Package org.apache.flink.cep.nfa.sharedbuffer

Class SharedBufferAccessor<V>

java.lang.Object

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

All Implemented Interfaces:

AutoCloseable

public class SharedBufferAccessor<V>
extends Object
implements AutoCloseable

Accessor to SharedBuffer that allows operations on the underlying structures in batches. Operations are persisted only after closing the Accessor.

Method Summary

Modifier and Type	Method	Description
void	advanceTime(long timestamp)	Notifies shared buffer that there will be no events with timestamp <&eq; the given value.
void	close()	Persists the entry in the cache to the underlay state.
List<Map<String,List<EventId>>>	extractPatterns(NodeId nodeId, DeweyNumber version)	Returns all elements from the previous relation starting at the given entry.
void	lockNode(NodeId node, DeweyNumber version)	Increases the reference counter for the given entry so that it is not accidentally removed.
Map<String,List<V>>	materializeMatch(Map<String,List<EventId>> match)	Extracts the real event from the sharedBuffer with pre-extracted eventId.
NodeId	put(String stateName, EventId eventId, NodeId previousNodeId, DeweyNumber version)	Stores given value (value + timestamp) under the given state.
EventId	registerEvent(V value, long timestamp)	Adds another unique event to the shared buffer and assigns a unique id for it.
void	releaseEvent(EventId eventId)	Decreases the reference counter for the given event so that it can be removed once the reference counter reaches 0.
void	releaseNode(NodeId node, DeweyNumber version)	Decreases the reference counter for the given entry so that it can be removed once the reference counter reaches 0.

Methods inherited from class java.lang.Object

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

Method Details

advanceTime

public void advanceTime(long timestamp)
                 throws Exception

Notifies shared buffer that there will be no events with timestamp <&eq; the given value. It allows to clear internal counters for number of events seen so far per timestamp.

Parameters:

timestamp - watermark, no earlier events will arrive

Throws:

Exception - Thrown if the system cannot access the state.

registerEvent

public EventId registerEvent(V value,
 long timestamp)
                      throws Exception

Adds another unique event to the shared buffer and assigns a unique id for it. It automatically creates a lock on this event, so it won't be removed during processing of that event. Therefore the lock should be removed after processing all ComputationStates

NOTE:Should be called only once for each unique event!

Parameters:

value - event to be registered

Returns:

unique id of that event that should be used when putting entries to the buffer.

Throws:

Exception - Thrown if the system cannot access the state.

put

public NodeId put(String stateName,
 EventId eventId,
 @Nullable
 NodeId previousNodeId,
 DeweyNumber version)

Stores given value (value + timestamp) under the given state. It assigns a preceding element relation to the previous entry.

Parameters:

stateName - name of the state that the event should be assigned to

eventId - unique id of event assigned by this SharedBuffer

previousNodeId - id of previous entry (might be null if start of new run)

version - Version of the previous relation

Returns:

assigned id of this element

extractPatterns

public List<Map<String,List<EventId>>> extractPatterns(NodeId nodeId,
 DeweyNumber version)

Returns all elements from the previous relation starting at the given entry.

Parameters:

nodeId - id of the starting entry

version - Version of the previous relation which shall be extracted

Returns:

Collection of previous relations starting with the given value

materializeMatch

public Map<String,List<V>> materializeMatch(Map<String,List<EventId>> match)

Extracts the real event from the sharedBuffer with pre-extracted eventId.

Parameters:

match - the matched event's eventId.

Returns:

the event associated with the eventId.

lockNode

public void lockNode(NodeId node,
 DeweyNumber version)

Increases the reference counter for the given entry so that it is not accidentally removed.

Parameters:

node - id of the entry

version - dewey number of the (potential) edge that locks the given node

releaseNode

public void releaseNode(NodeId node,
 DeweyNumber version)
                 throws Exception

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

Parameters:

node - id of the entry

version - dewey number of the (potential) edge that locked the given node

Throws:

Exception - Thrown if the system cannot access the state.

releaseEvent

public void releaseEvent(EventId eventId)
                  throws Exception

Decreases the reference counter for the given event so that it can be removed once the reference counter reaches 0.

Parameters:

eventId - id of the event

Throws:

Exception - Thrown if the system cannot access the state.

close

public void close()
           throws Exception

Persists the entry in the cache to the underlay state.

Specified by:

close in interface AutoCloseable

Throws:

Exception - Thrown if the system cannot access the state.