Package io.netty.util
Class ResourceLeakDetector.DefaultResourceLeak<T>
- All Implemented Interfaces:
ResourceLeak
,ResourceLeakTracker<T>
- Enclosing class:
ResourceLeakDetector<T>
private static final class ResourceLeakDetector.DefaultResourceLeak<T>
extends WeakReference<Object>
implements ResourceLeakTracker<T>, ResourceLeak
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate final Set
<ResourceLeakDetector.DefaultResourceLeak<?>> private int
private static final AtomicIntegerFieldUpdater
<ResourceLeakDetector.DefaultResourceLeak<?>> private ResourceLeakDetector.TraceRecord
private static final AtomicReferenceFieldUpdater
<ResourceLeakDetector.DefaultResourceLeak<?>, ResourceLeakDetector.TraceRecord> private final int
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Constructor Summary
ConstructorsConstructorDescriptionDefaultResourceLeak
(Object referent, ReferenceQueue<Object> refQueue, Set<ResourceLeakDetector.DefaultResourceLeak<?>> allLeaks, Object initialHint) -
Method Summary
Modifier and TypeMethodDescriptionboolean
close()
Close the leak so thatResourceLeakDetector
does not warn about leaked resources.boolean
Close the leak so thatResourceLeakTracker
does not warn about leaked resources.(package private) boolean
dispose()
private String
(package private) String
private static void
reachabilityFence0
(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.void
record()
Records the caller's current stack trace so that theResourceLeakDetector
can tell where the leaked resource was accessed lastly.void
Records the caller's current stack trace and the specified additional arbitrary information so that theResourceLeakDetector
can tell where the leaked resource was accessed lastly.private void
This method works by exponentially backing off as more records are present in the stack.toString()
Methods inherited from class java.lang.ref.Reference
clear, clone, enqueue, get, isEnqueued, reachabilityFence, refersTo
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Field Details
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headUpdater
private static final AtomicReferenceFieldUpdater<ResourceLeakDetector.DefaultResourceLeak<?>,ResourceLeakDetector.TraceRecord> headUpdater -
droppedRecordsUpdater
private static final AtomicIntegerFieldUpdater<ResourceLeakDetector.DefaultResourceLeak<?>> droppedRecordsUpdater -
head
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droppedRecords
private volatile int droppedRecords -
allLeaks
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trackedHash
private final int trackedHash
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Constructor Details
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DefaultResourceLeak
DefaultResourceLeak(Object referent, ReferenceQueue<Object> refQueue, Set<ResourceLeakDetector.DefaultResourceLeak<?>> allLeaks, Object initialHint)
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Method Details
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record
public void record()Description copied from interface:ResourceLeakTracker
Records the caller's current stack trace so that theResourceLeakDetector
can tell where the leaked resource was accessed lastly. This method is a shortcut torecord(null)
.- Specified by:
record
in interfaceResourceLeak
- Specified by:
record
in interfaceResourceLeakTracker<T>
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record
Description copied from interface:ResourceLeakTracker
Records the caller's current stack trace and the specified additional arbitrary information so that theResourceLeakDetector
can tell where the leaked resource was accessed lastly.- Specified by:
record
in interfaceResourceLeak
- Specified by:
record
in interfaceResourceLeakTracker<T>
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record0
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_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. -
dispose
boolean dispose() -
close
public boolean close()Description copied from interface:ResourceLeak
Close the leak so thatResourceLeakDetector
does not warn about leaked resources.- Specified by:
close
in interfaceResourceLeak
- Returns:
true
if called first time,false
if called already
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close
Description copied from interface:ResourceLeakTracker
Close the leak so thatResourceLeakTracker
does not warn about leaked resources. After this method is called a leak associated with this ResourceLeakTracker should not be reported.- Specified by:
close
in interfaceResourceLeakTracker<T>
- Returns:
true
if called first time,false
if called already
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reachabilityFence0
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.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.- Parameters:
ref
- the reference. Ifnull
, this method has no effect.- See Also:
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toString
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getReportAndClearRecords
String getReportAndClearRecords() -
generateReport
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