io.pravega.client.stream

Interface EventRead<T>

Type Parameters:

T - The type of the event.

public interface EventRead<T>

An event that was read from a stream or a checkpoint marker if one has been requested.

A checkpoint is an indication that the reading application should persist its state to durable storage before reading further. A checkpoint also represents a point where events waiting to be read may be rebalanced among the readers in a group. So before a checkpoint one reader might be handling all of the events sent with routing key X but afterwards it may be a different reader.

Method Summary

Modifier and Type	Method and Description
java.lang.String	getCheckpointName() If a checkpoint has been requested this will return the checkpointName passed to ReaderGroup.initiateCheckpoint(String,ScheduledExecutorService) otherwise this will return null.
T	getEvent() Returns the event that is wrapped in this EventRead or null a timeout occurred or if a checkpoint was requested.
EventPointer	getEventPointer() Returns a pointer object for the event read.
Position	getPosition() The position in the stream that represents where the reader is immediately following this event.
boolean	isCheckpoint() A boolean indicating if this is a checkpoint.

Method Detail

getEvent

T getEvent()

Returns the event that is wrapped in this EventRead or null a timeout occurred or if a checkpoint was requested.

Returns:

The event itself.

getPosition

Position getPosition()

The position in the stream that represents where the reader is immediately following this event. It is useful to store this so that ReaderGroup.readerOffline(String, Position) can be called if the reader dies.

Returns:

Position of the event

getEventPointer

EventPointer getEventPointer()

Returns a pointer object for the event read. The event pointer enables a random read of the event at a future time.

Returns:

Pointer to an event

isCheckpoint

boolean isCheckpoint()

A boolean indicating if this is a checkpoint. In which case getCheckpointName() will be non-null and getEvent() will be null.

Returns:

true if this is a checkpoint.

getCheckpointName

java.lang.String getCheckpointName()

If a checkpoint has been requested this will return the checkpointName passed to ReaderGroup.initiateCheckpoint(String,ScheduledExecutorService) otherwise this will return null.

Returns:

The name of the checkpoint