net.openhft.chronicle.engine.api

Interface EngineReplication

All Superinterfaces:

Replication, View

All Known Implementing Classes:

CMap2EngineReplicator, VanillaEngineReplication

public interface EngineReplication
extends Replication

Author:

Rob Austin.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	EngineReplication.EntryCallback Implemented typically by a replicator, This interface provides the event, which will get called whenever a put() or remove() has occurred to the map
static interface	EngineReplication.ModificationIterator Holds a record of which entries have modification.
static interface	EngineReplication.ModificationNotifier notifies when there is a changed to the modification iterator
static interface	EngineReplication.ReplicationEntry

Method Summary

Modifier and Type	Method and Description
EngineReplication.ModificationIterator	acquireModificationIterator(byte remoteIdentifier) Gets (if it does not exist, creates) an instance of ModificationIterator associated with a remote node, this weak associated is bound using the identifier.
default void	forEach(byte remoteIdentifier, java.util.function.Consumer<EngineReplication.ReplicationEntry> consumer)
byte	identifier() Provides the unique Identifier associated with this instance.
long	lastModificationTime(byte remoteIdentifier) Returns the timestamp of the last change from the specified remote node, already replicated to this host.
void	setLastModificationTime(byte identifier, long timestamp)

Methods inherited from interface net.openhft.chronicle.engine.api.pubsub.Replication

applyReplication

Methods inherited from interface net.openhft.chronicle.engine.api.tree.View

keyedView

Method Detail

identifier

byte identifier()

Provides the unique Identifier associated with this instance.

An identifier is used to determine which replicating node made the change.

If two nodes update their map at the same time with different values, we have to deterministically resolve which update wins, because of eventual consistency both nodes should end up locally holding the same data. Although it is rare two remote nodes could receive an update to their maps at exactly the same time for the same key, we have to handle this edge case, its therefore important not to rely on timestamps alone to reconcile the updates. Typically the update with the newest timestamp should win, but in this example both timestamps are the same, and the decision made to one node should be identical to the decision made to the other. We resolve this simple dilemma by using a node identifier, each node will have a unique identifier, the update from the node with the smallest identifier wins.

Returns:

the unique Identifier associated with this map instance

forEach

default void forEach(byte remoteIdentifier,
                     @NotNull
                     java.util.function.Consumer<EngineReplication.ReplicationEntry> consumer)
              throws InterruptedException

Throws:

InterruptedException

acquireModificationIterator

EngineReplication.ModificationIterator acquireModificationIterator(byte remoteIdentifier)

Gets (if it does not exist, creates) an instance of ModificationIterator associated with a remote node, this weak associated is bound using the identifier.

Specified by:

acquireModificationIterator in interface Replication

Parameters:

remoteIdentifier - the identifier of the remote node

Returns:

the ModificationIterator dedicated for replication to the remote node with the given identifier

See Also:

identifier()

lastModificationTime

long lastModificationTime(byte remoteIdentifier)

Returns the timestamp of the last change from the specified remote node, already replicated to this host.

Used in conjunction with replication, to back fill data from a remote node. This node may have missed updates while it was not been running or connected via TCP.

Specified by:

lastModificationTime in interface Replication

Parameters:

remoteIdentifier - the identifier of the remote node to check last replicated update time from

Returns:

a timestamp of the last modification to an entry, or 0 if there are no entries.

See Also:

identifier()

setLastModificationTime

void setLastModificationTime(byte identifier,
                             long timestamp)