Package com.vaadin.collaborationengine

Class Backend

java.lang.Object

com.vaadin.collaborationengine.Backend

Direct Known Subclasses:

LocalBackend

public abstract class Backend
extends Object

The interface between a cluster backend and Collaboration Engine.

Author:

Vaadin Ltd

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Backend.EventIdNotFoundException	This exception is thrown by the {@link EventLog::subscribe()} method if the provided UUID does not exist in the log.
static interface	Backend.EventLog	A strictly ordered log of submitted events.
static class	Backend.Snapshot	The Snapshot class is used to submit and retrieve a snapshot payload using the {@link Backend::replaceSnapshot()} and {@link Backend::loadLatestSnapshot()} methods.

Constructor Summary

Constructors

Constructor	Description
Backend()

Method Summary

Modifier and Type	Method	Description
abstract Registration	addMembershipListener(MembershipListener membershipListener)	Adds a listener of membership events.
final CollaborationEngine	getCollaborationEngine()	Gets the CollaborationEngine used by this backend.
abstract UUID	getNodeId()	Gets the unique identifier of this backend node.
abstract CompletableFuture<Backend.Snapshot>	loadLatestSnapshot(String name)	Loads the latest snapshot of data identified by the given name.
abstract Backend.EventLog	openEventLog(String logId)	Opens an event log with the given id.
abstract CompletableFuture<Void>	replaceSnapshot(String name, UUID expectedId, UUID newId, String payload)	Submits a snapshot payload of data identified by the given name.
final void	setCollaborationEngine(CollaborationEngine collaborationEngine)	Sets the CollaborationEngine instance for this backend.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Backend

public Backend()

Method Details

getCollaborationEngine

public final CollaborationEngine getCollaborationEngine()

Gets the CollaborationEngine used by this backend.

Returns:

the CollaborationEngine instance, or null if not set

setCollaborationEngine

public final void setCollaborationEngine(CollaborationEngine collaborationEngine)

Sets the CollaborationEngine instance for this backend.

Parameters:

collaborationEngine - the CollaborationEngine instance, not null

openEventLog

public abstract Backend.EventLog openEventLog(String logId)

Opens an event log with the given id. The returned object can be used to capture any common state related to this particular event log. An actual underlying connection is not needed until Backend.EventLog.subscribe(UUID, BiConsumer)} is invoked, but it is still recommended to make this method fail fast in case it would not be possible to open an actual underlying connection later.

Parameters:

logId - the id of the event log to open, not null

Returns:

an object representing the event log, not null

addMembershipListener

public abstract Registration addMembershipListener(MembershipListener membershipListener)

Adds a listener of membership events. The listener will be notified of events dispatched when a node joins or leaves the backend.

Parameters:

membershipListener - the listener, not null

Returns:

a registration that can be used to remove the listener, not null

getNodeId

public abstract UUID getNodeId()

Gets the unique identifier of this backend node.

Returns:

the node id, not null

loadLatestSnapshot

public abstract CompletableFuture<Backend.Snapshot> loadLatestSnapshot(String name)

Loads the latest snapshot of data identified by the given name. To submit a snapshot see replaceSnapshot(String, UUID, UUID, String).

Parameters:

name - the name identifying the data, not null

Returns:

a completable future resolved with the UUID and snapshot, not null

replaceSnapshot

public abstract CompletableFuture<Void> replaceSnapshot(String name,
 UUID expectedId,
 UUID newId,
 String payload)

Submits a snapshot payload of data identified by the given name. The latest submitted snapshot for that name can be loaded with loadLatestSnapshot(String).

Parameters:

name - the name identifying the date, not null

expectedId - the unique ID of the expected current snapshot

newId - the unique ID that the new snapshot will be stored with, not null

payload - the snapshot payload, not null

Returns:

a completable future that will be resolved when the operation completes, not null