Interface MessageReplicator.Reader

All Superinterfaces:

AutoCloseable, Closeable, Replicator.Accessor, Replicator.Reader

Enclosing interface:

MessageReplicator

public static interface MessageReplicator.Reader
extends Replicator.Reader

Interface called by any group member for reading committed messages. Readers don't track which messages are applied — applications are responsible for tracking the highest applied position. When an application restarts, it must open the reader at an appropriate position.

See Also:

• newReader

Method Summary

Modifier and Type	Method	Description
byte[]	readMessage()	Blocks until a log message is available, never reading past a commit position or term.
int	readMessage(byte[] buf, int offset, int length)	Blocks until a message is available, and then fully or partially copies it into the given buffer.

Methods inherited from interface Replicator.Accessor

addCommitListener, close, commitPosition, position, term, termEndPosition, termStartPosition, uponCommit, waitForCommit, waitForEndCommit

Modifier and Type	Method	Description
void	addCommitListener(LongConsumer listener)	Install a callback which receives a stream of commit position updates.
void	close()
long	commitPosition()	Returns the current term commit position, which might be lower than the start position.
long	position()	Returns the next log position which will be accessed.
long	term()	Returns the fixed term being accessed.
long	termEndPosition()	Returns the current term end position, which is Long.MAX_VALUE if unbounded.
long	termStartPosition()	Returns the position at the start of the term.
void	uponCommit(long position, LongConsumer task)	Invokes the given task when the commit position reaches the requested position.
long	waitForCommit(long position, long nanosTimeout)	Blocks until the commit position reaches the given position.
default long	waitForEndCommit(long nanosTimeout)	Blocks until the commit position reaches the end of the term.

Method Details

readMessage

byte[] readMessage()
            throws IOException

Blocks until a log message is available, never reading past a commit position or term.

Returns:

complete message or null if the term end has been reached

Throws:

IllegalStateException - if a partially read message remains

InvalidReadException - if log was deleted (position is too low)

IOException

readMessage

int readMessage(byte[] buf,
 int offset,
 int length)
         throws IOException

Blocks until a message is available, and then fully or partially copies it into the given buffer. Messages are partially copied only when the given buffer length is too small. When a message has been fully copied, a positive length is returned. A negative return value indicates the amount of bytes remaining in the message. Compute the ones' complement (~) to determine the actual amount remaining. If the amount remaining is 0 (or -1 when not complemented), then the term end has been reached.

Returns:

message length if positive, or the amount of bytes remaining in the message (ones' complement), or EOF (-1) if the term end has been reached

Throws:

InvalidReadException - if log was deleted (position is too low)

IOException