Interface MessageReplicator

All Superinterfaces:

AutoCloseable, Closeable, Replicator

public interface MessageReplicator
extends Replicator

Message-oriented replication interface, which is a bit easier to use than StreamReplicator. Although this replicator has slightly higher overhead, control message passing is handled automatically. Replicas are still required to be reading in order for control messages to be processed, however.

See Also:

• StreamReplicator

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	MessageReplicator.Reader	Interface called by any group member for reading committed messages.
static interface	MessageReplicator.Writer	Interface called by the group leader for proposing messages.

Nested classes/interfaces inherited from interface org.cojen.tupl.repl.Replicator

Replicator.Accessor

Method Summary

Modifier and Type	Method	Description
MessageReplicator.Reader	newReader(long position, boolean follow)	Returns a new reader which accesses data starting from the given position.
MessageReplicator.Writer	newWriter()	Returns a new writer for the leader to write into, or else returns null if the local member isn't the leader.
MessageReplicator.Writer	newWriter(long position)	Returns a new writer for the leader to write into, or else returns null if the local member isn't the leader.
static MessageReplicator	open(ReplicatorConfig config)	Open a MessageReplicator instance, creating it if necessary.

Methods inherited from interface java.io.Closeable

close

Methods inherited from interface org.cojen.tupl.repl.Replicator

commitPosition, compact, connect, encoding, failover, isReadable, localAddress, localMemberId, localRole, requestSnapshot, restore, snapshotRequestAcceptor, socketAcceptor, start, sync, syncCommit

Method Details

open

static MessageReplicator open(ReplicatorConfig config)
                       throws IOException

Open a MessageReplicator instance, creating it if necessary. Be sure to call the start method too.

Throws:

IllegalArgumentException - if misconfigured

IOException

newReader

MessageReplicator.Reader newReader(long position,
 boolean follow)

Returns a new reader which accesses data starting from the given position. The reader returns EOF whenever the end of a term is reached. At the end of a term, try to obtain a new writer to determine if the local member has become the leader.

When passing true for the follow parameter, a reader is always provided at the requested position. When passing false for the follow parameter, null is returned if the current member is the leader for the given position.

Note: Reader instances are not expected to be thread-safe.

Specified by:

newReader in interface Replicator

Parameters:

position - position to start reading from, known to have been committed

follow - pass true to obtain an active reader, even if local member is the leader

Returns:

reader or possibly null when follow is false

Throws:

InvalidReadException - if position is lower than the start position

newWriter

MessageReplicator.Writer newWriter()

Returns a new writer for the leader to write into, or else returns null if the local member isn't the leader. The writer stops accepting messages when the term has ended, and possibly another leader has been elected.

Note: Writer instances are not expected to be thread-safe.

Specified by:

newWriter in interface Replicator

Returns:

writer or null if not the leader

Throws:

IllegalStateException - if an existing writer for the current term already exists

newWriter

MessageReplicator.Writer newWriter(long position)

Returns a new writer for the leader to write into, or else returns null if the local member isn't the leader. The writer stops accepting messages when the term has ended, and possibly another leader has been elected.

Note: Writer instances are not expected to be thread-safe.

Specified by:

newWriter in interface Replicator

Parameters:

position - expected position to start writing from as leader; method returns null if the given position is lower

Returns:

writer or null if not the leader

Throws:

IllegalStateException - if an existing writer for the current term already exists