Package net.i2p.router.util

Class DecayingBloomFilter

java.lang.Object

net.i2p.router.util.DecayingBloomFilter

Direct Known Subclasses:

DecayingHashSet

public class DecayingBloomFilter
extends Object

Series of bloom filters which decay over time, allowing their continual use for time sensitive data. This has a fixed size (per period, using two periods overall), allowing this to pump through hundreds of entries per second with virtually no false positive rate. Down the line, this may be refactored to allow tighter control of the size necessary for the contained bloom filters. See main() for an analysis of false positive rate. See BloomFilterIVValidator for instantiation parameters. See DecayingHashSet for a smaller and simpler version. See net.i2p.router.tunnel.BloomFilterIVValidator

See Also:

DecayingHashSet

Field Summary

Fields

Modifier and Type	Field	Description
protected I2PAppContext	_context
protected long	_currentDuplicates
protected SimpleTimer2.TimedEvent	_decayEvent
protected int	_durationMs
protected int	_entryBytes
protected boolean	_keepDecaying
protected Log	_log
protected String	_name	just for logging
protected ReentrantReadWriteLock	_reorganizeLock	synchronize against this lock when switching double buffers

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	DecayingBloomFilter(int durationMs, int entryBytes, String name, I2PAppContext context)	only for extension by DHS
	DecayingBloomFilter(I2PAppContext context, int durationMs, int entryBytes)	Create a bloom filter that will decay its entries over time.
	DecayingBloomFilter(I2PAppContext context, int durationMs, int entryBytes, String name)	Uses default m of 23, memory usage is 2 MB.
	DecayingBloomFilter(I2PAppContext context, int durationMs, int entryBytes, String name, int m)	Memory usage is 2 * (2**m) bits or 2**(m-2) bytes.

Method Summary

Modifier and Type	Method	Description
boolean	add(byte[] entry)
boolean	add(byte[] entry, int off, int len)
boolean	add(long entry)
void	clear()
protected void	decay()
long	getCurrentDuplicateCount()
double	getFalsePositiveRate()	unsynchronized, only used for logging elsewhere
int	getInsertedCount()	unsynchronized but only used for logging elsewhere
protected void	getReadLock()
protected boolean	getWriteLock()
boolean	isKnown(long entry)
protected void	releaseReadLock()
protected void	releaseWriteLock()
void	stopDecaying()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

_context

protected final I2PAppContext _context

_log

protected final Log _log

_durationMs

protected final int _durationMs

_entryBytes

protected final int _entryBytes

_currentDuplicates

protected long _currentDuplicates

_keepDecaying

protected volatile boolean _keepDecaying

_decayEvent

protected final SimpleTimer2.TimedEvent _decayEvent

_name

protected final String _name

just for logging

_reorganizeLock

protected final ReentrantReadWriteLock _reorganizeLock

synchronize against this lock when switching double buffers

Constructor Detail

DecayingBloomFilter

protected DecayingBloomFilter(int durationMs,
                              int entryBytes,
                              String name,
                              I2PAppContext context)

only for extension by DHS

DecayingBloomFilter

public DecayingBloomFilter(I2PAppContext context,
                           int durationMs,
                           int entryBytes)

Create a bloom filter that will decay its entries over time. Uses default m of 23, memory usage is 2 MB.

Parameters:

durationMs - entries last for at least this long, but no more than twice this long

entryBytes - how large are the entries to be added? if this is less than 32 bytes, the entries added will be expanded by concatenating their XORing against with sufficient random values.

DecayingBloomFilter

public DecayingBloomFilter(I2PAppContext context,
                           int durationMs,
                           int entryBytes,
                           String name)

Uses default m of 23, memory usage is 2 MB.

Parameters:

name - just for logging / debugging / stats

DecayingBloomFilter

public DecayingBloomFilter(I2PAppContext context,
                           int durationMs,
                           int entryBytes,
                           String name,
                           int m)

Memory usage is 2 * (2**m) bits or 2**(m-2) bytes.

Parameters:

m - filter size exponent, max is 29

Method Detail

getCurrentDuplicateCount

public long getCurrentDuplicateCount()

getInsertedCount

public int getInsertedCount()

unsynchronized but only used for logging elsewhere

getFalsePositiveRate

public double getFalsePositiveRate()

unsynchronized, only used for logging elsewhere

add

public boolean add(byte[] entry)

Returns:

true if the entry added is a duplicate

add

public boolean add(byte[] entry,
                   int off,
                   int len)

Returns:

true if the entry added is a duplicate

add

public boolean add(long entry)

Returns:

true if the entry added is a duplicate. the number of low order bits used is determined by the entryBytes parameter used on creation of the filter.

isKnown

public boolean isKnown(long entry)

Returns:

true if the entry is already known. this does NOT add the entry however.

clear

public void clear()

stopDecaying

public void stopDecaying()

decay

protected void decay()

getReadLock

protected void getReadLock()

Since:

0.8.11 moved from DecayingHashSet

releaseReadLock

protected void releaseReadLock()

Since:

0.8.11 moved from DecayingHashSet

getWriteLock

protected boolean getWriteLock()

Returns:

true if the lock was acquired

Since:

0.8.11 moved from DecayingHashSet

releaseWriteLock

protected void releaseWriteLock()

Since:

0.8.11 moved from DecayingHashSet