io.pravega.client.stream

Interface EventStreamReader<T>

Type Parameters:

T - The type of events being sent through this stream.

All Superinterfaces:

java.lang.AutoCloseable

public interface EventStreamReader<T>
extends java.lang.AutoCloseable

A reader for a stream.

This class is safe to use across threads, but doing so will not increase performance.

Method Summary

Modifier and Type	Method and Description
void	close() Close the reader.
T	fetchEvent(EventPointer pointer) Re-read an event that was previously read, by passing the pointer returned from EventRead.getEventPointer().
ReaderConfig	getConfig() Gets the configuration that this reader was created with.
EventRead<T>	readNextEvent(long timeout) Gets the next event in the stream.

Method Detail

readNextEvent

EventRead<T> readNextEvent(long timeout)
                    throws ReinitializationRequiredException,
                           TruncatedDataException

Gets the next event in the stream. If there are no events currently available this will block up for timeout waiting for them to arrive. If none do, an EventRead will be returned with null for EventRead.getEvent(). (As well as for most other fields) An EventRead with null for EventRead.getEvent() is returned when the Reader has read all events up to the configured end StreamCut specified using ReaderGroupConfig.

Parameters:

timeout - An upper bound on how long the call may block before returning null.

Returns:

An instance of EventRead, which contains the next event in the stream. In the case the timeout is reached, EventRead.getEvent() returns null.

Throws:

ReinitializationRequiredException - Is thrown in the event that ReaderGroup.resetReadersToCheckpoint(Checkpoint) or ReaderGroup.resetReaderGroup(ReaderGroupConfig) was called which requires readers to be reinitialized.

TruncatedDataException - if the data that would be read next has been truncated away and can no longer be read. (If following this readNextEvent is called again it will resume from the next available event.)

getConfig

ReaderConfig getConfig()

Gets the configuration that this reader was created with.

Returns:

Reader configuration

fetchEvent

T fetchEvent(EventPointer pointer)
      throws io.pravega.client.segment.impl.NoSuchEventException

Re-read an event that was previously read, by passing the pointer returned from EventRead.getEventPointer(). This does not affect the current position of the reader.

This is a blocking call. Passing invalid offsets has undefined behavior.

Parameters:

pointer - The pointer object to enable a random read of the event.

Returns:

The event at the position specified by the provided pointer or null if the event has been deleted.

Throws:

io.pravega.client.segment.impl.NoSuchEventException - Reader was not able to fetch the event.

close

void close()

Close the reader. No further actions may be performed. If this reader is part of a reader group, this will automatically invoke ReaderGroup.readerOffline(String, Position)

Specified by:

close in interface java.lang.AutoCloseable

See Also:

AutoCloseable.close()