org.apache.flink.cep.nfa.sharedbuffer

Class SharedBuffer<V>

java.lang.Object

org.apache.flink.cep.nfa.sharedbuffer.SharedBuffer<V>

Type Parameters:

V - Type of the values

public class SharedBuffer<V>
extends Object

A shared buffer implementation which stores values under according state. 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 a buffer for incoming events with unique ids assigned to them. This way we do not need to deserialize events during processing and we store only one copy of the event.

The entries in SharedBuffer are SharedBufferNode. The shared buffer node 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

Constructor Summary

Constructors

Constructor and Description
SharedBuffer(KeyedStateStore stateStore, TypeSerializer<V> valueSerializer)

Method Summary

Modifier and Type	Method and Description
SharedBufferAccessor<V>	getAccessor() Construct an accessor to deal with this sharedBuffer.
int	getEventsBufferCacheSize()
int	getEventsBufferSize()
int	getSharedBufferNodeCacheSize()
int	getSharedBufferNodeSize()
void	init(Map<EventId,Lockable<V>> events, Map<NodeId,Lockable<SharedBufferNode>> entries) Deprecated. Only for state migration!
boolean	isEmpty() Checks if there is no elements in the buffer.

Methods inherited from class java.lang.Object

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

Constructor Detail

SharedBuffer

public SharedBuffer(KeyedStateStore stateStore,
                    TypeSerializer<V> valueSerializer)

Method Detail

init

@Deprecated
public void init(Map<EventId,Lockable<V>> events,
                             Map<NodeId,Lockable<SharedBufferNode>> entries)
                      throws Exception

Deprecated. Only for state migration!

Initializes underlying state with given map of events and entries. Should be used only in case of migration from old state.

Parameters:

events - map of events with assigned unique ids

entries - map of SharedBufferNodes

Throws:

Exception - Thrown if the system cannot access the state.

getAccessor

public SharedBufferAccessor<V> getAccessor()

Construct an accessor to deal with this sharedBuffer.

Returns:

an accessor to deal with this sharedBuffer.

isEmpty

public boolean isEmpty()
                throws Exception

Checks if there is no elements in the buffer.

Returns:

true if there is no elements in the buffer

Throws:

Exception - Thrown if the system cannot access the state.

getEventsBufferCacheSize

@VisibleForTesting
public int getEventsBufferCacheSize()

getEventsBufferSize

@VisibleForTesting
public int getEventsBufferSize()
                                           throws Exception

Throws:

Exception

getSharedBufferNodeSize

@VisibleForTesting
public int getSharedBufferNodeSize()
                                               throws Exception

Throws:

Exception

getSharedBufferNodeCacheSize

@VisibleForTesting
public int getSharedBufferNodeCacheSize()
                                                    throws Exception

Throws:

Exception