() {
for (; ; ) {
@SuppressWarnings("unchecked")
DefaultResourceLeak ref = (DefaultResourceLeak) refQueue.poll();
if (ref == null) {
break;
}
ref.dispose();
}
}
private void reportLeak() {
if (!logger.isErrorEnabled()) {
clearRefQueue();
return;
}
// Detect and report previous leaks.
for (; ; ) {
DefaultResourceLeak ref = (DefaultResourceLeak) refQueue.poll();
if (ref == null) {
break;
}
if (!ref.dispose()) {
continue;
}
String records = ref.toString();
if (reportedLeaks.putIfAbsent(records, Boolean.TRUE) == null) {
if (records.isEmpty()) {
reportUntracedLeak(resourceType);
} else {
reportTracedLeak(resourceType, records);
}
}
}
}
/**
* This method is called when a traced leak is detected. It can be overridden for tracking how many times leaks
* have been detected.
*/
protected void reportTracedLeak(String resourceType, String records) {
logger.error(
"LEAK: {} was not (close | stop | release | dispose, or other similar method) before it's garbage-collected. " +
"See https://netty.io/wiki/reference-counted-objects.html for more information.{}",
resourceType, records);
}
/**
* This method is called when an untraced leak is detected. It can be overridden for tracking how many times leaks
* have been detected.
*/
protected void reportUntracedLeak(String resourceType) {
logger.error("LEAK: {} was not (close | stop | release | dispose, or other similar method) before it's garbage-collected. " +
"Enable advanced leak reporting to find out where the leak occurred. " +
"To enable advanced leak reporting, " +
"specify the JVM option '-D{}={}' or call {}.setLevel() " +
"See https://netty.io/wiki/reference-counted-objects.html for more information.",
resourceType, PROP_LEVEL, Level.ADVANCED.name().toLowerCase(), Reflects.getSimpleClassName(this));
}
@SuppressWarnings({"deprecation","unused"})
private static final class DefaultResourceLeak extends WeakReference implements ResourceLeakTracker {
/**
* generics and updaters do not mix.
*/
private static final AtomicReferenceFieldUpdater headUpdater = AtomicReferenceFieldUpdater.newUpdater(DefaultResourceLeak.class, Record.class, "head");
/**
* generics and updaters do not mix.
*/
private static final AtomicIntegerFieldUpdater droppedRecordsUpdater = AtomicIntegerFieldUpdater.newUpdater(DefaultResourceLeak.class, "droppedRecords");
private volatile Record head;
private volatile int droppedRecords;
private final Set allLeaks;
private final int trackedHash;
DefaultResourceLeak(Object referent, ReferenceQueue refQueue, Set allLeaks) {
super(referent, refQueue);
assert referent != null;
// Store the hash of the tracked object to later assert it in the close(...) method.
// It's important that we not store a reference to the referent as this would disallow it from
// be collected via the WeakReference.
trackedHash = System.identityHashCode(referent);
Preconditions.checkNotNull(allLeaks);
allLeaks.add(this);
// Create a new Record so we always have the creation stacktrace included.
headUpdater.set(this, new ResourceLeakDetector.Record(ResourceLeakDetector.Record.BOTTOM));
this.allLeaks = allLeaks;
}
@Override
public void record() {
record0(null);
}
@Override
public void record(Object hint) {
record0(hint);
}
/**
* This method works by exponentially backing off as more records are present in the stack. Each record has a
* 1 / 2^n chance of dropping the top most record and replacing it with itself. This has a number of convenient
* properties:
*
*
* The current record is always recorded. This is due to the compare and swap dropping the top most
* record, rather than the to-be-pushed record.
* The very last access will always be recorded. This comes as a property of 1.
* It is possible to retain more records than the target, based upon the probability distribution.
* It is easy to keep a precise record of the number of elements in the stack, since each element has to
* know how tall the stack is.
*
*
* In this particular implementation, there are also some advantages. A thread local random is used to decide
* if something should be recorded. This means that if there is a deterministic access pattern, it is now
* possible to see what other accesses occur, rather than always dropping them. Second, after
* {@link #TARGET_RECORDS} accesses, backoff occurs. This matches typical access patterns,
* where there are either a high number of accesses (i.e. a cached buffer), or low (an ephemeral buffer), but
* not many in between.
*
* The use of atomics avoids serializing a high number of accesses, when most of the records will be thrown
* away. High contention only happens when there are very few existing records, which is only likely when the
* object isn't shared! If this is a problem, the loop can be aborted and the record dropped, because another
* thread won the race.
*/
private void record0(Object hint) {
// Check TARGET_RECORDS > 0 here to avoid similar check before remove from and add to lastRecords
if (TARGET_RECORDS > 0) {
ResourceLeakDetector.Record oldHead;
ResourceLeakDetector.Record prevHead;
ResourceLeakDetector.Record newHead;
boolean dropped;
do {
if ((prevHead = oldHead = headUpdater.get(this)) == null) {
// already closed.
return;
}
final int numElements = oldHead.pos + 1;
if (numElements >= TARGET_RECORDS) {
final int backOffFactor = Math.min(numElements - TARGET_RECORDS, 30);
if (dropped = ThreadLocalRandom.current().nextInt(1 << backOffFactor) != 0) {
prevHead = oldHead.next;
}
} else {
dropped = false;
}
newHead = hint != null ? new ResourceLeakDetector.Record(prevHead, hint) : new ResourceLeakDetector.Record(prevHead);
} while (!headUpdater.compareAndSet(this, oldHead, newHead));
if (dropped) {
droppedRecordsUpdater.incrementAndGet(this);
}
}
}
boolean dispose() {
clear();
return allLeaks.remove(this);
}
public boolean close() {
if (allLeaks.remove(this)) {
// Call clear so the reference is not even enqueued.
clear();
headUpdater.set(this, null);
return true;
}
return false;
}
@Override
public boolean close(T trackedObject) {
// Ensure that the object that was tracked is the same as the one that was passed to close(...).
assert trackedHash == System.identityHashCode(trackedObject);
try {
return close();
} finally {
// This method will do `synchronized(trackedObject)` and we should be sure this will not cause deadlock.
