Package io.netty.util
Class ResourceLeakDetector.DefaultResourceLeak<T>
- java.lang.Object
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- java.lang.ref.Reference<T>
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- java.lang.ref.WeakReference<java.lang.Object>
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- io.netty.util.ResourceLeakDetector.DefaultResourceLeak<T>
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- All Implemented Interfaces:
ResourceLeak,ResourceLeakTracker<T>
- Enclosing class:
- ResourceLeakDetector<T>
private static final class ResourceLeakDetector.DefaultResourceLeak<T> extends java.lang.ref.WeakReference<java.lang.Object> implements ResourceLeakTracker<T>, ResourceLeak
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Field Summary
Fields Modifier and Type Field Description private java.util.Set<ResourceLeakDetector.DefaultResourceLeak<?>>allLeaksprivate intdroppedRecordsprivate static java.util.concurrent.atomic.AtomicIntegerFieldUpdater<ResourceLeakDetector.DefaultResourceLeak<?>>droppedRecordsUpdaterprivate ResourceLeakDetector.Recordheadprivate static java.util.concurrent.atomic.AtomicReferenceFieldUpdater<ResourceLeakDetector.DefaultResourceLeak<?>,ResourceLeakDetector.Record>headUpdaterprivate inttrackedHash
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Constructor Summary
Constructors Constructor Description DefaultResourceLeak(java.lang.Object referent, java.lang.ref.ReferenceQueue<java.lang.Object> refQueue, java.util.Set<ResourceLeakDetector.DefaultResourceLeak<?>> allLeaks)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description booleanclose()Close the leak so thatResourceLeakDetectordoes not warn about leaked resources.booleanclose(T trackedObject)Close the leak so thatResourceLeakTrackerdoes not warn about leaked resources.(package private) booleandispose()private static voidreachabilityFence0(java.lang.Object ref)Ensures that the object referenced by the given reference remains strongly reachable, regardless of any prior actions of the program that might otherwise cause the object to become unreachable; thus, the referenced object is not reclaimable by garbage collection at least until after the invocation of this method.voidrecord()Records the caller's current stack trace so that theResourceLeakDetectorcan tell where the leaked resource was accessed lastly.voidrecord(java.lang.Object hint)Records the caller's current stack trace and the specified additional arbitrary information so that theResourceLeakDetectorcan tell where the leaked resource was accessed lastly.private voidrecord0(java.lang.Object hint)This method works by exponentially backing off as more records are present in the stack.java.lang.StringtoString()
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Field Detail
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headUpdater
private static final java.util.concurrent.atomic.AtomicReferenceFieldUpdater<ResourceLeakDetector.DefaultResourceLeak<?>,ResourceLeakDetector.Record> headUpdater
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droppedRecordsUpdater
private static final java.util.concurrent.atomic.AtomicIntegerFieldUpdater<ResourceLeakDetector.DefaultResourceLeak<?>> droppedRecordsUpdater
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head
private volatile ResourceLeakDetector.Record head
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droppedRecords
private volatile int droppedRecords
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allLeaks
private final java.util.Set<ResourceLeakDetector.DefaultResourceLeak<?>> allLeaks
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trackedHash
private final int trackedHash
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Constructor Detail
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DefaultResourceLeak
DefaultResourceLeak(java.lang.Object referent, java.lang.ref.ReferenceQueue<java.lang.Object> refQueue, java.util.Set<ResourceLeakDetector.DefaultResourceLeak<?>> allLeaks)
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Method Detail
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record
public void record()
Description copied from interface:ResourceLeakTrackerRecords the caller's current stack trace so that theResourceLeakDetectorcan tell where the leaked resource was accessed lastly. This method is a shortcut torecord(null).- Specified by:
recordin interfaceResourceLeak- Specified by:
recordin interfaceResourceLeakTracker<T>
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record
public void record(java.lang.Object hint)
Description copied from interface:ResourceLeakTrackerRecords the caller's current stack trace and the specified additional arbitrary information so that theResourceLeakDetectorcan tell where the leaked resource was accessed lastly.- Specified by:
recordin interfaceResourceLeak- Specified by:
recordin interfaceResourceLeakTracker<T>
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record0
private void record0(java.lang.Object 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.
ResourceLeakDetector.TARGET_RECORDSaccesses, 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.
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dispose
boolean dispose()
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close
public boolean close()
Description copied from interface:ResourceLeakClose the leak so thatResourceLeakDetectordoes not warn about leaked resources.- Specified by:
closein interfaceResourceLeak- Returns:
trueif called first time,falseif called already
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close
public boolean close(T trackedObject)
Description copied from interface:ResourceLeakTrackerClose the leak so thatResourceLeakTrackerdoes not warn about leaked resources. After this method is called a leak associated with this ResourceLeakTracker should not be reported.- Specified by:
closein interfaceResourceLeakTracker<T>- Returns:
trueif called first time,falseif called already
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reachabilityFence0
private static void reachabilityFence0(java.lang.Object ref)
Ensures that the object referenced by the given reference remains strongly reachable, regardless of any prior actions of the program that might otherwise cause the object to become unreachable; thus, the referenced object is not reclaimable by garbage collection at least until after the invocation of this method.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
ref, not asReference.reachabilityFencefor 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.- Parameters:
ref- the reference. Ifnull, this method has no effect.- See Also:
Reference.reachabilityFence(java.lang.Object)
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toString
public java.lang.String toString()
- Overrides:
toStringin classjava.lang.Object
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