org.apache.flink.cep.nfa

Class SharedBuffer<K extends Serializable,V>

java.lang.Object

org.apache.flink.cep.nfa.SharedBuffer<K,V>

Type Parameters:

K - Type of the keys

V - Type of the values

All Implemented Interfaces:

Serializable

public class SharedBuffer<K extends Serializable,V>
extends Object
implements Serializable

A shared buffer implementation which stores values under a key. Additionally, the values can be versioned such that it is possible to retrieve their predecessor element in the buffer.

The idea of the implementation is to have for each key a dedicated SharedBufferPage. Each buffer page maintains a collection of the inserted values.

The values are wrapped in a SharedBufferEntry. The shared buffer entry allows to store relations between different entries. A dewey versioning scheme allows to discriminate between different relations (e.g. preceding element).

The implementation is strongly based on the paper "Efficient Pattern Matching over Event Streams".

See Also:

https://people.cs.umass.edu/~yanlei/publications/sase-sigmod08.pdf, Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SharedBuffer.SharedBufferSerializer<K extends Serializable,V> A TypeSerializer for the SharedBuffer.
static class	SharedBuffer.SharedBufferSerializerConfigSnapshot<K,V> The TypeSerializerConfigSnapshot serializer configuration to be stored with the managed state.

Constructor Summary

Constructors

Constructor and Description
SharedBuffer(TypeSerializer<V> valueSerializer)

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj)
List<Map<K,List<V>>>	extractPatterns(K key, V value, long timestamp, int counter, DeweyNumber version) Returns all elements from the previous relation starting at the given value with the given key and timestamp.
TypeSerializer<V>	getValueSerializer()
int	hashCode()
boolean	isEmpty()
void	lock(K key, V value, long timestamp, int counter) Increases the reference counter for the given value, key, timestamp entry so that it is not accidentally removed.
boolean	prune(long pruningTimestamp) Deletes all entries in each page which have expired with respect to given pruning timestamp.
int	put(K key, V value, long timestamp, DeweyNumber version) Stores given value (value + timestamp) under the given key.
int	put(K key, V value, long timestamp, K previousKey, V previousValue, long previousTimestamp, int previousCounter, DeweyNumber version) Stores given value (value + timestamp) under the given key.
void	release(K key, V value, long timestamp, int counter) Decreases the reference counter for the given value, key, timestamp entry so that it can be removed once the reference counter reaches 0.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

SharedBuffer

public SharedBuffer(TypeSerializer<V> valueSerializer)

Method Detail

getValueSerializer

public TypeSerializer<V> getValueSerializer()

put

public int put(K key,
               V value,
               long timestamp,
               K previousKey,
               V previousValue,
               long previousTimestamp,
               int previousCounter,
               DeweyNumber version)

Stores given value (value + timestamp) under the given key. It assigns a preceding element relation to the entry which is defined by the previous key, value (value + timestamp).

Parameters:

key - Key of the current value

value - Current value

timestamp - Timestamp of the current value (a value requires always a timestamp to make it uniquely referable))

previousKey - Key of the value for the previous relation

previousValue - Value for the previous relation

previousTimestamp - Timestamp of the value for the previous relation

version - Version of the previous relation

put

public int put(K key,
               V value,
               long timestamp,
               DeweyNumber version)

Stores given value (value + timestamp) under the given key. It assigns no preceding element relation to the entry.

Parameters:

key - Key of the current value

value - Current value

timestamp - Timestamp of the current value (a value requires always a timestamp to make it uniquely referable))

version - Version of the previous relation

isEmpty

public boolean isEmpty()

prune

public boolean prune(long pruningTimestamp)

Deletes all entries in each page which have expired with respect to given pruning timestamp.

Parameters:

pruningTimestamp - The time which is used for pruning. All elements whose timestamp is lower than the pruning timestamp will be removed.

Returns:

true if pruning happened

extractPatterns

public List<Map<K,List<V>>> extractPatterns(K key,
                                            V value,
                                            long timestamp,
                                            int counter,
                                            DeweyNumber version)

Returns all elements from the previous relation starting at the given value with the given key and timestamp.

Parameters:

key - Key of the starting value

value - Value of the starting element

timestamp - Timestamp of the starting value

version - Version of the previous relation which shall be extracted

Returns:

Collection of previous relations starting with the given value

lock

public void lock(K key,
                 V value,
                 long timestamp,
                 int counter)

Increases the reference counter for the given value, key, timestamp entry so that it is not accidentally removed.

Parameters:

key - Key of the value to lock

value - Value to lock

timestamp - Timestamp of the value to lock

release

public void release(K key,
                    V value,
                    long timestamp,
                    int counter)

Decreases the reference counter for the given value, key, timestamp entry so that it can be removed once the reference counter reaches 0.

Parameters:

key - Key of the value to release

value - Value to release

timestamp - Timestamp of the value to release

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object