// It should not, because somewhere up the callstack should be a (successful) `trackedObject.release`,
// therefore it is unreasonable that anyone else, anywhere, is holding a lock on the trackedObject.
// (Unreasonable but possible, unfortunately.)
reachabilityFence0(trackedObject);
}
}
/**
* Ensures that the object referenced by the given reference remains
* strongly reachable
*
Recent versions of the JDK have a nasty habit of prematurely deciding objects are unreachable.
* see: https://stackoverflow.com/questions/26642153/finalize-called-on-strongly-reachable-object-in-java-8
* The Java 9 method Reference.reachabilityFence offers a solution to this problem.
*
*
This method is always implemented as a synchronization on {@code ref}, not as
* {@code Reference.reachabilityFence} for consistency across platforms and to allow building on JDK 6-8.
* It is the caller's responsibility to ensure that this synchronization will not cause deadlock.
*
* @param ref the reference. If {@code null}, this method has no effect.
*/
private static void reachabilityFence0(Object ref) {
if (ref != null) {
//synchronized (ref) {
// Empty synchronized is ok: https://stackoverflow.com/a/31933260/1151521
//}
}
}
@Override
public String toString() {
Record oldHead = headUpdater.getAndSet(this, null);
if (oldHead == null) {
// Already closed
return "";
}
final int dropped = droppedRecordsUpdater.get(this);
int duped = 0;
int present = oldHead.pos + 1;
// Guess about 2 kilobytes per stack trace
StringBuilder buf = new StringBuilder(present * 2048).append(NEWLINE);
buf.append("Recent access records: ").append(NEWLINE);
int i = 1;
Set seen = new HashSet(present);
for (; oldHead != Record.BOTTOM; oldHead = oldHead.next) {
String s = oldHead.toString();
if (seen.add(s)) {
if (oldHead.next == Record.BOTTOM) {
buf.append("Created at:").append(NEWLINE).append(s);
} else {
buf.append('#').append(i++).append(':').append(NEWLINE).append(s);
}
} else {
duped++;
}
}
if (duped > 0) {
buf.append(": ")
.append(duped)
.append(" leak records were discarded because they were duplicates")
.append(NEWLINE);
}
if (dropped > 0) {
buf.append(": ")
.append(dropped)
.append(" leak records were discarded because the leak record count is targeted to ")
.append(TARGET_RECORDS)
.append(". Use system property ")
.append(PROP_TARGET_RECORDS)
.append(" to increase the limit.")
.append(NEWLINE);
}
buf.setLength(buf.length() - NEWLINE.length());
return buf.toString();
}
}
private static final AtomicReference excludedMethods =
new AtomicReference(Emptys.EMPTY_STRINGS);
public static void addExclusions(Class clz, String... methodNames) {
Set nameSet = new HashSet(Arrays.asList(methodNames));
// Use loop rather than lookup. This avoids knowing the parameters, and doesn't have to handle
// NoSuchMethodException.
for (Method method : clz.getDeclaredMethods()) {
if (nameSet.remove(method.getName()) && nameSet.isEmpty()) {
break;
}
}
if (!nameSet.isEmpty()) {
throw new IllegalArgumentException("Can't find '" + nameSet + "' in " + clz.getName());
}
String[] oldMethods;
String[] newMethods;
do {
oldMethods = excludedMethods.get();
newMethods = Arrays.copyOf(oldMethods, oldMethods.length + 2 * methodNames.length);
for (int i = 0; i < methodNames.length; i++) {
newMethods[oldMethods.length + i * 2] = clz.getName();
newMethods[oldMethods.length + i * 2 + 1] = methodNames[i];
}
} while (!excludedMethods.compareAndSet(oldMethods, newMethods));
}
private static final class Record extends Throwable {
private static final long serialVersionUID = 6065153674892850720L;
private static final ResourceLeakDetector.Record BOTTOM = new ResourceLeakDetector.Record();
private final String hintString;
private final ResourceLeakDetector.Record next;
private final int pos;
Record(Record next, Object hint) {
// This needs to be generated even if toString() is never called as it may change later on.
hintString = hint instanceof ResourceLeakHint ? ((ResourceLeakHint) hint).toHintString() : hint.toString();
this.next = next;
this.pos = next.pos + 1;
}
Record(Record next) {
hintString = null;
this.next = next;
this.pos = next.pos + 1;
}
// Used to terminate the stack
private Record() {
hintString = null;
next = null;
pos = -1;
}
@Override
public String toString() {
StringBuilder buf = new StringBuilder(2048);
if (hintString != null) {
buf.append("\tHint: ").append(hintString).append(NEWLINE);
}
// Append the stack trace.
StackTraceElement[] array = getStackTrace();
// Skip the first three elements.
out:
for (int i = 3; i < array.length; i++) {
StackTraceElement element = array[i];
// Strip the noisy stack trace elements.
String[] exclusions = excludedMethods.get();
for (int k = 0; k < exclusions.length; k += 2) {
if (exclusions[k].equals(element.getClassName())
&& exclusions[k + 1].equals(element.getMethodName())) {
continue out;
}
}
buf.append('\t');
buf.append(element.toString());
buf.append(NEWLINE);
}
return buf.toString();
}
}
}
